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The following commit(s) were added to refs/heads/master by this push:
     new 4fd7447f3fc [FLINK-40896][table] Add built-in DEDUPLICATE_KEEP_FIRST 
process table function
4fd7447f3fc is described below

commit 4fd7447f3fcd761c47c1eef84a90afefa0bd8161
Author: Vasudev Kelappassery <[email protected]>
AuthorDate: Tue Oct 27 16:31:13 2026 +0000

    [FLINK-40896][table] Add built-in DEDUPLICATE_KEEP_FIRST process table 
function
    
    This closes #29365.
---
 .../docs/sql/functions/built-in-functions.md       |   1 +
 .../reference/queries/deduplicate-keep-first.md    | 192 +++++++++
 .../docs/sql/functions/built-in-functions.md       |   1 +
 .../reference/queries/deduplicate-keep-first.md    | 192 +++++++++
 .../functions/BuiltInFunctionDefinitions.java      |  25 ++
 .../DeduplicateKeepFirstTypeStrategy.java          | 124 ++++++
 .../stream/DeduplicateKeepFirstRestoreTest.java    |  65 +++
 .../DeduplicateKeepFirstRestoreTestPrograms.java   |  98 +++++
 .../stream/DeduplicateKeepFirstSemanticTests.java  |  50 +++
 .../stream/DeduplicateKeepFirstTestPrograms.java   | 456 +++++++++++++++++++++
 ...cate-keep-first-event-time-pending-restore.json | 352 ++++++++++++++++
 .../savepoint/_metadata                            | Bin 0 -> 18455 bytes
 .../plan/deduplicate-keep-first-keyed-restore.json | 143 +++++++
 .../savepoint/_metadata                            | Bin 0 -> 13722 bytes
 .../functions/ptf/DeduplicateKeepFirst.java        | 258 ++++++++++++
 .../functions/ptf/DeduplicateKeepFirstTest.java    | 174 ++++++++
 16 files changed, 2131 insertions(+)

diff --git a/docs/content.zh/docs/sql/functions/built-in-functions.md 
b/docs/content.zh/docs/sql/functions/built-in-functions.md
index 242cb4b0358..79115623e0a 100644
--- a/docs/content.zh/docs/sql/functions/built-in-functions.md
+++ b/docs/content.zh/docs/sql/functions/built-in-functions.md
@@ -289,6 +289,7 @@ Table functions can be used in two ways: as stand-alone 
inputs, where they are i
 | `FROM_CHANGELOG(input => TABLE t [, ...])` | Converts an append-only table 
with an explicit operation column into a dynamic table. See Changelog 
Conversion for the full list of arguments, semantics, and usage.                
                                                       |
 | `TO_CHANGELOG(input => TABLE t [, ...])`   | Converts a dynamic table into 
an append-only table with an explicit operation column. See Changelog 
Conversion for the full list of arguments, semantics, and usage.                
                                                         |
 | `SNAPSHOT(input => TABLE t [, ...])`       | Returns the current state of a 
dynamic table `t`. `SNAPSHOT` can only be used in a `LATERAL` context and not 
as a stand-alone table function. See [LATERAL SNAPSHOT join]({{< ref 
"docs/sql/reference/queries/joins" >}}#lateral-snapshot-join) for the full list 
of arguments, the join semantics, and usage. |
+| `DEDUPLICATE_KEEP_FIRST(input => TABLE t [, ...])` | Keeps the first record 
per key as an append-only table (first arrival, or earliest event time with 
`on_time`). See [Deduplicate Keep First]({{< ref 
"docs/sql/reference/queries/deduplicate-keep-first" >}}#deduplicate_keep_first) 
for the full list of arguments, semantics, and usage. |
 
 To implement your own table functions, see [user-defined table functions]({{< 
ref "docs/dev/table/functions/udfs" >}}#table-functions).
 
diff --git 
a/docs/content.zh/docs/sql/reference/queries/deduplicate-keep-first.md 
b/docs/content.zh/docs/sql/reference/queries/deduplicate-keep-first.md
new file mode 100644
index 00000000000..4e307552e4f
--- /dev/null
+++ b/docs/content.zh/docs/sql/reference/queries/deduplicate-keep-first.md
@@ -0,0 +1,192 @@
+---
+title: "Deduplicate Keep First"
+weight: 16
+type: docs
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Deduplicate Keep First
+
+{{< label Streaming >}}
+
+Flink SQL provides the `DEDUPLICATE_KEEP_FIRST` process table function (PTF) 
for removing duplicate rows while keeping only the **first** record per key. 
Its output is always **insert-only**, which makes it a concise alternative to 
the `ROW_NUMBER()` [deduplication]({{< ref 
"docs/sql/reference/queries/deduplication" >}}) pattern with more configuration 
options.
+
+| Function | Description |
+|:---------|:------------|
+| [DEDUPLICATE_KEEP_FIRST](#deduplicate_keep_first) | Keeps the first record 
per key as an append-only table (first arrival, or earliest event time with 
`on_time`) |
+
+## DEDUPLICATE_KEEP_FIRST
+
+The `DEDUPLICATE_KEEP_FIRST` PTF keeps the first record per key and drops 
every later record for that key. It supports two ordering modes:
+
+* **Processing time (default):** without `on_time`, the first record 
*observed* for a key is emitted; later records for that key are dropped while 
its state exists. This requires no watermark or event-time attribute.
+* **Event time:** with `on_time`, the record with the *smallest event time* 
per key is kept and emitted once the watermark makes the choice final. A record 
arriving later but carrying an earlier event time replaces the candidate before 
finalization; records that can no longer become the earliest are dropped as 
late.
+
+The input may be an append-only or updating table; the output is append-only 
in every case.
+
+### Syntax
+
+```sql
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE source_table [PARTITION BY (key_col [, key_col2 ...])],
+  [state_ttl => <interval>,]
+  [reset_ttl_on_duplicate => <boolean>,]
+  [on_time => DESCRIPTOR(rowtime_column),]
+  [uid => <string>]
+)
+```
+
+`on_time` and `uid` are system arguments and always come last in the 
signature, which matters when arguments are passed by position.
+
+### Parameters
+
+| Parameter | Required | Description |
+|:----------|:---------|:------------|
+| `input` | Yes | The input table (append-only or updating). Use `PARTITION 
BY` to deduplicate per key; all rows for a key are routed to the same parallel 
instance. Without `PARTITION BY`, the whole input is a single group processed 
at parallelism 1, so only the first row of the entire stream is emitted and 
every later row is dropped regardless of its content. |
+| `state_ttl` | No | An `INTERVAL` giving the processing-time retention for 
the per-key deduplication state. After a key's state expires, a later record 
for that key starts a new deduplication period and may be emitted again. If 
omitted, falls back to `table.exec.state.ttl`; at its default of 0, state is 
retained indefinitely, but a retention can still be introduced later. 
`state_ttl => INTERVAL '0'` also retains state indefinitely, but excludes the 
TTL from the state layout, so a retent [...]
+| `reset_ttl_on_duplicate` | No | Whether a later duplicate refreshes the 
key's `state_ttl`. Defaults to `TRUE`, so retention tracks the most recent 
occurrence of a key. Only meaningful when a TTL applies, whether set through 
`state_ttl` or inherited from `table.exec.state.ttl`. |
+| `on_time` | No | A `DESCRIPTOR` naming a single watermarked column. When 
provided, the row with the smallest event time per key is kept and emitted once 
the watermark passes that timestamp (late rows are dropped). When omitted, the 
function keeps the first row observed for a key (arrival order). Requires 
append-only input; combining `on_time` with an updating input is rejected at 
planning time. |
+| `uid` | No | A unique identifier for the function's state in checkpoints and 
savepoints. Defaults to the function name, so it is required when 
`DEDUPLICATE_KEEP_FIRST` is called more than once in the same job. See [Query 
Evolution with UIDs]({{< ref "docs/dev/table/functions/ptfs" 
>}}#query-evolution-with-uids). |
+
+### Output Schema
+
+When `PARTITION BY` is used, the partition key columns are prepended to the 
output, followed by the remaining (non-key) input columns. In event-time mode a 
rowtime column is appended for (potentially following) time-based operations.
+
+```
+[partition_key_columns] + [remaining_input_columns]
+```
+
+### Examples
+
+#### Keyed keep-first (processing time)
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+The first row for `Vas` is emitted; the later `click` on the same key is 
dropped.
+
+#### Exact duplicates (all columns as key)
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY (user_name, action)
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+```
+
+Partitioning by every column drops only exact duplicate rows while still 
distributing the work across parallel instances.
+
+#### Bounded state with state_ttl
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+-- +I[user_name:'Vas', action:'view']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name,
+  state_ttl => INTERVAL '5' SECOND,
+  reset_ttl_on_duplicate => FALSE
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+`state_ttl` bounds how long per-key state is retained (processing time). While 
the state exists, duplicates are dropped and only the first row per key is 
emitted; after the state expires, a later record for the key starts a new 
deduplication period. With the default `reset_ttl_on_duplicate => TRUE`, each 
dropped duplicate refreshes the retention window; with `FALSE`, retention is 
measured from the first record for the key.
+
+#### Earliest by event time
+
+```sql
+-- Source declares: WATERMARK FOR ts AS ts - INTERVAL '10' SECOND
+-- Input (ts = event time):
+-- +I[user_name:'Vas', action:'login', ts:3.000]
+-- +I[user_name:'Vas', action:'click', ts:1.000]
+-- +I[user_name:'Vas', action:'view',  ts:5.000]
+
+SELECT user_name, action FROM DEDUPLICATE_KEEP_FIRST(
+  input   => TABLE user_events PARTITION BY user_name,
+  on_time => DESCRIPTOR(ts)
+)
+
+-- Output (insert-only, once the watermark finalizes the earliest):
+-- +I[user_name:'Vas', action:'click']
+```
+
+With `on_time`, the record with the smallest event time per key is kept (here 
`click` at `ts 1.000`, not `login` which arrived first) and emitted once the 
watermark passes that timestamp. Late events (i.e. events with timestamp 
smaller or equal to the received watermark) are not taken into consideration.
+
+#### Updating input
+
+```sql
+-- Input (updating changelog):
+-- -D[user_name:'Vas', action:'logout']  key not seen yet         -> ignored
+-- +I[user_name:'Vas', action:'login']   first record for the key -> emitted
+-- +I[user_name:'Vas', action:'login']   duplicate                -> swallowed
+-- -U[user_name:'Vas', action:'login']   retraction               -> swallowed
+-- +U[user_name:'Vas', action:'click']   update                   -> swallowed
+-- -D[user_name:'Vas', action:'click']   delete                   -> swallowed
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+The input may be an [updating changelog]({{< ref 
"docs/dev/table/functions/ptfs" >}}#change-data-capture-basics) containing 
inserts (`+I`), update-befores (`-U`), update-afters (`+U`), and deletes 
(`-D`). `DEDUPLICATE_KEEP_FIRST` keeps the first `+I` or `+U` observed per key 
and swallows every later change to that key (duplicate, `-U`, `+U`, `-D`), so 
the output stays insert-only. A `-U` or `-D` for a key that has not been seen 
yet is ignored and does not mark the key as seen, so the nex [...]
+
+#### Table API
+
+```java
+Table userEvents = ...;
+
+// Keep the first row per key (processing time).
+Table result = 
userEvents.partitionBy($("user_name")).process("DEDUPLICATE_KEEP_FIRST");
+
+// With optional arguments.
+Table result = userEvents
+    .partitionBy($("user_name"))
+    .process(
+        "DEDUPLICATE_KEEP_FIRST",
+        lit(Duration.ofSeconds(5)).asArgument("state_ttl"),
+        lit(false).asArgument("reset_ttl_on_duplicate"));
+```
+
+{{< top >}}
diff --git a/docs/content/docs/sql/functions/built-in-functions.md 
b/docs/content/docs/sql/functions/built-in-functions.md
index 40b54b2869b..01bf2070579 100644
--- a/docs/content/docs/sql/functions/built-in-functions.md
+++ b/docs/content/docs/sql/functions/built-in-functions.md
@@ -292,6 +292,7 @@ Table functions can be used in two ways: as stand-alone 
inputs, where they are i
 | `FROM_CHANGELOG(input => TABLE t [, ...])` | Converts an append-only table 
with an explicit operation column into a dynamic table. See [Changelog 
Conversion]({{< ref "docs/sql/reference/queries/changelog" >}}#from_changelog) 
for the full list of arguments, semantics, and usage.                           
                                            |
 | `TO_CHANGELOG(input => TABLE t [, ...])`   | Converts a dynamic table into 
an append-only table with an explicit operation column. See [Changelog 
Conversion]({{< ref "docs/sql/reference/queries/changelog" >}}#to_changelog) 
for the full list of arguments, semantics, and usage.                           
                                              |
 | `SNAPSHOT(input => TABLE t [, ...])`       | Returns the current state of a 
dynamic table `t`. `SNAPSHOT` can only be used in a `LATERAL` context and not 
as a stand-alone table function. See [LATERAL SNAPSHOT join]({{< ref 
"docs/sql/reference/queries/joins" >}}#lateral-snapshot-join) for the full list 
of arguments, the join semantics, and usage. |
+| `DEDUPLICATE_KEEP_FIRST(input => TABLE t [, ...])` | Keeps the first record 
per key as an append-only table (first arrival, or earliest event time with 
`on_time`). See [Deduplicate Keep First]({{< ref 
"docs/sql/reference/queries/deduplicate-keep-first" >}}#deduplicate_keep_first) 
for the full list of arguments, semantics, and usage. |
 
 To implement your own table functions, see [user-defined table functions]({{< 
ref "docs/dev/table/functions/udfs" >}}#table-functions).
 
diff --git a/docs/content/docs/sql/reference/queries/deduplicate-keep-first.md 
b/docs/content/docs/sql/reference/queries/deduplicate-keep-first.md
new file mode 100644
index 00000000000..4e307552e4f
--- /dev/null
+++ b/docs/content/docs/sql/reference/queries/deduplicate-keep-first.md
@@ -0,0 +1,192 @@
+---
+title: "Deduplicate Keep First"
+weight: 16
+type: docs
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Deduplicate Keep First
+
+{{< label Streaming >}}
+
+Flink SQL provides the `DEDUPLICATE_KEEP_FIRST` process table function (PTF) 
for removing duplicate rows while keeping only the **first** record per key. 
Its output is always **insert-only**, which makes it a concise alternative to 
the `ROW_NUMBER()` [deduplication]({{< ref 
"docs/sql/reference/queries/deduplication" >}}) pattern with more configuration 
options.
+
+| Function | Description |
+|:---------|:------------|
+| [DEDUPLICATE_KEEP_FIRST](#deduplicate_keep_first) | Keeps the first record 
per key as an append-only table (first arrival, or earliest event time with 
`on_time`) |
+
+## DEDUPLICATE_KEEP_FIRST
+
+The `DEDUPLICATE_KEEP_FIRST` PTF keeps the first record per key and drops 
every later record for that key. It supports two ordering modes:
+
+* **Processing time (default):** without `on_time`, the first record 
*observed* for a key is emitted; later records for that key are dropped while 
its state exists. This requires no watermark or event-time attribute.
+* **Event time:** with `on_time`, the record with the *smallest event time* 
per key is kept and emitted once the watermark makes the choice final. A record 
arriving later but carrying an earlier event time replaces the candidate before 
finalization; records that can no longer become the earliest are dropped as 
late.
+
+The input may be an append-only or updating table; the output is append-only 
in every case.
+
+### Syntax
+
+```sql
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE source_table [PARTITION BY (key_col [, key_col2 ...])],
+  [state_ttl => <interval>,]
+  [reset_ttl_on_duplicate => <boolean>,]
+  [on_time => DESCRIPTOR(rowtime_column),]
+  [uid => <string>]
+)
+```
+
+`on_time` and `uid` are system arguments and always come last in the 
signature, which matters when arguments are passed by position.
+
+### Parameters
+
+| Parameter | Required | Description |
+|:----------|:---------|:------------|
+| `input` | Yes | The input table (append-only or updating). Use `PARTITION 
BY` to deduplicate per key; all rows for a key are routed to the same parallel 
instance. Without `PARTITION BY`, the whole input is a single group processed 
at parallelism 1, so only the first row of the entire stream is emitted and 
every later row is dropped regardless of its content. |
+| `state_ttl` | No | An `INTERVAL` giving the processing-time retention for 
the per-key deduplication state. After a key's state expires, a later record 
for that key starts a new deduplication period and may be emitted again. If 
omitted, falls back to `table.exec.state.ttl`; at its default of 0, state is 
retained indefinitely, but a retention can still be introduced later. 
`state_ttl => INTERVAL '0'` also retains state indefinitely, but excludes the 
TTL from the state layout, so a retent [...]
+| `reset_ttl_on_duplicate` | No | Whether a later duplicate refreshes the 
key's `state_ttl`. Defaults to `TRUE`, so retention tracks the most recent 
occurrence of a key. Only meaningful when a TTL applies, whether set through 
`state_ttl` or inherited from `table.exec.state.ttl`. |
+| `on_time` | No | A `DESCRIPTOR` naming a single watermarked column. When 
provided, the row with the smallest event time per key is kept and emitted once 
the watermark passes that timestamp (late rows are dropped). When omitted, the 
function keeps the first row observed for a key (arrival order). Requires 
append-only input; combining `on_time` with an updating input is rejected at 
planning time. |
+| `uid` | No | A unique identifier for the function's state in checkpoints and 
savepoints. Defaults to the function name, so it is required when 
`DEDUPLICATE_KEEP_FIRST` is called more than once in the same job. See [Query 
Evolution with UIDs]({{< ref "docs/dev/table/functions/ptfs" 
>}}#query-evolution-with-uids). |
+
+### Output Schema
+
+When `PARTITION BY` is used, the partition key columns are prepended to the 
output, followed by the remaining (non-key) input columns. In event-time mode a 
rowtime column is appended for (potentially following) time-based operations.
+
+```
+[partition_key_columns] + [remaining_input_columns]
+```
+
+### Examples
+
+#### Keyed keep-first (processing time)
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+The first row for `Vas` is emitted; the later `click` on the same key is 
dropped.
+
+#### Exact duplicates (all columns as key)
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY (user_name, action)
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+```
+
+Partitioning by every column drops only exact duplicate rows while still 
distributing the work across parallel instances.
+
+#### Bounded state with state_ttl
+
+```sql
+-- Input (append-only):
+-- +I[user_name:'Vas', action:'login']
+-- +I[user_name:'Vas', action:'click']
+-- +I[user_name:'Vas', action:'view']
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name,
+  state_ttl => INTERVAL '5' SECOND,
+  reset_ttl_on_duplicate => FALSE
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+`state_ttl` bounds how long per-key state is retained (processing time). While 
the state exists, duplicates are dropped and only the first row per key is 
emitted; after the state expires, a later record for the key starts a new 
deduplication period. With the default `reset_ttl_on_duplicate => TRUE`, each 
dropped duplicate refreshes the retention window; with `FALSE`, retention is 
measured from the first record for the key.
+
+#### Earliest by event time
+
+```sql
+-- Source declares: WATERMARK FOR ts AS ts - INTERVAL '10' SECOND
+-- Input (ts = event time):
+-- +I[user_name:'Vas', action:'login', ts:3.000]
+-- +I[user_name:'Vas', action:'click', ts:1.000]
+-- +I[user_name:'Vas', action:'view',  ts:5.000]
+
+SELECT user_name, action FROM DEDUPLICATE_KEEP_FIRST(
+  input   => TABLE user_events PARTITION BY user_name,
+  on_time => DESCRIPTOR(ts)
+)
+
+-- Output (insert-only, once the watermark finalizes the earliest):
+-- +I[user_name:'Vas', action:'click']
+```
+
+With `on_time`, the record with the smallest event time per key is kept (here 
`click` at `ts 1.000`, not `login` which arrived first) and emitted once the 
watermark passes that timestamp. Late events (i.e. events with timestamp 
smaller or equal to the received watermark) are not taken into consideration.
+
+#### Updating input
+
+```sql
+-- Input (updating changelog):
+-- -D[user_name:'Vas', action:'logout']  key not seen yet         -> ignored
+-- +I[user_name:'Vas', action:'login']   first record for the key -> emitted
+-- +I[user_name:'Vas', action:'login']   duplicate                -> swallowed
+-- -U[user_name:'Vas', action:'login']   retraction               -> swallowed
+-- +U[user_name:'Vas', action:'click']   update                   -> swallowed
+-- -D[user_name:'Vas', action:'click']   delete                   -> swallowed
+
+SELECT * FROM DEDUPLICATE_KEEP_FIRST(
+  input => TABLE user_events PARTITION BY user_name
+)
+
+-- Output (insert-only):
+-- +I[user_name:'Vas', action:'login']
+```
+
+The input may be an [updating changelog]({{< ref 
"docs/dev/table/functions/ptfs" >}}#change-data-capture-basics) containing 
inserts (`+I`), update-befores (`-U`), update-afters (`+U`), and deletes 
(`-D`). `DEDUPLICATE_KEEP_FIRST` keeps the first `+I` or `+U` observed per key 
and swallows every later change to that key (duplicate, `-U`, `+U`, `-D`), so 
the output stays insert-only. A `-U` or `-D` for a key that has not been seen 
yet is ignored and does not mark the key as seen, so the nex [...]
+
+#### Table API
+
+```java
+Table userEvents = ...;
+
+// Keep the first row per key (processing time).
+Table result = 
userEvents.partitionBy($("user_name")).process("DEDUPLICATE_KEEP_FIRST");
+
+// With optional arguments.
+Table result = userEvents
+    .partitionBy($("user_name"))
+    .process(
+        "DEDUPLICATE_KEEP_FIRST",
+        lit(Duration.ofSeconds(5)).asArgument("state_ttl"),
+        lit(false).asArgument("reset_ttl_on_duplicate"));
+```
+
+{{< top >}}
diff --git 
a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java
 
b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java
index 9e993e26429..6c09b633d81 100644
--- 
a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java
+++ 
b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java
@@ -38,6 +38,7 @@ import 
org.apache.flink.table.types.inference.StaticArgumentTrait;
 import org.apache.flink.table.types.inference.TraitCondition;
 import org.apache.flink.table.types.inference.TypeStrategies;
 import 
org.apache.flink.table.types.inference.strategies.ArrayOfStringArgumentTypeStrategy;
+import 
org.apache.flink.table.types.inference.strategies.DeduplicateKeepFirstTypeStrategy;
 import 
org.apache.flink.table.types.inference.strategies.FromChangelogTypeStrategy;
 import 
org.apache.flink.table.types.inference.strategies.SpecificInputTypeStrategies;
 import 
org.apache.flink.table.types.inference.strategies.SpecificTypeStrategies;
@@ -939,6 +940,30 @@ public final class BuiltInFunctionDefinitions {
                             
"org.apache.flink.table.runtime.functions.ptf.FromChangelogFunction")
                     .build();
 
+    public static final BuiltInFunctionDefinition DEDUPLICATE_KEEP_FIRST =
+            BuiltInFunctionDefinition.newBuilder()
+                    .name("DEDUPLICATE_KEEP_FIRST")
+                    .kind(PROCESS_TABLE)
+                    .staticArguments(
+                            StaticArgument.table(
+                                    "input",
+                                    Row.class,
+                                    false,
+                                    EnumSet.of(
+                                            StaticArgumentTrait.TABLE,
+                                            
StaticArgumentTrait.SET_SEMANTIC_TABLE,
+                                            
StaticArgumentTrait.OPTIONAL_PARTITION_BY,
+                                            
StaticArgumentTrait.SUPPORT_UPDATES)),
+                            StaticArgument.scalar(
+                                    "state_ttl", 
DataTypes.INTERVAL(DataTypes.SECOND()), true),
+                            StaticArgument.scalar(
+                                    "reset_ttl_on_duplicate", 
DataTypes.BOOLEAN(), true))
+                    
.inputTypeStrategy(DeduplicateKeepFirstTypeStrategy.INPUT_TYPE_STRATEGY)
+                    
.outputTypeStrategy(DeduplicateKeepFirstTypeStrategy.OUTPUT_TYPE_STRATEGY)
+                    .runtimeClass(
+                            
"org.apache.flink.table.runtime.functions.ptf.DeduplicateKeepFirst")
+                    .build();
+
     /**
      * Built-in proxy function for the LATERAL SNAPSHOT temporal join.
      *
diff --git 
a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/inference/strategies/DeduplicateKeepFirstTypeStrategy.java
 
b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/inference/strategies/DeduplicateKeepFirstTypeStrategy.java
new file mode 100644
index 00000000000..3ea1167da87
--- /dev/null
+++ 
b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/inference/strategies/DeduplicateKeepFirstTypeStrategy.java
@@ -0,0 +1,124 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.types.inference.strategies;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.table.api.DataTypes;
+import org.apache.flink.table.api.DataTypes.Field;
+import org.apache.flink.table.api.ValidationException;
+import org.apache.flink.table.functions.TableSemantics;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.inference.CallContext;
+import org.apache.flink.table.types.inference.InputTypeStrategy;
+import org.apache.flink.table.types.inference.TypeStrategy;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+/** Type strategies for the {@code DEDUPLICATE_KEEP_FIRST} process table 
function. */
+@Internal
+public final class DeduplicateKeepFirstTypeStrategy {
+
+    public static final int ARG_INPUT = 0;
+    public static final int ARG_STATE_TTL = 1;
+    public static final int ARG_RESET_TTL_ON_DUPLICATE = 2;
+
+    public static final InputTypeStrategy INPUT_TYPE_STRATEGY =
+            new ValidationOnlyInputTypeStrategy() {
+                @Override
+                public Optional<List<DataType>> inferInputTypes(
+                        final CallContext callContext, final boolean 
throwOnFailure) {
+                    final Optional<List<DataType>> stateTtlError =
+                            validateStateTtl(callContext, throwOnFailure);
+                    if (stateTtlError.isPresent()) {
+                        return stateTtlError;
+                    }
+
+                    final Optional<List<DataType>> resetTtlError =
+                            validateResetTtlOnDuplicate(callContext, 
throwOnFailure);
+                    if (resetTtlError.isPresent()) {
+                        return resetTtlError;
+                    }
+
+                    return Optional.of(callContext.getArgumentDataTypes());
+                }
+            };
+
+    public static final TypeStrategy OUTPUT_TYPE_STRATEGY =
+            callContext -> {
+                final TableSemantics tableSemantics =
+                        callContext
+                                .getTableSemantics(ARG_INPUT)
+                                .orElseThrow(
+                                        () ->
+                                                new ValidationException(
+                                                        "First argument must 
be a table for DEDUPLICATE_KEEP_FIRST."));
+
+                final List<Field> inputFields = 
DataType.getFields(tableSemantics.dataType());
+                final List<Field> outputFields =
+                        Arrays.stream(
+                                        
ChangelogTypeStrategyUtils.computeOutputIndices(
+                                                tableSemantics))
+                                .mapToObj(inputFields::get)
+                                .collect(Collectors.toList());
+                return Optional.of(DataTypes.ROW(outputFields).notNull());
+            };
+
+    private static Optional<List<DataType>> validateStateTtl(
+            final CallContext callContext, final boolean throwOnFailure) {
+        if (callContext.isArgumentNull(ARG_STATE_TTL)) {
+            return Optional.empty();
+        }
+        if (!callContext.isArgumentLiteral(ARG_STATE_TTL)) {
+            return callContext.fail(
+                    throwOnFailure,
+                    "The 'state_ttl' argument must be a constant INTERVAL 
literal.");
+        }
+        final Optional<Duration> stateTtl =
+                callContext.getArgumentValue(ARG_STATE_TTL, Duration.class);
+        if (stateTtl.isPresent() && stateTtl.get().isNegative()) {
+            return callContext.fail(
+                    throwOnFailure,
+                    "The 'state_ttl' argument must not be negative, but was 
'%s'. "
+                            + "Use a positive INTERVAL to bound state 
retention, INTERVAL '0' to "
+                            + "retain state indefinitely without a TTL, or 
omit the argument to "
+                            + "fall back to session defaults.",
+                    stateTtl.get());
+        }
+        return Optional.empty();
+    }
+
+    private static Optional<List<DataType>> validateResetTtlOnDuplicate(
+            final CallContext callContext, final boolean throwOnFailure) {
+        if (callContext.isArgumentNull(ARG_RESET_TTL_ON_DUPLICATE)) {
+            return Optional.empty();
+        }
+        if (!callContext.isArgumentLiteral(ARG_RESET_TTL_ON_DUPLICATE)) {
+            return callContext.fail(
+                    throwOnFailure,
+                    "The 'reset_ttl_on_duplicate' argument must be a constant 
BOOLEAN literal.");
+        }
+        return Optional.empty();
+    }
+
+    private DeduplicateKeepFirstTypeStrategy() {}
+}
diff --git 
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTest.java
 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTest.java
new file mode 100644
index 00000000000..fa9ad95f085
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTest.java
@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.plan.nodes.exec.stream;
+
+import org.apache.flink.table.planner.factories.TestValuesTableFactory;
+import 
org.apache.flink.table.planner.plan.nodes.exec.testutils.RestoreTestBase;
+import org.apache.flink.table.test.program.SourceTestStep;
+import org.apache.flink.table.test.program.TableTestProgram;
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+/** Restore tests for the built-in DEDUPLICATE_KEEP_FIRST PTF. */
+public class DeduplicateKeepFirstRestoreTest extends RestoreTestBase {
+
+    // Bounds the wait for the pending-candidate savepoint trigger so a stuck 
source fails fast.
+    private static final long SAVEPOINT_READY_TIMEOUT_MILLIS = 
TimeUnit.MINUTES.toMillis(5);
+
+    public DeduplicateKeepFirstRestoreTest() {
+        super(StreamExecProcessTableFunction.class);
+    }
+
+    @Override
+    public List<TableTestProgram> programs() {
+        return List.of(
+                DeduplicateKeepFirstRestoreTestPrograms.KEYED_RESTORE,
+                
DeduplicateKeepFirstRestoreTestPrograms.EVENT_TIME_PENDING_RESTORE);
+    }
+
+    @Override
+    protected void awaitSavepointReady(TableTestProgram program, 
List<CompletableFuture<?>> futures)
+            throws Exception {
+        if (program != 
DeduplicateKeepFirstRestoreTestPrograms.EVENT_TIME_PENDING_RESTORE) {
+            super.awaitSavepointReady(program, futures);
+            return;
+        }
+        // The candidate is buffered but not emitted before restore, so there 
is no sink output to
+        // gate on. Instead wait until the source has emitted its 
before-restore rows;
+        // stop-with-savepoint then drains them into keyed state before 
snapshotting.
+        for (SourceTestStep source : program.getSetupSourceTestSteps()) {
+            final int count = source.dataBeforeRestore.size();
+            if (count > 0) {
+                TestValuesTableFactory.awaitSourceEmitted(source.name, count)
+                        .get(SAVEPOINT_READY_TIMEOUT_MILLIS, 
TimeUnit.MILLISECONDS);
+            }
+        }
+    }
+}
diff --git 
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTestPrograms.java
 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTestPrograms.java
new file mode 100644
index 00000000000..f33d91892d0
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstRestoreTestPrograms.java
@@ -0,0 +1,98 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.plan.nodes.exec.stream;
+
+import org.apache.flink.table.test.program.SinkTestStep;
+import org.apache.flink.table.test.program.SourceTestStep;
+import org.apache.flink.table.test.program.TableTestProgram;
+import org.apache.flink.types.Row;
+import org.apache.flink.types.RowKind;
+
+import java.time.Instant;
+
+/** Restore {@link TableTestProgram}s for the built-in DEDUPLICATE_KEEP_FIRST 
PTF. */
+public class DeduplicateKeepFirstRestoreTestPrograms {
+
+    private static final String[] USER_EVENTS_SCHEMA = {"user_name STRING", 
"action STRING"};
+
+    private static final String[] TIMED_EVENTS_SCHEMA = {
+        "user_name STRING",
+        "action STRING",
+        "ts TIMESTAMP_LTZ(3)",
+        "WATERMARK FOR ts AS ts - INTERVAL '0.001' SECOND"
+    };
+
+    public static final TableTestProgram KEYED_RESTORE =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-keyed-restore",
+                            "the keep-first 'seen' state restores via compiled 
plan + savepoint: "
+                                    + "an already-seen key stays deduplicated 
after restore, and a "
+                                    + "key first observed after restore is 
emitted")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedBeforeRestore(
+                                            Row.of("Vas", "login"), 
Row.of("Vas", "click"))
+                                    .producedAfterRestore(
+                                            Row.of("Vas", "logout"), 
Row.of("Alice", "hello"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedBeforeRestore(
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"))
+                                    .consumedAfterRestore(
+                                            Row.ofKind(RowKind.INSERT, 
"Alice", "hello"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram EVENT_TIME_PENDING_RESTORE =
+            TableTestProgram.of(
+                            
"deduplicate-keep-first-event-time-pending-restore",
+                            "an event-time candidate buffered but not yet 
finalized (its timer has "
+                                    + "not fired) survives the savepoint: 
after restore, the "
+                                    + "watermark advances and the buffered 
candidate is emitted")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(TIMED_EVENTS_SCHEMA)
+                                    .producedBeforeRestore(
+                                            Row.of("Bob", "first", 
Instant.ofEpochMilli(5)),
+                                            Row.of("Alice", "first", 
Instant.ofEpochMilli(5)),
+                                            Row.of("Carol", "first", 
Instant.ofEpochMilli(5)))
+                                    .producedAfterRestore(
+                                            Row.of("Bob", "later", 
Instant.ofEpochMilli(100)))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedBeforeRestore(new Row[0])
+                                    .consumedAfterRestore(
+                                            Row.ofKind(RowKind.INSERT, "Bob", 
"first"),
+                                            Row.ofKind(RowKind.INSERT, 
"Alice", "first"),
+                                            Row.ofKind(RowKind.INSERT, 
"Carol", "first"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT user_name, action FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "on_time => DESCRIPTOR(ts))")
+                    .build();
+}
diff --git 
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstSemanticTests.java
 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstSemanticTests.java
new file mode 100644
index 00000000000..89e8367cee4
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstSemanticTests.java
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.plan.nodes.exec.stream;
+
+import 
org.apache.flink.table.planner.plan.nodes.exec.testutils.SemanticTestBase;
+import org.apache.flink.table.test.program.TableTestProgram;
+
+import java.util.List;
+
+/** Semantic tests for the built-in DEDUPLICATE_KEEP_FIRST process table 
function. */
+public class DeduplicateKeepFirstSemanticTests extends SemanticTestBase {
+
+    @Override
+    public List<TableTestProgram> programs() {
+        return List.of(
+                DeduplicateKeepFirstTestPrograms.KEYED,
+                DeduplicateKeepFirstTestPrograms.MULTI_KEY,
+                DeduplicateKeepFirstTestPrograms.MULTI_COLUMN_KEY,
+                DeduplicateKeepFirstTestPrograms.NULL_KEY,
+                DeduplicateKeepFirstTestPrograms.NO_PARTITION_BY,
+                DeduplicateKeepFirstTestPrograms.RESET_WITH_ZERO_TTL,
+                DeduplicateKeepFirstTestPrograms.NO_TTL_RESET,
+                DeduplicateKeepFirstTestPrograms.WHOLE_ROW_KEY,
+                DeduplicateKeepFirstTestPrograms.EVENT_TIME,
+                
DeduplicateKeepFirstTestPrograms.EVENT_TIME_CANDIDATE_FIELD_NAMES,
+                DeduplicateKeepFirstTestPrograms.EVENT_TIME_LATE_DROPPED,
+                DeduplicateKeepFirstTestPrograms.UPDATING_INPUT,
+                DeduplicateKeepFirstTestPrograms.UNSEEN_RETRACTION_IGNORED,
+                DeduplicateKeepFirstTestPrograms.UPDATING_EVENT_TIME_FAILS,
+                DeduplicateKeepFirstTestPrograms.NEGATIVE_TTL_FAILS,
+                DeduplicateKeepFirstTestPrograms.NON_LITERAL_TTL_FAILS,
+                DeduplicateKeepFirstTestPrograms.NON_LITERAL_RESET_FAILS);
+    }
+}
diff --git 
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstTestPrograms.java
 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstTestPrograms.java
new file mode 100644
index 00000000000..2ecebb7e798
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/nodes/exec/stream/DeduplicateKeepFirstTestPrograms.java
@@ -0,0 +1,456 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.planner.plan.nodes.exec.stream;
+
+import org.apache.flink.table.api.ValidationException;
+import org.apache.flink.table.test.program.SinkTestStep;
+import org.apache.flink.table.test.program.SourceTestStep;
+import org.apache.flink.table.test.program.TableTestProgram;
+import org.apache.flink.types.Row;
+import org.apache.flink.types.RowKind;
+
+import java.time.Instant;
+
+/** {@link TableTestProgram} definitions for testing the built-in 
DEDUPLICATE_KEEP_FIRST PTF. */
+public class DeduplicateKeepFirstTestPrograms {
+
+    private static final String[] USER_EVENTS_SCHEMA = {"user_name STRING", 
"action STRING"};
+
+    private static final String[] TIMED_EVENTS_SCHEMA = {
+        "user_name STRING",
+        "action STRING",
+        "ts TIMESTAMP_LTZ(3)",
+        "WATERMARK FOR ts AS ts - INTERVAL '10' SECOND"
+    };
+
+    public static final TableTestProgram KEYED =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-keyed",
+                            "only the first row per PARTITION BY key is 
emitted")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(Row.of("Vas", "login"), 
Row.of("Vas", "click"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram MULTI_KEY =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-multi-key",
+                            "each PARTITION BY key keeps its own first row, 
independently of "
+                                    + "interleaving with other keys")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login"),
+                                            Row.of("Alice", "click"),
+                                            Row.of("Vas", "click"),
+                                            Row.of("Alice", "view"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"),
+                                            Row.ofKind(RowKind.INSERT, 
"Alice", "click"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram MULTI_COLUMN_KEY =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-multi-column-key",
+                            "a multi-column PARTITION BY keeps the first row 
per composite key; "
+                                    + "rows differing in either key column 
form distinct groups")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema("region STRING", "user_name 
STRING", "action STRING")
+                                    .producedValues(
+                                            Row.of("EU", "Vas", "login"),
+                                            Row.of("EU", "Vas", "click"),
+                                            Row.of("US", "Vas", "signup"),
+                                            Row.of("EU", "Alice", "view"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema("user_name STRING", "region 
STRING", "action STRING")
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"EU", "login"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"US", "signup"),
+                                            Row.ofKind(RowKind.INSERT, 
"Alice", "EU", "view"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
"
+                                    + "(user_name, region))")
+                    .build();
+
+    public static final TableTestProgram NULL_KEY =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-null-key",
+                            "a NULL PARTITION BY key forms its own dedup 
group, keeping only "
+                                    + "its first row")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of(null, "login"),
+                                            Row.of("Vas", "click"),
+                                            Row.of(null, "click"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, null, 
"login"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"click"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram NO_PARTITION_BY =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-no-partition-by",
+                            "without PARTITION BY the whole input is one 
group: only the "
+                                    + "very first row is emitted, regardless 
of its content")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login"),
+                                            Row.of("Alice", "click"),
+                                            Row.of("Bob", "view"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST(input => TABLE user_events)")
+                    .build();
+
+    public static final TableTestProgram RESET_WITH_ZERO_TTL =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-reset-with-zero-ttl",
+                            "reset_ttl_on_duplicate=TRUE with 
state_ttl=INTERVAL '0' (TTL "
+                                    + "disabled): only the first row per key 
is emitted")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login"),
+                                            Row.of("Vas", "click"),
+                                            Row.of("Vas", "view"),
+                                            Row.of("Vas", "logout"),
+                                            Row.of("Vas", "login"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "state_ttl => INTERVAL '0' SECOND, "
+                                    + "reset_ttl_on_duplicate => TRUE)")
+                    .build();
+
+    public static final TableTestProgram NO_TTL_RESET =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-no-ttl-reset",
+                            "reset_ttl_on_duplicate=FALSE still emits only the 
first row per key")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login"),
+                                            Row.of("Vas", "click"),
+                                            Row.of("Vas", "view"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "state_ttl => INTERVAL '5' SECOND, "
+                                    + "reset_ttl_on_duplicate => FALSE)")
+                    .build();
+
+    public static final TableTestProgram WHOLE_ROW_KEY =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-whole-row-key",
+                            "PARTITION BY over every column deduplicates 
exact-duplicate rows, "
+                                    + "keeping one row per distinct payload")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login"),
+                                            Row.of("Vas", "login"),
+                                            Row.of("Vas", "click"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"click"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
(user_name, action))")
+                    .build();
+
+    public static final TableTestProgram EVENT_TIME =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-event-time",
+                            "with on_time, the row with the smallest event 
time is kept per key, "
+                                    + "not the first to arrive")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(TIMED_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Vas", "login", 
Instant.ofEpochMilli(3000)),
+                                            Row.of("Vas", "click", 
Instant.ofEpochMilli(1000)),
+                                            Row.of("Vas", "view", 
Instant.ofEpochMilli(5000)))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema("user_name STRING", "action 
STRING")
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "click"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT user_name, action FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "on_time => DESCRIPTOR(ts))")
+                    .build();
+
+    public static final TableTestProgram EVENT_TIME_CANDIDATE_FIELD_NAMES =
+            TableTestProgram.of(
+                            
"deduplicate-keep-first-event-time-candidate-field-names",
+                            "with on_time, input columns named like the 
buffered candidate's "
+                                    + "fields are emitted unchanged for the 
earliest row")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(
+                                            "user_name STRING",
+                                            "payload STRING",
+                                            "event_time BIGINT",
+                                            "ts TIMESTAMP_LTZ(3)",
+                                            "WATERMARK FOR ts AS ts - INTERVAL 
'10' SECOND")
+                                    .producedValues(
+                                            Row.of("Vas", "login", 3L, 
Instant.ofEpochMilli(3000)),
+                                            Row.of("Vas", "click", 1L, 
Instant.ofEpochMilli(1000)))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(
+                                            "user_name STRING",
+                                            "payload STRING",
+                                            "event_time BIGINT")
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "click", 1L))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT user_name, payload, 
event_time "
+                                    + "FROM DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "on_time => DESCRIPTOR(ts))")
+                    .build();
+
+    public static final TableTestProgram EVENT_TIME_LATE_DROPPED =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-event-time-late-dropped",
+                            "a row at or below the watermark is dropped, even 
though its event "
+                                    + "time is earlier than the 
already-finalized candidate; a late "
+                                    + "first row for an unseen key is dropped 
without marking the "
+                                    + "key as seen")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(TIMED_EVENTS_SCHEMA)
+                                    .producedValues(
+                                            Row.of("Bob", "early", 
Instant.ofEpochMilli(1000)),
+                                            Row.of("Bob", "advance", 
Instant.ofEpochMilli(20000)),
+                                            Row.of("Bob", "late", 
Instant.ofEpochMilli(500)),
+                                            Row.of("Carol", "late", 
Instant.ofEpochMilli(500)),
+                                            Row.of(
+                                                    "Dave",
+                                                    "at-watermark",
+                                                    
Instant.ofEpochMilli(10000)),
+                                            Row.of("Dave", "on-time", 
Instant.ofEpochMilli(15000)),
+                                            Row.of("Carol", "on-time", 
Instant.ofEpochMilli(30000)))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema("user_name STRING", "action 
STRING")
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, "Bob", 
"early"),
+                                            Row.ofKind(RowKind.INSERT, "Dave", 
"on-time"),
+                                            Row.ofKind(RowKind.INSERT, 
"Carol", "on-time"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT user_name, action FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "on_time => DESCRIPTOR(ts))")
+                    .build();
+
+    public static final TableTestProgram UPDATING_INPUT =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-updating-input",
+                            "an updating input is deduplicated into an 
insert-only result: a -D "
+                                    + "before the key is seen is ignored, the 
first +I is emitted "
+                                    + "once and every later change (duplicate, 
-U, +U, -D) is "
+                                    + "swallowed")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .addOption("changelog-mode", "I,UB,UA,D")
+                                    .producedValues(
+                                            Row.ofKind(RowKind.DELETE, "Vas", 
"logout"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"),
+                                            Row.ofKind(RowKind.UPDATE_BEFORE, 
"Vas", "login"),
+                                            Row.ofKind(RowKind.UPDATE_AFTER, 
"Vas", "click"),
+                                            Row.ofKind(RowKind.DELETE, "Vas", 
"click"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(Row.ofKind(RowKind.INSERT, 
"Vas", "login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram UNSEEN_RETRACTION_IGNORED =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-unseen-retraction-ignored",
+                            "a -U or -D for a key that has not been seen is 
ignored and does not "
+                                    + "mark the key as seen, so the next +I or 
+U for that key is "
+                                    + "emitted as an insert")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .addOption("changelog-mode", "I,UB,UA,D")
+                                    .producedValues(
+                                            Row.ofKind(RowKind.DELETE, "Vas", 
"logout"),
+                                            Row.ofKind(RowKind.UPDATE_BEFORE, 
"Bob", "login"),
+                                            Row.ofKind(RowKind.UPDATE_AFTER, 
"Bob", "click"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema(USER_EVENTS_SCHEMA)
+                                    .consumedValues(
+                                            Row.ofKind(RowKind.INSERT, "Bob", 
"click"),
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login"))
+                                    .build())
+                    .runSql(
+                            "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name)")
+                    .build();
+
+    public static final TableTestProgram UPDATING_EVENT_TIME_FAILS =
+            TableTestProgram.of(
+                            "deduplicate-keep-first-updating-event-time-fails",
+                            "event-time mode (on_time) is rejected for 
updating input, because a "
+                                    + "watermark asserts no earlier record 
will arrive while an "
+                                    + "update can invalidate that")
+                    .setupTableSource(
+                            SourceTestStep.newBuilder("user_events")
+                                    .addSchema(TIMED_EVENTS_SCHEMA)
+                                    .addOption("changelog-mode", "I,UB,UA,D")
+                                    .producedValues(
+                                            Row.ofKind(RowKind.INSERT, "Vas", 
"login", null))
+                                    .build())
+                    .setupTableSink(
+                            SinkTestStep.newBuilder("sink")
+                                    .addSchema("user_name STRING", "action 
STRING")
+                                    .consumedValues(new Row[0])
+                                    .build())
+                    .runFailingSql(
+                            "INSERT INTO sink SELECT user_name, action FROM 
DEDUPLICATE_KEEP_FIRST("
+                                    + "input => TABLE user_events PARTITION BY 
user_name, "
+                                    + "on_time => DESCRIPTOR(ts))",
+                            ValidationException.class,
+                            "not supported for PTFs that consume or produce 
updates")
+                    .build();
+
+    public static final TableTestProgram NEGATIVE_TTL_FAILS =
+            invalidArgumentProgram(
+                    "deduplicate-keep-first-negative-ttl-fails",
+                    "a negative state_ttl is rejected at planning time",
+                    "state_ttl => INTERVAL '-1' SECOND",
+                    "The 'state_ttl' argument must not be negative");
+
+    public static final TableTestProgram NON_LITERAL_TTL_FAILS =
+            invalidArgumentProgram(
+                    "deduplicate-keep-first-non-literal-ttl-fails",
+                    "a state_ttl that is not a literal is rejected at planning 
time",
+                    "state_ttl => INTERVAL '1' SECOND * 2",
+                    "The 'state_ttl' argument must be a constant INTERVAL 
literal.");
+
+    public static final TableTestProgram NON_LITERAL_RESET_FAILS =
+            invalidArgumentProgram(
+                    "deduplicate-keep-first-non-literal-reset-fails",
+                    "a reset_ttl_on_duplicate that is not a literal is 
rejected at planning time",
+                    "reset_ttl_on_duplicate => 1 = 1",
+                    "The 'reset_ttl_on_duplicate' argument must be a constant 
BOOLEAN literal.");
+
+    private static TableTestProgram invalidArgumentProgram(
+            final String id, final String description, final String argument, 
final String error) {
+        return TableTestProgram.of(id, description)
+                .setupTableSource(
+                        SourceTestStep.newBuilder("user_events")
+                                .addSchema(USER_EVENTS_SCHEMA)
+                                .producedValues(Row.of("Vas", "login"))
+                                .build())
+                .setupTableSink(
+                        SinkTestStep.newBuilder("sink")
+                                .addSchema(USER_EVENTS_SCHEMA)
+                                .consumedValues(new Row[0])
+                                .build())
+                .runFailingSql(
+                        "INSERT INTO sink SELECT * FROM 
DEDUPLICATE_KEEP_FIRST("
+                                + "input => TABLE user_events PARTITION BY 
user_name, "
+                                + argument
+                                + ")",
+                        ValidationException.class,
+                        error)
+                .build();
+    }
+}
diff --git 
a/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/plan/deduplicate-keep-first-event-time-pending-restore.json
 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/plan/deduplicate-keep-first-event-time-pending-restore.json
new file mode 100644
index 00000000000..0f0841b7164
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/plan/deduplicate-keep-first-event-time-pending-restore.json
@@ -0,0 +1,352 @@
+{
+  "flinkVersion" : "2.4",
+  "nodes" : [ {
+    "id" : 5,
+    "type" : "stream-exec-table-source-scan_2",
+    "scanTableSource" : {
+      "table" : {
+        "identifier" : "`default_catalog`.`default_database`.`user_events`",
+        "resolvedTable" : {
+          "schema" : {
+            "columns" : [ {
+              "name" : "user_name",
+              "dataType" : "VARCHAR(2147483647)"
+            }, {
+              "name" : "action",
+              "dataType" : "VARCHAR(2147483647)"
+            }, {
+              "name" : "ts",
+              "dataType" : {
+                "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+                "precision" : 3,
+                "kind" : "ROWTIME"
+              }
+            } ],
+            "watermarkSpecs" : [ {
+              "rowtimeAttribute" : "ts",
+              "expression" : {
+                "rexNode" : {
+                  "kind" : "CALL",
+                  "syntax" : "BINARY",
+                  "internalName" : "$-$1",
+                  "operands" : [ {
+                    "kind" : "INPUT_REF",
+                    "inputIndex" : 2,
+                    "type" : "TIMESTAMP(3) WITH LOCAL TIME ZONE"
+                  }, {
+                    "kind" : "LITERAL",
+                    "value" : "1",
+                    "type" : "INTERVAL SECOND(6) NOT NULL"
+                  } ],
+                  "type" : "TIMESTAMP(3) WITH LOCAL TIME ZONE"
+                },
+                "serializableString" : "`ts` - INTERVAL '0.001' SECOND"
+              }
+            } ]
+          }
+        }
+      },
+      "abilities" : [ {
+        "type" : "WatermarkPushDown",
+        "watermarkExpr" : {
+          "kind" : "CALL",
+          "syntax" : "BINARY",
+          "internalName" : "$-$1",
+          "operands" : [ {
+            "kind" : "INPUT_REF",
+            "inputIndex" : 2,
+            "type" : "TIMESTAMP(3) WITH LOCAL TIME ZONE"
+          }, {
+            "kind" : "LITERAL",
+            "value" : "1",
+            "type" : "INTERVAL SECOND(6) NOT NULL"
+          } ],
+          "type" : "TIMESTAMP(3) WITH LOCAL TIME ZONE"
+        },
+        "rowtimeExpr" : {
+          "kind" : "INPUT_REF",
+          "inputIndex" : 2,
+          "type" : "TIMESTAMP(3) WITH LOCAL TIME ZONE"
+        },
+        "idleTimeoutMillis" : -1,
+        "producedType" : {
+          "type" : "ROW",
+          "nullable" : false,
+          "fields" : [ {
+            "name" : "user_name",
+            "fieldType" : "VARCHAR(2147483647)"
+          }, {
+            "name" : "action",
+            "fieldType" : "VARCHAR(2147483647)"
+          }, {
+            "name" : "ts",
+            "fieldType" : {
+              "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+              "precision" : 3,
+              "kind" : "ROWTIME"
+            }
+          } ]
+        },
+        "watermarkParams" : {
+          "emitStrategy" : "ON_EVENT",
+          "alignGroupName" : null,
+          "alignMaxDrift" : "PT0S",
+          "alignUpdateInterval" : "PT1S",
+          "sourceIdleTimeout" : -1
+        }
+      } ]
+    },
+    "outputType" : {
+      "type" : "ROW",
+      "fields" : [ {
+        "name" : "user_name",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "action",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "ts",
+        "fieldType" : {
+          "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+          "precision" : 3,
+          "kind" : "ROWTIME"
+        }
+      } ]
+    },
+    "description" : "TableSourceScan(table=[[default_catalog, 
default_database, user_events, watermark=[-(ts, 1:INTERVAL SECOND)], 
watermarkEmitStrategy=[on-event]]], fields=[user_name, action, ts])"
+  }, {
+    "id" : 6,
+    "type" : "stream-exec-exchange_1",
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "HASH",
+        "keys" : [ 0 ]
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : {
+      "type" : "ROW",
+      "fields" : [ {
+        "name" : "user_name",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "action",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "ts",
+        "fieldType" : {
+          "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+          "precision" : 3,
+          "kind" : "ROWTIME"
+        }
+      } ]
+    },
+    "description" : "Exchange(distribution=[hash[user_name]])"
+  }, {
+    "id" : 7,
+    "type" : "stream-exec-process-table-function_1",
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "UNKNOWN"
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : {
+      "type" : "ROW",
+      "fields" : [ {
+        "name" : "user_name",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "action",
+        "fieldType" : "VARCHAR(2147483647)"
+      }, {
+        "name" : "ts",
+        "fieldType" : {
+          "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+          "precision" : 3,
+          "kind" : "ROWTIME"
+        }
+      }, {
+        "name" : "rowtime",
+        "fieldType" : {
+          "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+          "nullable" : false,
+          "precision" : 3,
+          "kind" : "ROWTIME"
+        }
+      } ]
+    },
+    "description" : 
"ProcessTableFunction(invocation=[DEDUPLICATE_KEEP_FIRST(TABLE(#0) PARTITION 
BY($0), DEFAULT(), DEFAULT(), DESCRIPTOR(_UTF-16LE'ts'), DEFAULT())], 
uid=[DEDUPLICATE_KEEP_FIRST], select=[user_name,action,ts,rowtime], 
rowType=[RecordType(VARCHAR(2147483647) user_name, VARCHAR(2147483647) action, 
TIMESTAMP_LTZ(3) *ROWTIME* ts, TIMESTAMP_LTZ(3) *ROWTIME* rowtime)])",
+    "uid" : "DEDUPLICATE_KEEP_FIRST",
+    "functionCall" : {
+      "kind" : "CALL",
+      "internalName" : "$DEDUPLICATE_KEEP_FIRST$1",
+      "operands" : [ {
+        "kind" : "TABLE_ARG_CALL",
+        "inputIndex" : 0,
+        "partitionKeys" : [ 0 ],
+        "type" : {
+          "type" : "ROW",
+          "nullable" : false,
+          "fields" : [ {
+            "name" : "user_name",
+            "fieldType" : "VARCHAR(2147483647)"
+          }, {
+            "name" : "action",
+            "fieldType" : "VARCHAR(2147483647)"
+          }, {
+            "name" : "ts",
+            "fieldType" : {
+              "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+              "precision" : 3,
+              "kind" : "ROWTIME"
+            }
+          } ]
+        }
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "INTERVAL SECOND(6)"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "BOOLEAN"
+      }, {
+        "kind" : "CALL",
+        "internalName" : "$DESCRIPTOR$1",
+        "operands" : [ {
+          "kind" : "LITERAL",
+          "value" : "ts",
+          "type" : "CHAR(2) NOT NULL"
+        } ],
+        "type" : "DESCRIPTOR NOT NULL"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "VARCHAR(2147483647)"
+      } ],
+      "type" : {
+        "type" : "ROW",
+        "nullable" : false,
+        "fields" : [ {
+          "name" : "user_name",
+          "fieldType" : "VARCHAR(2147483647)"
+        }, {
+          "name" : "action",
+          "fieldType" : "VARCHAR(2147483647)"
+        }, {
+          "name" : "ts",
+          "fieldType" : {
+            "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+            "precision" : 3,
+            "kind" : "ROWTIME"
+          }
+        }, {
+          "name" : "rowtime",
+          "fieldType" : {
+            "type" : "TIMESTAMP_WITH_LOCAL_TIME_ZONE",
+            "nullable" : false,
+            "precision" : 3,
+            "kind" : "ROWTIME"
+          }
+        } ]
+      }
+    },
+    "inputChangelogModes" : [ [ "INSERT" ] ],
+    "outputChangelogMode" : [ "INSERT" ],
+    "inputUpsertKeys" : [ [ ] ]
+  }, {
+    "id" : 8,
+    "type" : "stream-exec-calc_1",
+    "projection" : [ {
+      "kind" : "INPUT_REF",
+      "inputIndex" : 0,
+      "type" : "VARCHAR(2147483647)"
+    }, {
+      "kind" : "INPUT_REF",
+      "inputIndex" : 1,
+      "type" : "VARCHAR(2147483647)"
+    } ],
+    "condition" : null,
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "UNKNOWN"
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : "Calc(select=[user_name, action])"
+  }, {
+    "id" : 9,
+    "type" : "stream-exec-sink_2",
+    "configuration" : {
+      "table.exec.sink.keyed-shuffle" : "AUTO",
+      "table.exec.sink.not-null-enforcer" : "ERROR",
+      "table.exec.sink.rowtime-inserter" : "ENABLED",
+      "table.exec.sink.type-length-enforcer" : "IGNORE",
+      "table.exec.sink.upsert-materialize" : "AUTO"
+    },
+    "dynamicTableSink" : {
+      "table" : {
+        "identifier" : "`default_catalog`.`default_database`.`sink`",
+        "resolvedTable" : {
+          "schema" : {
+            "columns" : [ {
+              "name" : "user_name",
+              "dataType" : "VARCHAR(2147483647)"
+            }, {
+              "name" : "action",
+              "dataType" : "VARCHAR(2147483647)"
+            } ]
+          }
+        }
+      }
+    },
+    "inputChangelogMode" : [ "INSERT" ],
+    "upsertMaterializeStrategy" : "ADAPTIVE",
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "UNKNOWN"
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : "Sink(table=[default_catalog.default_database.sink], 
fields=[user_name, action])"
+  } ],
+  "edges" : [ {
+    "source" : 5,
+    "target" : 6,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  }, {
+    "source" : 6,
+    "target" : 7,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  }, {
+    "source" : 7,
+    "target" : 8,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  }, {
+    "source" : 8,
+    "target" : 9,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  } ]
+}
\ No newline at end of file
diff --git 
a/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/savepoint/_metadata
 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/savepoint/_metadata
new file mode 100644
index 00000000000..37b4d901412
Binary files /dev/null and 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-event-time-pending-restore/savepoint/_metadata
 differ
diff --git 
a/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/plan/deduplicate-keep-first-keyed-restore.json
 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/plan/deduplicate-keep-first-keyed-restore.json
new file mode 100644
index 00000000000..2204a83fdc8
--- /dev/null
+++ 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/plan/deduplicate-keep-first-keyed-restore.json
@@ -0,0 +1,143 @@
+{
+  "flinkVersion" : "2.5",
+  "nodes" : [ {
+    "id" : 1,
+    "type" : "stream-exec-table-source-scan_2",
+    "scanTableSource" : {
+      "table" : {
+        "identifier" : "`default_catalog`.`default_database`.`user_events`",
+        "resolvedTable" : {
+          "schema" : {
+            "columns" : [ {
+              "name" : "user_name",
+              "dataType" : "VARCHAR(2147483647)"
+            }, {
+              "name" : "action",
+              "dataType" : "VARCHAR(2147483647)"
+            } ]
+          }
+        }
+      }
+    },
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : "TableSourceScan(table=[[default_catalog, 
default_database, user_events]], fields=[user_name, action])"
+  }, {
+    "id" : 2,
+    "type" : "stream-exec-exchange_1",
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "HASH",
+        "keys" : [ 0 ]
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : "Exchange(distribution=[hash[user_name]])"
+  }, {
+    "id" : 3,
+    "type" : "stream-exec-process-table-function_1",
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "UNKNOWN"
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : 
"ProcessTableFunction(invocation=[DEDUPLICATE_KEEP_FIRST(TABLE(#0) PARTITION 
BY($0), DEFAULT(), DEFAULT(), DEFAULT(), DEFAULT())], 
uid=[DEDUPLICATE_KEEP_FIRST], select=[user_name,action], 
rowType=[RecordType(VARCHAR(2147483647) user_name, VARCHAR(2147483647) 
action)])",
+    "uid" : "DEDUPLICATE_KEEP_FIRST",
+    "functionCall" : {
+      "kind" : "CALL",
+      "internalName" : "$DEDUPLICATE_KEEP_FIRST$1",
+      "operands" : [ {
+        "kind" : "TABLE_ARG_CALL",
+        "inputIndex" : 0,
+        "partitionKeys" : [ 0 ],
+        "type" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)> NOT NULL"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "INTERVAL SECOND(6)"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "BOOLEAN"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "DESCRIPTOR"
+      }, {
+        "kind" : "CALL",
+        "syntax" : "SPECIAL",
+        "internalName" : "$DEFAULT$1",
+        "type" : "VARCHAR(2147483647)"
+      } ],
+      "type" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)> NOT NULL"
+    },
+    "inputChangelogModes" : [ [ "INSERT" ] ],
+    "outputChangelogMode" : [ "INSERT" ],
+    "inputUpsertKeys" : [ [ ] ]
+  }, {
+    "id" : 4,
+    "type" : "stream-exec-sink_2",
+    "configuration" : {
+      "table.exec.sink.keyed-shuffle" : "AUTO",
+      "table.exec.sink.not-null-enforcer" : "ERROR",
+      "table.exec.sink.rowtime-inserter" : "ENABLED",
+      "table.exec.sink.type-length-enforcer" : "IGNORE",
+      "table.exec.sink.upsert-materialize" : "AUTO"
+    },
+    "dynamicTableSink" : {
+      "table" : {
+        "identifier" : "`default_catalog`.`default_database`.`sink`",
+        "resolvedTable" : {
+          "schema" : {
+            "columns" : [ {
+              "name" : "user_name",
+              "dataType" : "VARCHAR(2147483647)"
+            }, {
+              "name" : "action",
+              "dataType" : "VARCHAR(2147483647)"
+            } ]
+          }
+        }
+      }
+    },
+    "inputChangelogMode" : [ "INSERT" ],
+    "inputProperties" : [ {
+      "requiredDistribution" : {
+        "type" : "UNKNOWN"
+      },
+      "damBehavior" : "PIPELINED",
+      "priority" : 0
+    } ],
+    "outputType" : "ROW<`user_name` VARCHAR(2147483647), `action` 
VARCHAR(2147483647)>",
+    "description" : "Sink(table=[default_catalog.default_database.sink], 
fields=[user_name, action])"
+  } ],
+  "edges" : [ {
+    "source" : 1,
+    "target" : 2,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  }, {
+    "source" : 2,
+    "target" : 3,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  }, {
+    "source" : 3,
+    "target" : 4,
+    "shuffle" : {
+      "type" : "FORWARD"
+    },
+    "shuffleMode" : "PIPELINED"
+  } ]
+}
\ No newline at end of file
diff --git 
a/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/savepoint/_metadata
 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/savepoint/_metadata
new file mode 100644
index 00000000000..208bdc2d99f
Binary files /dev/null and 
b/flink-table/flink-table-planner/src/test/resources/restore-tests/stream-exec-process-table-function_1/deduplicate-keep-first-keyed-restore/savepoint/_metadata
 differ
diff --git 
a/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirst.java
 
b/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirst.java
new file mode 100644
index 00000000000..7744f43a67f
--- /dev/null
+++ 
b/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirst.java
@@ -0,0 +1,258 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.runtime.functions.ptf;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.table.api.DataTypes;
+import org.apache.flink.table.api.dataview.ValueView;
+import org.apache.flink.table.data.GenericRowData;
+import org.apache.flink.table.data.RowData;
+import org.apache.flink.table.data.utils.ProjectedRowData;
+import org.apache.flink.table.functions.BuiltInFunctionDefinitions;
+import org.apache.flink.table.functions.FunctionContext;
+import org.apache.flink.table.functions.TableSemantics;
+import org.apache.flink.table.functions.UserDefinedFunction;
+import org.apache.flink.table.runtime.functions.BuiltInSpecializedFunction;
+import org.apache.flink.table.runtime.typeutils.InternalSerializers;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.inference.StateTypeStrategy;
+import 
org.apache.flink.table.types.inference.strategies.ChangelogTypeStrategyUtils;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.RowType;
+import org.apache.flink.types.RowKind;
+
+import javax.annotation.Nullable;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import static 
org.apache.flink.table.types.inference.strategies.DeduplicateKeepFirstTypeStrategy.ARG_INPUT;
+import static 
org.apache.flink.table.types.inference.strategies.DeduplicateKeepFirstTypeStrategy.ARG_STATE_TTL;
+
+/**
+ * Implementation of the {@code DEDUPLICATE_KEEP_FIRST} process table function.
+ *
+ * <p>Specializes into {@link ProcessingTime} or {@link EventTime} depending 
on whether the input
+ * declares a time column, because only event time needs to buffer a candidate 
row.
+ */
+@Internal
+public class DeduplicateKeepFirst extends BuiltInSpecializedFunction {
+
+    public DeduplicateKeepFirst() {
+        super(BuiltInFunctionDefinitions.DEDUPLICATE_KEEP_FIRST);
+    }
+
+    @Override
+    public UserDefinedFunction specialize(final SpecializedContext context) {
+        return tableSemantics(context).timeColumn() == -1
+                ? new ProcessingTime(context)
+                : new EventTime(context);
+    }
+
+    private static TableSemantics tableSemantics(final SpecializedContext 
context) {
+        return context.getCallContext()
+                .getTableSemantics(ARG_INPUT)
+                .orElseThrow(() -> new IllegalStateException("Table argument 
expected."));
+    }
+
+    private static StateTypeStrategy seenState(final SpecializedContext 
context) {
+        return StateTypeStrategy.of(
+                callContext ->
+                        
Optional.of(ValueView.newValueViewDataType(DataTypes.BOOLEAN().notNull())),
+                context.getCallContext()
+                        .getArgumentValue(ARG_STATE_TTL, Duration.class)
+                        .orElse(null));
+    }
+
+    private static StateTypeStrategy candidateState(final SpecializedContext 
context) {
+        final TableSemantics tableSemantics = tableSemantics(context);
+        final List<DataTypes.Field> inputFields = 
DataType.getFields(tableSemantics.dataType());
+        final DataType payload =
+                DataTypes.ROW(
+                        Arrays.stream(
+                                        
ChangelogTypeStrategyUtils.computeOutputIndices(
+                                                tableSemantics))
+                                .mapToObj(inputFields::get)
+                                .toArray(DataTypes.Field[]::new));
+        final DataType candidate =
+                DataTypes.ROW(
+                        DataTypes.FIELD("payload", payload),
+                        DataTypes.FIELD("event_time", DataTypes.BIGINT()));
+        // The candidate buffer is cleared by its timer, not by retention; 
disable its TTL so a
+        // global table.exec.state.ttl cannot expire it before the timer fires.
+        return StateTypeStrategy.of(
+                callContext -> 
Optional.of(ValueView.newValueViewDataType(candidate)),
+                Duration.ZERO);
+    }
+
+    private abstract static class Base extends 
BuiltInProcessTableFunction<RowData> {
+
+        private static final long serialVersionUID = 1L;
+
+        protected final int[] outputIndices;
+
+        protected final RowType inputRowType;
+
+        Base(
+                final SpecializedContext context,
+                final LinkedHashMap<String, StateTypeStrategy> 
stateStrategies) {
+            super(BuiltInFunctionDefinitions.DEDUPLICATE_KEEP_FIRST, context, 
stateStrategies);
+            final TableSemantics tableSemantics = tableSemantics(context);
+            this.outputIndices = 
ChangelogTypeStrategyUtils.computeOutputIndices(tableSemantics);
+            this.inputRowType = (RowType) 
tableSemantics.dataType().getLogicalType();
+        }
+    }
+
+    /** Processing-time mode: emits the first arriving row per key. */
+    @Internal
+    public static class ProcessingTime extends Base {
+
+        private static final long serialVersionUID = 1L;
+
+        private transient ProjectedRowData projectedOutput;
+
+        public ProcessingTime(final SpecializedContext context) {
+            super(context, internalState(Map.entry("seen", 
seenState(context))));
+        }
+
+        @Override
+        public void open(final FunctionContext context) throws Exception {
+            super.open(context);
+            projectedOutput = ProjectedRowData.from(outputIndices);
+        }
+
+        public void eval(
+                final Context ctx,
+                final ValueView<Boolean> seen,
+                final RowData input,
+                @Nullable final Long stateTtl,
+                @Nullable final Boolean resetTtlOnDuplicate)
+                throws Exception {
+            // stateTtl is applied as the state's TTL at planning time.
+            final RowKind kind = input.getRowKind();
+            if (kind == RowKind.UPDATE_BEFORE || kind == RowKind.DELETE) {
+                return;
+            }
+
+            if (seen.getValue() == null) {
+                projectedOutput.replaceRow(input);
+                projectedOutput.setRowKind(RowKind.INSERT);
+                collect(projectedOutput);
+                seen.setValue(true);
+            } else if (resetTtlOnDuplicate == null || resetTtlOnDuplicate) {
+                seen.setValue(true);
+            }
+        }
+    }
+
+    /** Event-time mode: emits the row with the earliest event time per key. */
+    @Internal
+    public static class EventTime extends Base {
+
+        private static final long serialVersionUID = 1L;
+
+        private static final int CANDIDATE_PAYLOAD = 0;
+
+        private static final int CANDIDATE_EVENT_TIME = 1;
+
+        private transient RowData.FieldGetter[] payloadGetters;
+
+        private transient TypeSerializer<Object>[] payloadSerializers;
+
+        public EventTime(final SpecializedContext context) {
+            super(
+                    context,
+                    internalState(
+                            Map.entry("seen", seenState(context)),
+                            Map.entry("candidate", candidateState(context))));
+        }
+
+        @Override
+        public void open(final FunctionContext context) throws Exception {
+            super.open(context);
+            payloadGetters = new RowData.FieldGetter[outputIndices.length];
+            payloadSerializers = new TypeSerializer[outputIndices.length];
+            for (int i = 0; i < outputIndices.length; i++) {
+                final LogicalType payloadType = 
inputRowType.getTypeAt(outputIndices[i]);
+                payloadGetters[i] = RowData.createFieldGetter(payloadType, 
outputIndices[i]);
+                payloadSerializers[i] = 
InternalSerializers.create(payloadType);
+            }
+        }
+
+        public void eval(
+                final Context ctx,
+                final ValueView<Boolean> seen,
+                final ValueView<RowData> candidate,
+                final RowData input,
+                @Nullable final Long stateTtl,
+                @Nullable final Boolean resetTtlOnDuplicate)
+                throws Exception {
+            final TimeContext<Long> context = ctx.timeContext(Long.class);
+            final Long rowtime = context.time();
+            final Long watermark = context.tableWatermark();
+            if (watermark != null && rowtime <= watermark) {
+                return;
+            }
+
+            if (seen.getValue() == null) {
+                final RowData currLowest = candidate.getValue();
+                final Long currentLowestEventTime =
+                        currLowest == null ? null : 
currLowest.getLong(CANDIDATE_EVENT_TIME);
+                if (currentLowestEventTime == null || rowtime < 
currentLowestEventTime) {
+                    if (currentLowestEventTime != null) {
+                        context.clearTimer(currentLowestEventTime);
+                    }
+                    // object reuse may overwrite the input's memory before 
the timer fires
+                    candidate.setValue(materializeCandidate(input, rowtime));
+                    context.registerOnTime(rowtime);
+                }
+            } else if (resetTtlOnDuplicate == null || resetTtlOnDuplicate) {
+                seen.setValue(true);
+            }
+        }
+
+        public void onTimer(
+                final OnTimerContext ctx,
+                final ValueView<Boolean> seen,
+                final ValueView<RowData> candidate)
+                throws Exception {
+            final RowData currLowest = candidate.getValue();
+            if (currLowest == null) {
+                return;
+            }
+            collect(currLowest.getRow(CANDIDATE_PAYLOAD, 
outputIndices.length));
+            candidate.clear();
+            seen.setValue(true);
+        }
+
+        private GenericRowData materializeCandidate(final RowData input, final 
long rowtime) {
+            final GenericRowData payload = new 
GenericRowData(outputIndices.length);
+            for (int i = 0; i < outputIndices.length; i++) {
+                final Object field = payloadGetters[i].getFieldOrNull(input);
+                payload.setField(i, field == null ? null : 
payloadSerializers[i].copy(field));
+            }
+            return GenericRowData.of(payload, rowtime);
+        }
+    }
+}
diff --git 
a/flink-table/flink-table-runtime/src/test/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirstTest.java
 
b/flink-table/flink-table-runtime/src/test/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirstTest.java
new file mode 100644
index 00000000000..8d82d969980
--- /dev/null
+++ 
b/flink-table/flink-table-runtime/src/test/java/org/apache/flink/table/runtime/functions/ptf/DeduplicateKeepFirstTest.java
@@ -0,0 +1,174 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.runtime.functions.ptf;
+
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.ReadableConfig;
+import org.apache.flink.table.api.DataTypes;
+import org.apache.flink.table.api.dataview.ValueView;
+import org.apache.flink.table.expressions.Expression;
+import org.apache.flink.table.functions.BuiltInFunctionDefinition;
+import org.apache.flink.table.functions.BuiltInFunctionDefinitions;
+import 
org.apache.flink.table.functions.SpecializedFunction.ExpressionEvaluator;
+import org.apache.flink.table.functions.SpecializedFunction.SpecializedContext;
+import org.apache.flink.table.functions.UserDefinedFunction;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.inference.CallContext;
+import org.apache.flink.table.types.inference.StateTypeStrategy;
+import org.apache.flink.table.types.inference.utils.CallContextMock;
+import org.apache.flink.table.types.inference.utils.TableSemanticsMock;
+import org.apache.flink.table.types.utils.DataTypeFactoryMock;
+import org.apache.flink.table.types.utils.DataTypeUtils;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/** Tests for the state that each specialization of {@link 
DeduplicateKeepFirst} declares. */
+class DeduplicateKeepFirstTest {
+
+    private static final DataType INPUT_TYPE =
+            DataTypes.ROW(
+                    DataTypes.FIELD("user_name", DataTypes.STRING()),
+                    DataTypes.FIELD("action", DataTypes.STRING()),
+                    DataTypes.FIELD("ts", DataTypes.TIMESTAMP_LTZ(3)));
+
+    private static final DataType OUTPUT_TYPE =
+            DataTypes.ROW(
+                            DataTypes.FIELD("user_name", DataTypes.STRING()),
+                            DataTypes.FIELD("action", DataTypes.STRING()),
+                            DataTypes.FIELD("ts", DataTypes.TIMESTAMP_LTZ(3)))
+                    .notNull();
+
+    @Test
+    void testProcessingTimeDeclaresOnlySeenState() {
+        final CallContextMock callContext = callContext(-1, 
Duration.ofSeconds(5));
+        final UserDefinedFunction function = specialize(callContext);
+
+        
assertThat(function).isInstanceOf(DeduplicateKeepFirst.ProcessingTime.class);
+        final Map<String, StateTypeStrategy> state = stateStrategies(function);
+        assertThat(state).containsOnlyKeys("seen");
+        assertThat(state.get("seen").inferType(callContext))
+                
.contains(ValueView.newValueViewDataType(DataTypes.BOOLEAN().notNull()));
+        
assertThat(state.get("seen").getTimeToLive(callContext)).contains(Duration.ofSeconds(5));
+
+        final CallContextMock withoutTtl = callContext(-1, null);
+        
assertThat(stateStrategies(specialize(withoutTtl)).get("seen").getTimeToLive(withoutTtl))
+                .isEmpty();
+    }
+
+    @Test
+    void testEventTimeDeclaresSeenAndCandidateState() {
+        final CallContextMock callContext = callContext(2, 
Duration.ofSeconds(5));
+        final UserDefinedFunction function = specialize(callContext);
+
+        
assertThat(function).isInstanceOf(DeduplicateKeepFirst.EventTime.class);
+        final Map<String, StateTypeStrategy> state = stateStrategies(function);
+        assertThat(state.keySet()).containsExactly("seen", "candidate");
+        
assertThat(state.get("seen").getTimeToLive(callContext)).contains(Duration.ofSeconds(5));
+
+        final DataType candidate =
+                DataTypes.ROW(
+                        DataTypes.FIELD(
+                                "payload",
+                                DataTypes.ROW(
+                                        DataTypes.FIELD("action", 
DataTypes.STRING()),
+                                        DataTypes.FIELD("ts", 
DataTypes.TIMESTAMP_LTZ(3)))),
+                        DataTypes.FIELD("event_time", DataTypes.BIGINT()));
+        assertThat(state.get("candidate").inferType(callContext))
+                .contains(
+                        ValueView.newValueViewDataType(
+                                DataTypeUtils.toInternalDataType(candidate)));
+        // The timer, not retention, clears the candidate, so state_ttl must 
not apply to it.
+        
assertThat(state.get("candidate").getTimeToLive(callContext)).contains(Duration.ZERO);
+    }
+
+    private static Map<String, StateTypeStrategy> stateStrategies(
+            final UserDefinedFunction function) {
+        return function.getTypeInference(new 
DataTypeFactoryMock()).getStateTypeStrategies();
+    }
+
+    private static UserDefinedFunction specialize(final CallContext 
callContext) {
+        return new DeduplicateKeepFirst()
+                .specialize(
+                        new SpecializedContext() {
+                            @Override
+                            public CallContext getCallContext() {
+                                return callContext;
+                            }
+
+                            @Override
+                            public ReadableConfig getConfiguration() {
+                                return new Configuration();
+                            }
+
+                            @Override
+                            public ClassLoader getBuiltInClassLoader() {
+                                return 
DeduplicateKeepFirstTest.class.getClassLoader();
+                            }
+
+                            @Override
+                            public ExpressionEvaluator createEvaluator(
+                                    Expression expression,
+                                    DataType outputDataType,
+                                    DataTypes.Field... args) {
+                                throw new UnsupportedOperationException();
+                            }
+
+                            @Override
+                            public ExpressionEvaluator createEvaluator(
+                                    String sqlExpression,
+                                    DataType outputDataType,
+                                    DataTypes.Field... args) {
+                                throw new UnsupportedOperationException();
+                            }
+
+                            @Override
+                            public ExpressionEvaluator createEvaluator(
+                                    BuiltInFunctionDefinition function,
+                                    DataType outputDataType,
+                                    DataType... args) {
+                                throw new UnsupportedOperationException();
+                            }
+                        });
+    }
+
+    private static CallContextMock callContext(final int timeColumn, final 
Duration stateTtl) {
+        final CallContextMock callContext = new CallContextMock();
+        callContext.typeFactory = new DataTypeFactoryMock();
+        callContext.functionDefinition = 
BuiltInFunctionDefinitions.DEDUPLICATE_KEEP_FIRST;
+        callContext.argumentDataTypes =
+                List.of(INPUT_TYPE, DataTypes.INTERVAL(DataTypes.SECOND()), 
DataTypes.BOOLEAN());
+        callContext.argumentValues =
+                Arrays.asList(Optional.empty(), Optional.ofNullable(stateTtl), 
Optional.empty());
+        callContext.outputDataType = Optional.of(OUTPUT_TYPE);
+        callContext.tableSemantics =
+                Map.of(
+                        0,
+                        new TableSemanticsMock(
+                                INPUT_TYPE, new int[] {0}, new int[0], 
timeColumn, null));
+        return callContext;
+    }
+}

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