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new 3f5129b8767 [FLINK-39784][table] Forbid SNAPSHOT outside a LATERAL
context (#28674)
3f5129b8767 is described below
commit 3f5129b87672fe91d4725d019b3e0b833c45ccc1
Author: Fabian Hueske <[email protected]>
AuthorDate: Wed Jul 15 10:15:19 2026 +0200
[FLINK-39784][table] Forbid SNAPSHOT outside a LATERAL context (#28674)
Adds ForbidSnapshotOutsideLateralRule, which rejects any SNAPSHOT scan
that survives the LATERAL SNAPSHOT rewrite with a clear message instead
of failing later in the generic PTF translation.
Generated-By: Claude Opus 4.8 (1M context)
---
.../logical/ForbidSnapshotOutsideLateralRule.java | 85 ++++++++++++++++++++++
.../planner/plan/rules/FlinkStreamRuleSets.scala | 3 +
.../plan/stream/sql/SnapshotTableFunctionTest.java | 12 +--
3 files changed, 95 insertions(+), 5 deletions(-)
diff --git
a/flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/ForbidSnapshotOutsideLateralRule.java
b/flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/ForbidSnapshotOutsideLateralRule.java
new file mode 100644
index 00000000000..95db7221528
--- /dev/null
+++
b/flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/ForbidSnapshotOutsideLateralRule.java
@@ -0,0 +1,85 @@
+/*
+ * 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.rules.logical;
+
+import org.apache.flink.table.api.ValidationException;
+import
org.apache.flink.table.planner.plan.nodes.logical.FlinkLogicalTableFunctionScan;
+import org.apache.flink.table.planner.plan.utils.LateralSnapshotJoinUtil;
+
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelRule;
+import org.apache.calcite.rex.RexCall;
+import org.immutables.value.Value;
+
+/**
+ * Rejects any {@link FlinkLogicalTableFunctionScan} that is still backed by
the built-in {@code
+ * SNAPSHOT} function, with a clear error message.
+ *
+ * <p>{@code SNAPSHOT} is a planner placeholder that is only valid as the
build side of a {@code
+ * LATERAL} join, where {@link LogicalJoinToLateralSnapshotJoinRule} rewrites
the surrounding join
+ * into a dedicated {@link
+ *
org.apache.flink.table.planner.plan.nodes.logical.FlinkLogicalLateralSnapshotJoin}
and removes
+ * the SNAPSHOT scan. This rule must therefore run <em>after</em> that rewrite
(see {@code
+ * FlinkStreamRuleSets.LOGICAL_REWRITE}).
+ */
[email protected]
+public class ForbidSnapshotOutsideLateralRule
+ extends
RelRule<ForbidSnapshotOutsideLateralRule.ForbidSnapshotOutsideLateralRuleConfig>
{
+
+ public static final ForbidSnapshotOutsideLateralRule INSTANCE =
+
ForbidSnapshotOutsideLateralRule.ForbidSnapshotOutsideLateralRuleConfig.DEFAULT
+ .toRule();
+
+ private
ForbidSnapshotOutsideLateralRule(ForbidSnapshotOutsideLateralRuleConfig config)
{
+ super(config);
+ }
+
+ @Override
+ public boolean matches(RelOptRuleCall call) {
+ final FlinkLogicalTableFunctionScan scan = call.rel(0);
+ return scan.getCall() instanceof RexCall
+ && LateralSnapshotJoinUtil.isSnapshotCall((RexCall)
scan.getCall());
+ }
+
+ @Override
+ public void onMatch(RelOptRuleCall call) {
+ throw new ValidationException(
+ "The SNAPSHOT function can only be used as the build side
(right-hand side) of a "
+ + "LATERAL join. It cannot be used as a standalone
table function or "
+ + "outside of a LATERAL context.");
+ }
+
+ /** Rule configuration. */
+ @Value.Immutable(singleton = false)
+ public interface ForbidSnapshotOutsideLateralRuleConfig extends
RelRule.Config {
+
+
ForbidSnapshotOutsideLateralRule.ForbidSnapshotOutsideLateralRuleConfig DEFAULT
=
+
ImmutableForbidSnapshotOutsideLateralRule.ForbidSnapshotOutsideLateralRuleConfig
+ .builder()
+ .build()
+ .withOperandSupplier(
+ b0 ->
b0.operand(FlinkLogicalTableFunctionScan.class).anyInputs())
+ .withDescription("ForbidSnapshotOutsideLateralRule");
+
+ @Override
+ default ForbidSnapshotOutsideLateralRule toRule() {
+ return new ForbidSnapshotOutsideLateralRule(this);
+ }
+ }
+}
diff --git
a/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/rules/FlinkStreamRuleSets.scala
b/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/rules/FlinkStreamRuleSets.scala
index 0617400e4ae..de637d07a24 100644
---
a/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/rules/FlinkStreamRuleSets.scala
+++
b/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/rules/FlinkStreamRuleSets.scala
@@ -406,6 +406,9 @@ object FlinkStreamRuleSets {
// Rewrites a join over a SNAPSHOT table function call into a dedicated
// FlinkLogicalLateralSnapshotJoin for the LATERAL SNAPSHOT operator.
LogicalJoinToLateralSnapshotJoinRule.INSTANCE,
+ // Rejects SNAPSHOT scans that survived the rewrite above, i.e. SNAPSHOT
calls used outside a
+ // LATERAL context. Must run after LogicalJoinToLateralSnapshotJoinRule.
+ ForbidSnapshotOutsideLateralRule.INSTANCE,
// Avoids accessing a field from the result (condition).
PythonCalcSplitRule.SPLIT_CONDITION_REX_FIELD,
// Avoids accessing a field from the result (projection).
diff --git
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/stream/sql/SnapshotTableFunctionTest.java
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/stream/sql/SnapshotTableFunctionTest.java
index 12511c4ae49..6d254b220b8 100644
---
a/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/stream/sql/SnapshotTableFunctionTest.java
+++
b/flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/stream/sql/SnapshotTableFunctionTest.java
@@ -19,6 +19,7 @@
package org.apache.flink.table.planner.plan.stream.sql;
import org.apache.flink.table.api.TableConfig;
+import org.apache.flink.table.api.ValidationException;
import org.apache.flink.table.planner.utils.TableTestBase;
import org.apache.flink.table.planner.utils.TableTestUtil;
@@ -153,13 +154,14 @@ public class SnapshotTableFunctionTest extends
TableTestBase {
@Test
void testFromContextRejectedOutsideLateral() {
- // SNAPSHOT used outside a LATERAL context is not rewritten by the
LATERAL SNAPSHOT rule and
- // reaches the regular PTF physical rule. Because SNAPSHOT disables
system arguments, that
- // rule rejects it. FLINK-39784 will replace this with a clearer
message
- // ("SNAPSHOT can only be used inside a LATERAL clause").
+ // SNAPSHOT used outside a LATERAL context is not rewritten by the
LATERAL SNAPSHOT rule.
+ // ForbidSnapshotOutsideLateralRule intercepts the surviving SNAPSHOT
scan and rejects it
+ // with a clear message before it reaches the generic PTF translation.
assertThatThrownBy(() -> util.verifyRelPlan("SELECT * FROM
SNAPSHOT(input => TABLE Rates)"))
.satisfies(
anyCauseMatches(
- "Disabling system arguments is not supported
for user-defined PTF."));
+ ValidationException.class,
+ "The SNAPSHOT function can only be used as the
build side "
+ + "(right-hand side) of a LATERAL
join"));
}
}
