Implement reverse performance optimization
#4056
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,128 @@ | ||
| /* | ||
| * Copyright OpenSearch Contributors | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
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| package org.opensearch.sql.calcite.rule; | ||
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| import org.apache.calcite.plan.RelOptRule; | ||
| import org.apache.calcite.plan.RelOptRuleCall; | ||
| import org.apache.calcite.rel.logical.LogicalSort; | ||
| import org.apache.logging.log4j.LogManager; | ||
| import org.apache.logging.log4j.Logger; | ||
| import org.opensearch.sql.calcite.plan.LogicalSystemLimit; | ||
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| /** Combines consecutive sorts with opposite directions into 1 sort. */ | ||
| public class SortDirectionOptRule extends RelOptRule { | ||
| private static final Logger LOG = LogManager.getLogger(SortDirectionOptRule.class); | ||
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| public static final SortDirectionOptRule INSTANCE = new SortDirectionOptRule(); | ||
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| private SortDirectionOptRule() { | ||
| super( | ||
| operand(LogicalSort.class, | ||
| operand(org.apache.calcite.rel.RelNode.class, | ||
| operand(LogicalSort.class, any()))), | ||
| "SortDirectionOptRule"); | ||
| } | ||
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| @Override | ||
| public boolean matches(RelOptRuleCall call) { | ||
| LogicalSort outerSort = call.rel(0); | ||
| org.apache.calcite.rel.RelNode intermediate = call.rel(1); | ||
| LogicalSort innerSort = call.rel(2); | ||
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| LOG.debug("SortDirectionOptRule.matches() - outer: {}, intermediate: {}, inner: {}", | ||
| outerSort, intermediate, innerSort); | ||
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| // Only allow single-input intermediate nodes (like LogicalProject) | ||
| if (intermediate.getInputs().size() != 1) { | ||
| LOG.debug("Intermediate node has {} inputs, expected 1", intermediate.getInputs().size()); | ||
| return false; | ||
| } | ||
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| // Don't optimize if inner sort has a fetch limit (head/limit before sort) | ||
| // This preserves limit-then-sort semantics | ||
| // Example: source=t | head 5 | sort field | reverse | ||
| // Plan: Sort(reverse) -> Sort(field, fetch=5) -> Scan | ||
| // Should NOT be optimized to preserve the "take first 5, then sort" behavior | ||
| if (innerSort.fetch != null) { | ||
| LOG.debug("Skipping: inner sort has fetch limit: {}", innerSort.fetch); | ||
| return false; | ||
| } | ||
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| // Must be same field with opposite directions (sort | reverse pattern) | ||
| boolean matches = hasSameFieldWithOppositeDirection(outerSort, innerSort); | ||
| LOG.debug("Same field with opposite direction: {}", matches); | ||
| return matches; | ||
| } | ||
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| @Override | ||
| public void onMatch(RelOptRuleCall call) { | ||
| LogicalSort outerSort = call.rel(0); | ||
| org.apache.calcite.rel.RelNode intermediate = call.rel(1); | ||
| LogicalSort innerSort = call.rel(2); | ||
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| LOG.debug("SortDirectionOptRule.onMatch() transforming: {} -> {}", outerSort, innerSort); | ||
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| // Create optimized sort with the final direction | ||
| LogicalSort optimizedSort = | ||
| LogicalSort.create( | ||
| innerSort.getInput(), outerSort.getCollation(), outerSort.offset, outerSort.fetch); | ||
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| // Recreate the intermediate node with the optimized sort as input | ||
| org.apache.calcite.rel.RelNode newIntermediate = | ||
| intermediate.copy(intermediate.getTraitSet(), | ||
| java.util.Collections.singletonList(optimizedSort)); | ||
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| LOG.debug("Transformed to: {}", newIntermediate); | ||
| call.transformTo(newIntermediate); | ||
| } | ||
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| private boolean hasSameFieldWithOppositeDirection(LogicalSort outerSort, LogicalSort innerSort) { | ||
| var outerFields = outerSort.getCollation().getFieldCollations(); | ||
| var innerFields = innerSort.getCollation().getFieldCollations(); | ||
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| if (outerFields.isEmpty() || innerFields.isEmpty()) { | ||
| LOG.debug("No field collations found"); | ||
| return false; | ||
| } | ||
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| // Must have same number of fields | ||
| if (outerFields.size() != innerFields.size()) { | ||
| LOG.debug( | ||
| "Different number of sort fields: outer={}, inner={}", | ||
| outerFields.size(), | ||
| innerFields.size()); | ||
| return false; | ||
| } | ||
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| // Check all fields have same index but opposite directions | ||
| for (int i = 0; i < outerFields.size(); i++) { | ||
| var outerField = outerFields.get(i); | ||
| var innerField = innerFields.get(i); | ||
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| LOG.debug( | ||
| "Field {}: outer(index={}, direction={}), inner(index={}, direction={})", | ||
| i, | ||
| outerField.getFieldIndex(), | ||
| outerField.getDirection(), | ||
| innerField.getFieldIndex(), | ||
| innerField.getDirection()); | ||
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| if (outerField.getFieldIndex() != innerField.getFieldIndex() | ||
| || outerField.getDirection() == innerField.getDirection()) { | ||
| LOG.debug( | ||
| "Field {} mismatch: same index={}, opposite direction={}", | ||
| i, | ||
| outerField.getFieldIndex() == innerField.getFieldIndex(), | ||
| outerField.getDirection() != innerField.getDirection()); | ||
| return false; | ||
| } | ||
| } | ||
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| LOG.debug("All fields match with opposite directions"); | ||
| return true; | ||
| } | ||
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| } | ||
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So we assume the head of this collation list must come from the
sortcommand right beforereversecommand right? Is it always true or the reverse logic below works even though it's not true?There was a problem hiding this comment.
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For Q2: Take query
... | sort | X | Y | Z | reversefor example, we should be good as long as commands in-between (X, Y, Z) doesn't rely on the output order ofsortcommand, right? Just thinking any counterexample, such as... | sort | head | reverse?I'm thinking is it too early to do this in
visitReverse? Essentially, ourCalciteRelNodeVisitorconverts AST to its logical representation by RelNode. Just wondering what does it look like if we simply translate reverse to logical sort operator here?There was a problem hiding this comment.
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Great question about edge cases! I tested both
| sort | head 10 | reverseand| sort | eval | head | reversepatterns and they work correctly. In the first part of visitReverse the SORT ASC and LIMIT for head are combined intoLogicalSort(sort0=[$0], dir0=[ASC-nulls-first], fetch=[10])and then the reverseCollation is added withLogicalSort(sort0=[$0], dir0=[DESC-nulls-last]). The physical plan pushes SORT ASC + LIMIT N to OpenSearch, then applies DESC sort on the limited results. Let me know if there are any other edge cases, Thanks!