Replace regex-based LIKE matching with a linear-time direct matcher#4235
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arnaud-lacurie wants to merge 4 commits into
Open
Replace regex-based LIKE matching with a linear-time direct matcher#4235arnaud-lacurie wants to merge 4 commits into
arnaud-lacurie wants to merge 4 commits into
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PatternForLikeValue previously translated SQL LIKE patterns into Java regex strings (% → .*, _ → .) and LikeOperatorValue compiled them via Pattern.compile() per evaluated row. Java's NFA engine backtracks super-polynomially on patterns like %a%a%a%, making this a CPU-exhaustion vector for any caller that can submit a LIKE query. Replace the regex pipeline with a two-pointer iterative LIKE matcher that runs in O(n·m) time with no backtracking. PatternForLikeValue now emits a normalized LIKE pattern (% and _ as wildcards, \ as escape) instead of a regex string. Pattern.compile is gone entirely.
When text contained '%' at a position where the pattern also had '%', the literal equality branch fired before the wildcard branch, causing '%' in the pattern to be consumed as a literal match. Move the '%' wildcard check before the literal equality check and add regression test cases.
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Summary
PatternForLikeValuewas translating SQL LIKE patterns into Java regex strings (%→.*,_→.), andLikeOperatorValuewas compiling them viaPattern.compile()on every evaluated row. Java's NFA engine backtracks super-polynomially on patterns like%a%a%a%, which is a CPU-exhaustion risk for any caller that can submit a LIKE query.PatternForLikeValue.eval()now emits a normalized LIKE pattern (%/_as wildcards,\as internal escape) rather than a regex string.Pattern.compileis removed entirely.LikeOperatorValueTestcases pass unchanged.