pnowojski commented on code in PR #27071: URL: https://github.com/apache/flink/pull/27071#discussion_r2402510234
########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/linked/LinkedMultiSetState.java: ########## @@ -0,0 +1,337 @@ +/* + * 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.orderedmultisetstate.linked; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.state.MapState; +import org.apache.flink.api.common.state.MapStateDescriptor; +import org.apache.flink.api.common.state.ValueState; +import org.apache.flink.api.common.state.ValueStateDescriptor; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.api.common.typeutils.base.LongSerializer; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.api.java.typeutils.runtime.TupleSerializer; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.generated.HashFunction; +import org.apache.flink.table.runtime.generated.RecordEqualiser; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetStateContext; +import org.apache.flink.table.runtime.orderedmultisetstate.TimeSelector; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Comparator; +import java.util.Iterator; +import java.util.List; +import java.util.Optional; +import java.util.function.Function; + +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.ALL_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.NOTHING_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_LAST_ADDED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_OTHER; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * This class implements an ordered multi-set state backend using Flink's state primitives. It + * maintains the insertion order of elements and supports operations such as adding, appending, and + * removing elements. The state is backed by Flink's `MapState` and `ValueState` to store and manage + * the relationships between rows and sequence numbers (SQNs). + * + * <p>Key features of this state implementation: + * + * <ul> + * <li>Maintains insertion order of elements using a doubly-linked list structure. + * <li>Supports both normal set semantics (replacing existing elements) and multi-set semantics + * (allowing duplicates). + * <li>Efficiently tracks the highest sequence number and links between elements for fast + * traversal and updates. + * <li>Provides methods to add, append, and remove elements with appropriate handling of state + * transitions. + * </ul> + * + * <p>Note: This implementation is marked as {@code @Internal} and is intended for internal use + * within Flink. It may be subject to changes in future versions. + * + * <p>Usage: + * + * <ul> + * <li>Use the {@link #add(RowData, long)} method to add an element, replacing any existing + * matching element. + * <li>Use the {@link #append(RowData, long)} method to append an element, allowing duplicates. + * <li>Use the {@link #remove(RowData)} method to remove an element, with detailed removal result + * types. + * </ul> + * + * @see OrderedMultiSetState + * @see org.apache.flink.api.common.state.MapState + * @see org.apache.flink.api.common.state.ValueState + */ +@Internal +public class LinkedMultiSetState implements OrderedMultiSetState<RowData> { + + // maps rows to SQNs (single SQN per RowData in case of upsert key; last SQN otherwise) + private final MapState<RowDataKey, Long> rowToSqnState; + // maps SQNs to Nodes, which comprise a doubly-linked list + private final MapState<Long, Node> sqnToNodeState; + // highest sequence number; also latest emitted downstream + private final ValueState<Tuple2<Long, Long>> highestSqnAndSizeState; + + private final RecordEqualiser keyEqualiser; + private final HashFunction keyHashFunction; + private final Function<RowData, RowData> keyExtractor; + private final TimeSelector timeSelector; + + private LinkedMultiSetState( + MapState<RowDataKey, Long> rowToSqnState, + MapState<Long, Node> sqnToNodeState, + ValueState<Tuple2<Long, Long>> highestSqnAndSizeState, + RecordEqualiser keyEqualiser, + HashFunction keyHashFunction, + Function<RowData, RowData> keyExtractor, + TimeSelector timeSelector) { + this.rowToSqnState = checkNotNull(rowToSqnState); + this.sqnToNodeState = checkNotNull(sqnToNodeState); + this.highestSqnAndSizeState = checkNotNull(highestSqnAndSizeState); + this.keyEqualiser = checkNotNull(keyEqualiser); + this.keyHashFunction = checkNotNull(keyHashFunction); + this.keyExtractor = keyExtractor; + this.timeSelector = timeSelector; + } + + public static OrderedMultiSetState<RowData> create( + OrderedMultiSetStateContext p, RuntimeContext ctx) { + + RecordEqualiser keyEqualiser = + p.generatedKeyEqualiser.newInstance(ctx.getUserCodeClassLoader()); + HashFunction keyHashFunction = + p.generatedKeyHashFunction.newInstance(ctx.getUserCodeClassLoader()); + + MapState<RowDataKey, Long> rowToSqnState = + ctx.getMapState( + new MapStateDescriptor<>( + "rowToSqnState", + new RowDataKeySerializer( + p.keySerializer, + keyEqualiser, + keyHashFunction, + p.generatedKeyEqualiser, + p.generatedKeyHashFunction), + LongSerializer.INSTANCE)); + MapState<Long, Node> sqnToNodeState = + ctx.getMapState( + new MapStateDescriptor<>( + "sqnToNodeState", + LongSerializer.INSTANCE, + new NodeSerializer(p.recordSerializer))); + + //noinspection rawtypes,unchecked + ValueState<Tuple2<Long, Long>> highestSqnState = + ctx.getState( + new ValueStateDescriptor<Tuple2<Long, Long>>( + "highestSqnState", + new TupleSerializer( + Tuple2.class, + new TypeSerializer[] { + LongSerializer.INSTANCE, LongSerializer.INSTANCE + }))); + + return new LinkedMultiSetState( + rowToSqnState, + sqnToNodeState, + highestSqnState, + keyEqualiser, + keyHashFunction, + p.keyExtractor, + p.config.getTimeSelector()); + } + + /** + * Add row, replacing any matching existing ones. + * + * @return RowKind.UPDATE_AFTER if an existing row was replaced; INSERT otherwise + */ + @Override + public SizeChangeInfo add(RowData row, long timestamp) throws Exception { + final RowDataKey key = toKey(row); + final Tuple2<Long, Long> highSqnAndSize = highestSqnAndSizeState.value(); + final Long highSqn = highSqnAndSize == null ? null : highSqnAndSize.f0; + final long oldSize = highSqnAndSize == null ? 0 : highSqnAndSize.f1; + final Long rowSqn = rowToSqnState.get(key); + final boolean append = rowSqn == null; + final boolean existed = highSqn != null; + + final Long oldSqn = append ? null : rowSqn; + final long newSqn = append ? (existed ? highSqn + 1 : 0) : oldSqn; + final long newSize = existed ? (append ? oldSize + 1 : oldSize) : 1; Review Comment: Does `!append` mean the newly added record overwritten previous record? Via upsert-key? Those three lines above are not very readable, maybe they are lacking some comments? Maybe it would be better to express it via ``` if (append) { if (existed) { // comment explaining oldSqn = ... newSqn = ... newSize = ... } else { // comment explaining ... } else { ... ``` or ``` if (append && existed) { // comment explaining oldSqn = ... newSqn = ... newSize = ... else if (...) { ... ``` ? ########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/linked/LinkedMultiSetState.java: ########## @@ -0,0 +1,337 @@ +/* + * 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.orderedmultisetstate.linked; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.state.MapState; +import org.apache.flink.api.common.state.MapStateDescriptor; +import org.apache.flink.api.common.state.ValueState; +import org.apache.flink.api.common.state.ValueStateDescriptor; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.api.common.typeutils.base.LongSerializer; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.api.java.typeutils.runtime.TupleSerializer; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.generated.HashFunction; +import org.apache.flink.table.runtime.generated.RecordEqualiser; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetStateContext; +import org.apache.flink.table.runtime.orderedmultisetstate.TimeSelector; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Comparator; +import java.util.Iterator; +import java.util.List; +import java.util.Optional; +import java.util.function.Function; + +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.ALL_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.NOTHING_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_LAST_ADDED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_OTHER; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * This class implements an ordered multi-set state backend using Flink's state primitives. It + * maintains the insertion order of elements and supports operations such as adding, appending, and + * removing elements. The state is backed by Flink's `MapState` and `ValueState` to store and manage + * the relationships between rows and sequence numbers (SQNs). + * + * <p>Key features of this state implementation: + * + * <ul> + * <li>Maintains insertion order of elements using a doubly-linked list structure. + * <li>Supports both normal set semantics (replacing existing elements) and multi-set semantics + * (allowing duplicates). + * <li>Efficiently tracks the highest sequence number and links between elements for fast + * traversal and updates. + * <li>Provides methods to add, append, and remove elements with appropriate handling of state + * transitions. + * </ul> + * + * <p>Note: This implementation is marked as {@code @Internal} and is intended for internal use + * within Flink. It may be subject to changes in future versions. + * + * <p>Usage: + * + * <ul> + * <li>Use the {@link #add(RowData, long)} method to add an element, replacing any existing + * matching element. + * <li>Use the {@link #append(RowData, long)} method to append an element, allowing duplicates. + * <li>Use the {@link #remove(RowData)} method to remove an element, with detailed removal result + * types. + * </ul> + * + * @see OrderedMultiSetState + * @see org.apache.flink.api.common.state.MapState + * @see org.apache.flink.api.common.state.ValueState + */ +@Internal +public class LinkedMultiSetState implements OrderedMultiSetState<RowData> { + + // maps rows to SQNs (single SQN per RowData in case of upsert key; last SQN otherwise) + private final MapState<RowDataKey, Long> rowToSqnState; + // maps SQNs to Nodes, which comprise a doubly-linked list + private final MapState<Long, Node> sqnToNodeState; + // highest sequence number; also latest emitted downstream + private final ValueState<Tuple2<Long, Long>> highestSqnAndSizeState; + + private final RecordEqualiser keyEqualiser; + private final HashFunction keyHashFunction; + private final Function<RowData, RowData> keyExtractor; + private final TimeSelector timeSelector; + + private LinkedMultiSetState( + MapState<RowDataKey, Long> rowToSqnState, + MapState<Long, Node> sqnToNodeState, + ValueState<Tuple2<Long, Long>> highestSqnAndSizeState, + RecordEqualiser keyEqualiser, + HashFunction keyHashFunction, + Function<RowData, RowData> keyExtractor, + TimeSelector timeSelector) { + this.rowToSqnState = checkNotNull(rowToSqnState); + this.sqnToNodeState = checkNotNull(sqnToNodeState); + this.highestSqnAndSizeState = checkNotNull(highestSqnAndSizeState); + this.keyEqualiser = checkNotNull(keyEqualiser); + this.keyHashFunction = checkNotNull(keyHashFunction); + this.keyExtractor = keyExtractor; + this.timeSelector = timeSelector; + } + + public static OrderedMultiSetState<RowData> create( + OrderedMultiSetStateContext p, RuntimeContext ctx) { + + RecordEqualiser keyEqualiser = + p.generatedKeyEqualiser.newInstance(ctx.getUserCodeClassLoader()); + HashFunction keyHashFunction = + p.generatedKeyHashFunction.newInstance(ctx.getUserCodeClassLoader()); + + MapState<RowDataKey, Long> rowToSqnState = + ctx.getMapState( + new MapStateDescriptor<>( + "rowToSqnState", + new RowDataKeySerializer( + p.keySerializer, + keyEqualiser, + keyHashFunction, + p.generatedKeyEqualiser, + p.generatedKeyHashFunction), + LongSerializer.INSTANCE)); + MapState<Long, Node> sqnToNodeState = + ctx.getMapState( + new MapStateDescriptor<>( + "sqnToNodeState", + LongSerializer.INSTANCE, + new NodeSerializer(p.recordSerializer))); + + //noinspection rawtypes,unchecked + ValueState<Tuple2<Long, Long>> highestSqnState = + ctx.getState( + new ValueStateDescriptor<Tuple2<Long, Long>>( + "highestSqnState", + new TupleSerializer( + Tuple2.class, + new TypeSerializer[] { + LongSerializer.INSTANCE, LongSerializer.INSTANCE + }))); + + return new LinkedMultiSetState( + rowToSqnState, + sqnToNodeState, + highestSqnState, + keyEqualiser, + keyHashFunction, + p.keyExtractor, + p.config.getTimeSelector()); + } + + /** + * Add row, replacing any matching existing ones. + * + * @return RowKind.UPDATE_AFTER if an existing row was replaced; INSERT otherwise Review Comment: outdated doc? ########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/linked/LinkedMultiSetState.java: ########## @@ -0,0 +1,337 @@ +/* + * 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.orderedmultisetstate.linked; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.state.MapState; +import org.apache.flink.api.common.state.MapStateDescriptor; +import org.apache.flink.api.common.state.ValueState; +import org.apache.flink.api.common.state.ValueStateDescriptor; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.api.common.typeutils.base.LongSerializer; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.api.java.typeutils.runtime.TupleSerializer; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.generated.HashFunction; +import org.apache.flink.table.runtime.generated.RecordEqualiser; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetStateContext; +import org.apache.flink.table.runtime.orderedmultisetstate.TimeSelector; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Comparator; +import java.util.Iterator; +import java.util.List; +import java.util.Optional; +import java.util.function.Function; + +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.ALL_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.NOTHING_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_LAST_ADDED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_OTHER; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * This class implements an ordered multi-set state backend using Flink's state primitives. It + * maintains the insertion order of elements and supports operations such as adding, appending, and + * removing elements. The state is backed by Flink's `MapState` and `ValueState` to store and manage + * the relationships between rows and sequence numbers (SQNs). + * + * <p>Key features of this state implementation: + * + * <ul> + * <li>Maintains insertion order of elements using a doubly-linked list structure. + * <li>Supports both normal set semantics (replacing existing elements) and multi-set semantics + * (allowing duplicates). + * <li>Efficiently tracks the highest sequence number and links between elements for fast + * traversal and updates. + * <li>Provides methods to add, append, and remove elements with appropriate handling of state + * transitions. + * </ul> + * + * <p>Note: This implementation is marked as {@code @Internal} and is intended for internal use + * within Flink. It may be subject to changes in future versions. + * + * <p>Usage: + * + * <ul> + * <li>Use the {@link #add(RowData, long)} method to add an element, replacing any existing + * matching element. + * <li>Use the {@link #append(RowData, long)} method to append an element, allowing duplicates. + * <li>Use the {@link #remove(RowData)} method to remove an element, with detailed removal result + * types. + * </ul> + * + * @see OrderedMultiSetState + * @see org.apache.flink.api.common.state.MapState + * @see org.apache.flink.api.common.state.ValueState + */ +@Internal +public class LinkedMultiSetState implements OrderedMultiSetState<RowData> { Review Comment: I think we should have test coverage for this quite complex class. Ditto for `Value` and `Adaptive` versions, so probably one test suite to be executed on different implementations with adaptive configured in a couple of different ways? Plus some dedicated tests for switchover in `Adaptive` version? ########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/OrderedMultiSetState.java: ########## @@ -0,0 +1,173 @@ +/* + * 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.orderedmultisetstate; + +import org.apache.flink.annotation.Experimental; +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.orderedmultisetstate.linked.LinkedMultiSetState; + +import java.io.IOException; +import java.util.Iterator; +import java.util.Optional; + +/** + * This class represents an interface for managing an ordered multi-set state in Apache Flink. It + * provides methods to add, append, and remove elements while maintaining insertion order. + * + * <p>The state supports two types of semantics for adding elements: + * + * <ul> + * <li><b>Normal Set Semantics:</b> Replaces an existing matching element with the new one. + * <li><b>Multi-Set Semantics:</b> Appends the new element, allowing duplicates. + * </ul> + * + * <p>Removal operations are supported with different result types, indicating the outcome of the + * removal process, such as whether all elements were removed, the last added element was removed, + * or no elements were removed. + * + * @param <T> The type of elements stored in the state. + */ +@Internal +@Experimental +public interface OrderedMultiSetState<T> { + + /** + * Add the given element using a normal (non-multi) set semantics: if a matching element exists + * already, replace it (the timestamp is updated). + */ + SizeChangeInfo add(T element, long timestamp) throws Exception; + + /** Add the given element using a multi-set semantics, i.e. append. */ + SizeChangeInfo append(T element, long timestamp) throws Exception; Review Comment: Why do we need both? 🤔 ########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/OrderedMultiSetState.java: ########## @@ -0,0 +1,173 @@ +/* + * 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.orderedmultisetstate; + +import org.apache.flink.annotation.Experimental; +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.orderedmultisetstate.linked.LinkedMultiSetState; + +import java.io.IOException; +import java.util.Iterator; +import java.util.Optional; + +/** + * This class represents an interface for managing an ordered multi-set state in Apache Flink. It + * provides methods to add, append, and remove elements while maintaining insertion order. + * + * <p>The state supports two types of semantics for adding elements: + * + * <ul> + * <li><b>Normal Set Semantics:</b> Replaces an existing matching element with the new one. + * <li><b>Multi-Set Semantics:</b> Appends the new element, allowing duplicates. + * </ul> + * + * <p>Removal operations are supported with different result types, indicating the outcome of the + * removal process, such as whether all elements were removed, the last added element was removed, + * or no elements were removed. + * + * @param <T> The type of elements stored in the state. + */ +@Internal +@Experimental +public interface OrderedMultiSetState<T> { Review Comment: Maybe this should be actually named `SequencedMultiSetState`? Take a look at [SequencedSet](https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/util/SequencedSet.html) and [SequencedCollection](https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/util/SequencedCollection.html)? ########## flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/orderedmultisetstate/linked/LinkedMultiSetState.java: ########## @@ -0,0 +1,337 @@ +/* + * 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.orderedmultisetstate.linked; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.state.MapState; +import org.apache.flink.api.common.state.MapStateDescriptor; +import org.apache.flink.api.common.state.ValueState; +import org.apache.flink.api.common.state.ValueStateDescriptor; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.api.common.typeutils.base.LongSerializer; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.api.java.typeutils.runtime.TupleSerializer; +import org.apache.flink.table.data.RowData; +import org.apache.flink.table.runtime.generated.HashFunction; +import org.apache.flink.table.runtime.generated.RecordEqualiser; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState; +import org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetStateContext; +import org.apache.flink.table.runtime.orderedmultisetstate.TimeSelector; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Comparator; +import java.util.Iterator; +import java.util.List; +import java.util.Optional; +import java.util.function.Function; + +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.ALL_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.NOTHING_REMOVED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_LAST_ADDED; +import static org.apache.flink.table.runtime.orderedmultisetstate.OrderedMultiSetState.RemovalResultType.REMOVED_OTHER; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * This class implements an ordered multi-set state backend using Flink's state primitives. It + * maintains the insertion order of elements and supports operations such as adding, appending, and + * removing elements. The state is backed by Flink's `MapState` and `ValueState` to store and manage + * the relationships between rows and sequence numbers (SQNs). + * + * <p>Key features of this state implementation: + * + * <ul> + * <li>Maintains insertion order of elements using a doubly-linked list structure. + * <li>Supports both normal set semantics (replacing existing elements) and multi-set semantics + * (allowing duplicates). + * <li>Efficiently tracks the highest sequence number and links between elements for fast + * traversal and updates. + * <li>Provides methods to add, append, and remove elements with appropriate handling of state + * transitions. + * </ul> + * + * <p>Note: This implementation is marked as {@code @Internal} and is intended for internal use + * within Flink. It may be subject to changes in future versions. + * + * <p>Usage: + * + * <ul> + * <li>Use the {@link #add(RowData, long)} method to add an element, replacing any existing + * matching element. + * <li>Use the {@link #append(RowData, long)} method to append an element, allowing duplicates. + * <li>Use the {@link #remove(RowData)} method to remove an element, with detailed removal result + * types. + * </ul> + * + * @see OrderedMultiSetState + * @see org.apache.flink.api.common.state.MapState + * @see org.apache.flink.api.common.state.ValueState + */ +@Internal +public class LinkedMultiSetState implements OrderedMultiSetState<RowData> { + + // maps rows to SQNs (single SQN per RowData in case of upsert key; last SQN otherwise) + private final MapState<RowDataKey, Long> rowToSqnState; + // maps SQNs to Nodes, which comprise a doubly-linked list + private final MapState<Long, Node> sqnToNodeState; + // highest sequence number; also latest emitted downstream + private final ValueState<Tuple2<Long, Long>> highestSqnAndSizeState; + + private final RecordEqualiser keyEqualiser; + private final HashFunction keyHashFunction; + private final Function<RowData, RowData> keyExtractor; + private final TimeSelector timeSelector; + + private LinkedMultiSetState( + MapState<RowDataKey, Long> rowToSqnState, + MapState<Long, Node> sqnToNodeState, + ValueState<Tuple2<Long, Long>> highestSqnAndSizeState, + RecordEqualiser keyEqualiser, + HashFunction keyHashFunction, + Function<RowData, RowData> keyExtractor, + TimeSelector timeSelector) { + this.rowToSqnState = checkNotNull(rowToSqnState); + this.sqnToNodeState = checkNotNull(sqnToNodeState); + this.highestSqnAndSizeState = checkNotNull(highestSqnAndSizeState); + this.keyEqualiser = checkNotNull(keyEqualiser); + this.keyHashFunction = checkNotNull(keyHashFunction); + this.keyExtractor = keyExtractor; + this.timeSelector = timeSelector; + } + + public static OrderedMultiSetState<RowData> create( + OrderedMultiSetStateContext p, RuntimeContext ctx) { + + RecordEqualiser keyEqualiser = + p.generatedKeyEqualiser.newInstance(ctx.getUserCodeClassLoader()); + HashFunction keyHashFunction = + p.generatedKeyHashFunction.newInstance(ctx.getUserCodeClassLoader()); + + MapState<RowDataKey, Long> rowToSqnState = + ctx.getMapState( + new MapStateDescriptor<>( + "rowToSqnState", + new RowDataKeySerializer( + p.keySerializer, + keyEqualiser, + keyHashFunction, + p.generatedKeyEqualiser, + p.generatedKeyHashFunction), + LongSerializer.INSTANCE)); + MapState<Long, Node> sqnToNodeState = + ctx.getMapState( + new MapStateDescriptor<>( + "sqnToNodeState", + LongSerializer.INSTANCE, + new NodeSerializer(p.recordSerializer))); + + //noinspection rawtypes,unchecked + ValueState<Tuple2<Long, Long>> highestSqnState = + ctx.getState( + new ValueStateDescriptor<Tuple2<Long, Long>>( + "highestSqnState", + new TupleSerializer( + Tuple2.class, + new TypeSerializer[] { + LongSerializer.INSTANCE, LongSerializer.INSTANCE + }))); + + return new LinkedMultiSetState( + rowToSqnState, + sqnToNodeState, + highestSqnState, + keyEqualiser, + keyHashFunction, + p.keyExtractor, + p.config.getTimeSelector()); + } + + /** + * Add row, replacing any matching existing ones. + * + * @return RowKind.UPDATE_AFTER if an existing row was replaced; INSERT otherwise + */ + @Override + public SizeChangeInfo add(RowData row, long timestamp) throws Exception { + final RowDataKey key = toKey(row); + final Tuple2<Long, Long> highSqnAndSize = highestSqnAndSizeState.value(); + final Long highSqn = highSqnAndSize == null ? null : highSqnAndSize.f0; + final long oldSize = highSqnAndSize == null ? 0 : highSqnAndSize.f1; + final Long rowSqn = rowToSqnState.get(key); + final boolean append = rowSqn == null; + final boolean existed = highSqn != null; Review Comment: what does it mean `append` and `existed`? 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