gengliangwang commented on code in PR #55508: URL: https://github.com/apache/spark/pull/55508#discussion_r3140800698
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveChangelogTable.scala: ########## @@ -0,0 +1,311 @@ +/* + * 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.spark.sql.catalyst.analysis + +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.expressions.aggregate.{Count, Max, Min} +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.catalyst.streaming.StreamingRelationV2 +import org.apache.spark.sql.connector.catalog.{Changelog, ChangelogInfo} +import org.apache.spark.sql.errors.QueryCompilationErrors +import org.apache.spark.sql.execution.datasources.v2.{ChangelogTable, DataSourceV2Relation} +import org.apache.spark.sql.types.{IntegerType, StringType} + +/** + * Post-processes a resolved [[ChangelogTable]] read to apply CDC option semantics + * (carry-over removal, update detection) and to enforce supported option combinations. + * + * Fires after [[ResolveRelations]] has wrapped the connector's [[Changelog]] in a + * [[ChangelogTable]]. Both batch ([[DataSourceV2Relation]]) and streaming + * ([[StreamingRelationV2]]) reads are handled: + * - Batch: the requested post-processing passes are injected as logical operators on top + * of the relation. Carry-over removal and update detection are fused into a single + * pass over a (rowId, _commit_version)-partitioned Window: the Filter drops CoW + * carry-over pairs (same rowVersion on both sides) and the subsequent Project relabels + * real delete+insert pairs as update_preimage / update_postimage. + * - Streaming: post-processing is not yet supported. If the requested options would + * require any post-processing, the rule throws an explicit [[AnalysisException]] to + * prevent silent wrong results. Streams that don't require post-processing pass + * through unchanged. + * + * Net change computation (`deduplicationMode = netChanges`) is not yet implemented and + * is rejected up-front for both batch and streaming. + */ +object ResolveChangelogTable extends Rule[LogicalPlan] { + + /** + * Reserved (`__spark_cdc_*`) column names used internally by post-processing; + * connectors must not emit columns with these names. + */ + object HelperColumn { + final val DelCnt = "__spark_cdc_del_cnt" + final val InsCnt = "__spark_cdc_ins_cnt" + final val MinRv = "__spark_cdc_min_rv" + final val MaxRv = "__spark_cdc_max_rv" + final val RvCnt = "__spark_cdc_rv_cnt" + + val all: Set[String] = Set(DelCnt, InsCnt, MinRv, MaxRv, RvCnt) + } + + override def apply(plan: LogicalPlan): LogicalPlan = plan.resolveOperatorsUp { + case rel @ DataSourceV2Relation(table: ChangelogTable, _, _, _, _, _) if !table.resolved => + val changelog = table.changelog + val req = evaluateRequirements(changelog, table.changelogInfo) + + val resolvedRel = rel.copy(table = table.copy(resolved = true)) + var updatedRel: LogicalPlan = resolvedRel + if (req.requiresCarryOverRemoval || req.requiresUpdateDetection) { + updatedRel = addRowLevelPostProcessing( + resolvedRel, changelog, req.requiresCarryOverRemoval, req.requiresUpdateDetection) + } + if (req.requiresNetChanges) { + updatedRel = injectNetChangeComputation(updatedRel, changelog) + } + updatedRel + + case rel @ StreamingRelationV2(_, _, table: ChangelogTable, _, _, _, _, _, _) + if !table.resolved => + // Streaming CDC reads do not yet apply post-processing. Run the same option / + // capability validation as the batch path so silent wrong results are impossible: + // either no post-processing would be required (fall through, return raw stream), + // or we throw an explicit AnalysisException. + val changelog = table.changelog + val req = evaluateRequirements(changelog, table.changelogInfo) + if (req.needsAny) { + throw QueryCompilationErrors.cdcStreamingPostProcessingNotSupported(changelog.name()) + } + rel.copy(table = table.copy(resolved = true)) + } + + // --------------------------------------------------------------------------- + // Option validation & Requirement Computation + // --------------------------------------------------------------------------- + + /** + * Captures which post-processing passes a CDC query requires, derived from the + * user-provided [[ChangelogInfo]] options and the connector-declared [[Changelog]] + * capability flags. + */ + private case class PostProcessingRequirements( + requiresCarryOverRemoval: Boolean, + requiresUpdateDetection: Boolean, + requiresNetChanges: Boolean) { + def needsAny: Boolean = + requiresCarryOverRemoval || requiresUpdateDetection || requiresNetChanges + } + + /** + * Validates CDC option/capability combinations and computes which post-processing + * passes are required. Throws an [[org.apache.spark.sql.AnalysisException]] for + * unsupported or contradictory combinations (currently: `netChanges` deduplication, + * and `computeUpdates` with surfaced carry-overs but no carry-over removal). + */ + private def evaluateRequirements( + changelog: Changelog, + options: ChangelogInfo): PostProcessingRequirements = { + // Net change computation is not yet implemented. + if (options.deduplicationMode() == ChangelogInfo.DeduplicationMode.NET_CHANGES) { + throw QueryCompilationErrors.cdcNetChangesNotYetSupported(changelog.name()) + } + + val requiresCarryOverRemoval = + options.deduplicationMode() != ChangelogInfo.DeduplicationMode.NONE && + changelog.containsCarryoverRows() + val requiresUpdateDetection = + options.computeUpdates() && changelog.representsUpdateAsDeleteAndInsert() + val requiresNetChanges = + options.deduplicationMode() == ChangelogInfo.DeduplicationMode.NET_CHANGES && + changelog.containsIntermediateChanges() + + // If carry-overs are surfaced and update detection is enabled without carry-over + // removal, carry-overs would be falsely classified as updates, leading to wrong + // results. Hence we throw. + if (requiresUpdateDetection && + changelog.containsCarryoverRows() && + options.deduplicationMode() == ChangelogInfo.DeduplicationMode.NONE) { + throw QueryCompilationErrors.cdcUpdateDetectionRequiresCarryOverRemoval( + changelog.name()) + } + + PostProcessingRequirements( + requiresCarryOverRemoval, requiresUpdateDetection, requiresNetChanges) + } + + // --------------------------------------------------------------------------- + // Row Level Post Processing (Update Detection & Carry-over Removal) + // --------------------------------------------------------------------------- + + /** + * Adds row-level post-processing (carry-over removal and/or update detection) on top of + * the given plan. `counts` = per-partition delete and insert change_type row counts over + * `(rowId, _commit_version)`. `rv bounds` = per-partition min/max of `rowVersion`. + * Equal bounds signal a copy-on-write carry-over. + * - both active -> Window(counts + rv bounds) -> Filter -> Project(relabel) -> Drop helpers + * - carry-over only -> Window(counts + rv bounds) -> Filter -> Drop helpers + * - update only -> Window(counts only) -> Project(relabel) -> Drop helpers + * - neither -> not invoked (caller guards this case) + */ + private def addRowLevelPostProcessing( + plan: LogicalPlan, + cl: Changelog, + requiresCarryOverRemoval: Boolean, + requiresUpdateDetection: Boolean): LogicalPlan = { + // Row-version bounds in the Window are needed iff we filter carry-over pairs. + var modifiedPlan = addPostProcessingWindow(plan, cl, + includeRowVersionBounds = requiresCarryOverRemoval) + if (requiresCarryOverRemoval) modifiedPlan = addCarryOverPairFilter(modifiedPlan) + if (requiresUpdateDetection) modifiedPlan = addUpdateRelabelProjection(modifiedPlan) + removeHelperColumns(modifiedPlan) + } + + /** + * Adds a Window node partitioned by (rowId, _commit_version) that computes + * `_del_cnt` and `_ins_cnt` per partition, and, when `includeRowVersionBounds` + * is true, additionally `_min_rv` / `_max_rv` / `_rv_cnt` (min, max and non-null + * count of `Changelog.rowVersion()`). + * + * `_del_cnt` / `_ins_cnt` drive update detection (1 each -> relabel as + * update_preimage / update_postimage). `_min_rv` / `_max_rv` / `_rv_cnt` drive + * carry-over detection (within a delete+insert pair, `_rv_cnt = 2` AND equal + * bounds signal a CoW carry-over). + */ + private def addPostProcessingWindow( + plan: LogicalPlan, + cl: Changelog, + includeRowVersionBounds: Boolean): LogicalPlan = { + val changeTypeAttr = getAttribute(plan, "_change_type") + val rowIdExprs = V2ExpressionUtils.resolveRefs[NamedExpression](cl.rowId().toSeq, plan) + val commitVersionAttr = getAttribute(plan, "_commit_version") + val partitionByCols = rowIdExprs ++ Seq(commitVersionAttr) + val windowSpec = WindowSpecDefinition(partitionByCols, Nil, UnspecifiedFrame) + + val insertIf = If(EqualTo(changeTypeAttr, Literal("insert")), + Literal(1), Literal(null, IntegerType)) + val deleteIf = If(EqualTo(changeTypeAttr, Literal("delete")), + Literal(1), Literal(null, IntegerType)) Review Comment: The `_change_type` vocabulary (`"insert"` / `"delete"` here, `"update_preimage"` / `"update_postimage"` at L258–L259) is part of the connector contract documented at `Changelog.java:34–35`, but the rule references it as scattered bare-string literals. Two failure modes that aren't caught by anything: 1. A typo in the rule (e.g. `Literal("inset")`) compiles cleanly. `_ins_cnt` would silently be 0, no relabel ever fires, and update detection becomes a no-op — no test covers "the rule actually counts inserts as inserts" beyond the relabel happy path. 2. If the contract evolves (new value, casing change, alias), connectors and this rule drift independently — there's no shared symbol to grep for. This PR already extracted helper-column names into `HelperColumn` for the same reason. Suggest the same treatment for the change-type vocabulary — either as a public `ChangeType` object next to `HelperColumn` here, or (better, since it's a connector-facing contract) as `public static final` constants on the `Changelog` interface so connectors can use the same symbols when emitting rows. -- This is an automated message from the Apache Git Service. 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