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avoid quadratic member lookups in table and alias visitors - #2763
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manticore-projects merged 1 commit intoOct 11, 2026
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TablesNamesFinder tracked derived-table, CTE and lateral names in an ArrayList and matched every plain table reference against it, and AddAliasesVisitor checked each generated alias against a LinkedList, so both walked parsed SQL in O(n^2). Both collections are used only for membership, so back them with a LinkedHashSet. Signed-off-by: Javid Khan <dxbjavid@gmail.com>
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Kudos for knowing/understanding the Java Collection classes and Lists :-D |
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TablesNamesFinder remembers the names of derived tables, CTEs and lateral selects in otherItemNames and checks every plain table reference against it before recording it, but that collection was an ArrayList, so the membership test was linear and a statement with n aliased items and n table references took O(n^2) to walk through findTables. The same shape affects AddAliasesVisitor, where each generated alias is checked against the already used ones with a LinkedList.contains, so adding aliases to a select with n items was quadratic as well. Both collections are only ever used for membership, never for ordering, so backing them with a LinkedHashSet keeps the output identical while bringing both walks back to linear; I have added a timing regression test for each.