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perf: trim per-parse allocations that do no work - #2874
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manticore-projects merged 4 commits intoOct 31, 2026
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`Condition()` created a deque for leading `NOT` and `!` prefixes on every call, though few conditions have one. An empty `ArrayDeque` allocates its 17-slot array up front, so parsing `performance.sql` allocated 585 KB per parse for deques that stayed empty. The deque is now created at the first `NOT` or `!`.
`KeyWord.from` runs for every `LIKE`-family condition the parser builds, and `String.replaceAll` compiled its `\s+` pattern on each call. Parsing `performance.sql` allocated 201 KB per parse for those compilations. The pattern is now a precompiled constant.
…t use `PrimaryExpression()` created two lists on every call: one for chained signs such as `- -1` and one for JSON operators such as `->`. Nearly every primary expression has neither, so both lists usually stayed empty. They are now created at their first element.
`consumeXmlLeadingKeyword` and `FunctionArgumentList` called `Function.getName()` for every function to check for `XMLPARSE`, `XMLELEMENT` or `XMLFOREST`, and `getName()` joins the name parts into a new string on each call. Both checks now compare the single name part.
knutwannheden
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Good work, thank you much for tracing and improving this! |
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Conflicts in JSqlParserCC.jjt, resolved by keeping master's logic and re-adding the node links on top: - PARTITION BY (JSQLParser#2878): the four sites call ComplexExpressionList() directly and still link the PARTITION BY node. - PrimaryExpression (JSQLParser#2874): innerSigns is null without an inner sign, so the loop that wraps and links signed values is guarded. - Condition (JSQLParser#2874): one lazily created deque of NOT tokens carries both the token for the node and whether it was spelled "!".
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Parsing
performance.sql, the JMH benchmark's input, allocates 7.17 MB per parse on master, and about 1 MB of that (15%) does no work. The profile taken for #2870 found the sources: collections created on every call of a production but filled only on a rare path, a regex compiled for everyLIKE, and function names joined into a string just to compare them.This PR is separate from #2870 so each PR's benchmark stays clean.
Condition()created a deque for leadingNOTand!prefixes on every call, though few conditions are negated. An emptyArrayDequeallocates its 17-slot array up front. The deque is now created at the firstNOTor!, as fix: give every parsed object a node spanning its source #2870 already does for the token deque beside it.PrimaryExpression()created two lists on every call, for chained signs such as- -1and for JSON operators such as->. Both are now created at their first element.LikeExpression.KeyWord.fromcalledString.replaceAll("\\s+", "_"), which compiles the pattern on every call. The pattern is now a static constant.consumeXmlLeadingKeywordandFunctionArgumentListcalledFunction.getName()for every function to check forXMLPARSE,XMLELEMENTorXMLFOREST, andgetName()joins the name parts into a new string each time. Both now compare the single name part.Behaviour is unchanged, so there are no new tests.
ExpressionPrecedenceTestpins stacked prefixes (not !1 = 1deparses asNOT ! 1 = 1),DuckDBTestthe chained signs,JsonExpressionRenderingTestthe JSON operators,XmlForestTestthe XML keywords andLikeExpressionTestthe multi-wordSIMILAR TO../gradlew jmh -PjmhProfiler=gc, alternating master (a075737) and this branch on the same machine.gc.alloc.rate.normis bytes per parse:The branch is 2.4% faster in both runs while the 5.4 control moves 2% either way, so the time difference is at the edge of what this benchmark resolves. The allocation difference is not in doubt.
The
Condition()change edits the same lines as #2870, so whichever merges second has a small conflict to resolve. Both deques can then be created together at the firstNOTor!.