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Pushdown dereference expressions in the query plan
Co-authored-by: qqibrow <[email protected]> Co-authored-by: Zhenxiao Luo <[email protected]>
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130
presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/DereferencePushdown.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| /* | ||
| * Licensed 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 io.prestosql.sql.planner.iterative.rule; | ||
|
|
||
| import com.google.common.collect.ImmutableList; | ||
| import io.prestosql.sql.planner.Symbol; | ||
| import io.prestosql.sql.tree.DefaultExpressionTraversalVisitor; | ||
| import io.prestosql.sql.tree.DereferenceExpression; | ||
| import io.prestosql.sql.tree.Expression; | ||
| import io.prestosql.sql.tree.LambdaExpression; | ||
| import io.prestosql.sql.tree.SymbolReference; | ||
|
|
||
| import java.util.Collection; | ||
| import java.util.List; | ||
| import java.util.Set; | ||
| import java.util.stream.Collectors; | ||
|
|
||
| import static com.google.common.base.Verify.verify; | ||
| import static com.google.common.collect.Iterables.getOnlyElement; | ||
| import static io.prestosql.sql.planner.SymbolsExtractor.extractAll; | ||
|
|
||
| /** | ||
| * Provides helper methods to push down dereferences in the query plan. | ||
| */ | ||
| class DereferencePushdown | ||
| { | ||
| private DereferencePushdown() {} | ||
|
|
||
| public static Set<DereferenceExpression> extractDereferences(Collection<Expression> expressions, boolean allowOverlap) | ||
| { | ||
| Set<Expression> symbolReferencesAndDereferences = expressions.stream() | ||
| .flatMap(expression -> getSymbolReferencesAndDereferences(expression).stream()) | ||
| .collect(Collectors.toSet()); | ||
|
|
||
| // Remove overlap if required | ||
| Set<Expression> candidateExpressions = symbolReferencesAndDereferences; | ||
| if (!allowOverlap) { | ||
| candidateExpressions = symbolReferencesAndDereferences.stream() | ||
| .filter(expression -> !prefixExists(expression, symbolReferencesAndDereferences)) | ||
| .collect(Collectors.toSet()); | ||
| } | ||
|
|
||
| // Retain dereference expressions | ||
| return candidateExpressions.stream() | ||
| .filter(DereferenceExpression.class::isInstance) | ||
| .map(DereferenceExpression.class::cast) | ||
| .collect(Collectors.toSet()); | ||
| } | ||
|
|
||
| public static boolean exclusiveDereferences(Set<Expression> projections) | ||
| { | ||
| return projections.stream() | ||
| .allMatch(expression -> expression instanceof SymbolReference || | ||
| (expression instanceof DereferenceExpression && | ||
| isDereferenceChain((DereferenceExpression) expression) && | ||
| !prefixExists(expression, projections))); | ||
| } | ||
|
|
||
| public static Symbol getBase(DereferenceExpression expression) | ||
| { | ||
| return getOnlyElement(extractAll(expression)); | ||
| } | ||
|
|
||
| /** | ||
| * Extract the sub-expressions of type {@link DereferenceExpression} or {@link SymbolReference} from the {@param expression} | ||
| * in a top-down manner. The expressions within the base of a valid {@link DereferenceExpression} sequence are not extracted. | ||
| */ | ||
| private static List<Expression> getSymbolReferencesAndDereferences(Expression expression) | ||
| { | ||
| ImmutableList.Builder<Expression> builder = ImmutableList.builder(); | ||
|
|
||
| new DefaultExpressionTraversalVisitor<ImmutableList.Builder<Expression>>() | ||
| { | ||
| @Override | ||
| protected Void visitDereferenceExpression(DereferenceExpression node, ImmutableList.Builder<Expression> context) | ||
| { | ||
| if (isDereferenceChain(node)) { | ||
| context.add(node); | ||
| } | ||
| return null; | ||
| } | ||
|
|
||
| @Override | ||
| protected Void visitSymbolReference(SymbolReference node, ImmutableList.Builder<Expression> context) | ||
| { | ||
| context.add(node); | ||
| return null; | ||
| } | ||
|
|
||
| @Override | ||
| protected Void visitLambdaExpression(LambdaExpression node, ImmutableList.Builder<Expression> context) | ||
| { | ||
| return null; | ||
| } | ||
| }.process(expression, builder); | ||
|
|
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| return builder.build(); | ||
| } | ||
|
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| private static boolean isDereferenceChain(DereferenceExpression expression) | ||
| { | ||
| return (expression.getBase() instanceof SymbolReference) || | ||
| ((expression.getBase() instanceof DereferenceExpression) && isDereferenceChain((DereferenceExpression) (expression.getBase()))); | ||
| } | ||
|
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| private static boolean prefixExists(Expression expression, Set<Expression> expressions) | ||
| { | ||
| Expression current = expression; | ||
| while (current instanceof DereferenceExpression) { | ||
| current = ((DereferenceExpression) current).getBase(); | ||
| if (expressions.contains(current)) { | ||
| return true; | ||
| } | ||
| } | ||
|
|
||
| verify(current instanceof SymbolReference); | ||
| return false; | ||
| } | ||
| } |
115 changes: 115 additions & 0 deletions
115
.../java/io/prestosql/sql/planner/iterative/rule/ExtractDereferencesFromFilterAboveScan.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| /* | ||
| * Licensed 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 io.prestosql.sql.planner.iterative.rule; | ||
|
|
||
| import com.google.common.collect.HashBiMap; | ||
| import com.google.common.collect.ImmutableList; | ||
| import io.prestosql.matching.Capture; | ||
| import io.prestosql.matching.Captures; | ||
| import io.prestosql.matching.Pattern; | ||
| import io.prestosql.sql.planner.TypeAnalyzer; | ||
| import io.prestosql.sql.planner.iterative.Rule; | ||
| import io.prestosql.sql.planner.plan.Assignments; | ||
| import io.prestosql.sql.planner.plan.FilterNode; | ||
| import io.prestosql.sql.planner.plan.PlanNode; | ||
| import io.prestosql.sql.planner.plan.ProjectNode; | ||
| import io.prestosql.sql.planner.plan.TableScanNode; | ||
| import io.prestosql.sql.tree.DereferenceExpression; | ||
| import io.prestosql.sql.tree.Expression; | ||
| import io.prestosql.sql.tree.SymbolReference; | ||
|
|
||
| import java.util.Map; | ||
| import java.util.Set; | ||
|
|
||
| import static com.google.common.collect.ImmutableMap.toImmutableMap; | ||
| import static io.prestosql.matching.Capture.newCapture; | ||
| import static io.prestosql.sql.planner.ExpressionNodeInliner.replaceExpression; | ||
| import static io.prestosql.sql.planner.iterative.rule.DereferencePushdown.extractDereferences; | ||
| import static io.prestosql.sql.planner.plan.Patterns.filter; | ||
| import static io.prestosql.sql.planner.plan.Patterns.source; | ||
| import static io.prestosql.sql.planner.plan.Patterns.tableScan; | ||
| import static java.util.Objects.requireNonNull; | ||
|
|
||
| /** | ||
| * Transforms: | ||
| * <pre> | ||
| * Filter(f1(A.x.y) = 1 AND f2(B.m) = 2 AND f3(A.x) = 6) | ||
| * Source(A, B, C) | ||
| * </pre> | ||
| * to: | ||
| * <pre> | ||
| * Project(A, B, C) | ||
| * Filter(f1(D) = 1 AND f2(E) = 2 AND f3(G) = 6) | ||
| * Project(A, B, C, D := A.x.y, E := B.m, G := A.x) | ||
| * Source(A, B, C) | ||
| * </pre> | ||
| * | ||
| * This optimizer extracts all dereference expressions from a filter node located above a table scan into a ProjectNode. | ||
| * | ||
| * Extracting dereferences from a filter (eg. FilterNode(a.x = 5)) can be suboptimal if full columns are being accessed up the | ||
| * plan tree (eg. a), because it can result in replicated shuffling of fields (eg. a.x). So it is safer to pushdown dereferences from | ||
| * Filter only when there's an explicit projection on top of the filter node (Ref PushDereferencesThroughFilter). | ||
| * | ||
| * In case of a FilterNode on top of TableScanNode, we want to push all dereferences into a new ProjectNode below, so that | ||
| * PushProjectionIntoTableScan optimizer can push those columns in the connector, and provide new column handles for the | ||
| * projected subcolumns. PushPredicateIntoTableScan optimizer can then push predicates on these subcolumns into the connector. | ||
| */ | ||
| public class ExtractDereferencesFromFilterAboveScan | ||
| implements Rule<FilterNode> | ||
| { | ||
| private static final Capture<TableScanNode> CHILD = newCapture(); | ||
| private final TypeAnalyzer typeAnalyzer; | ||
|
|
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| public ExtractDereferencesFromFilterAboveScan(TypeAnalyzer typeAnalyzer) | ||
| { | ||
| this.typeAnalyzer = requireNonNull(typeAnalyzer, "typeAnalyzer is null"); | ||
| } | ||
|
|
||
| @Override | ||
| public Pattern<FilterNode> getPattern() | ||
| { | ||
| return filter() | ||
| .with(source().matching(tableScan().capturedAs(CHILD))); | ||
| } | ||
|
|
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| @Override | ||
| public Result apply(FilterNode node, Captures captures, Context context) | ||
| { | ||
| Set<DereferenceExpression> dereferences = extractDereferences(ImmutableList.of(node.getPredicate()), true); | ||
| if (dereferences.isEmpty()) { | ||
| return Result.empty(); | ||
| } | ||
|
|
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| Assignments assignments = Assignments.of(dereferences, context.getSession(), context.getSymbolAllocator(), typeAnalyzer); | ||
| Map<Expression, SymbolReference> mappings = HashBiMap.create(assignments.getMap()) | ||
| .inverse() | ||
| .entrySet().stream() | ||
| .collect(toImmutableMap(Map.Entry::getKey, entry -> entry.getValue().toSymbolReference())); | ||
|
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| PlanNode source = node.getSource(); | ||
| return Result.ofPlanNode(new ProjectNode( | ||
| context.getIdAllocator().getNextId(), | ||
| new FilterNode( | ||
| context.getIdAllocator().getNextId(), | ||
| new ProjectNode( | ||
| context.getIdAllocator().getNextId(), | ||
| source, | ||
| Assignments.builder() | ||
| .putIdentities(source.getOutputSymbols()) | ||
| .putAll(assignments) | ||
| .build()), | ||
| replaceExpression(node.getPredicate(), mappings)), | ||
| Assignments.identity(node.getOutputSymbols()))); | ||
| } | ||
| } |
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