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fix(sql): memory leak when querying a table which is being ALTERed concurrently#6055

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bluestreak01 merged 3 commits intomasterfrom
jh_leak_filter_alter_race
Aug 15, 2025
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fix(sql): memory leak when querying a table which is being ALTERed concurrently#6055
bluestreak01 merged 3 commits intomasterfrom
jh_leak_filter_alter_race

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@jerrinot
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@jerrinot jerrinot commented Aug 15, 2025 •
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In rare cases where queries execute while a table is being ALTERed simultaneously, memory could leak during internal query retries. This edge case only affected systems with concurrent schema modifications and queries on the same table. While queries completed successfully through automatic retries, memory from failed attempts was not released.

Implementation details

The issue occurred when the SQL compiler attempted to create a filter during query compilation:

  1. Compiler creates a factory
  2. Attempts to wrap it in a filter
  3. Filter creation tries to obtain a cursor, which can fail due to TableReferenceOutOfDateException
  4. On failure, the factory wasn't being freed before the retry

@jerrinot jerrinot added Bug Incorrect or unexpected behavior SQL Issues or changes relating to SQL execution Java Improvements that update Java code labels Aug 15, 2025
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@bluestreak01 bluestreak01 merged commit 5935cce into master Aug 15, 2025
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@bluestreak01 bluestreak01 deleted the jh_leak_filter_alter_race branch August 15, 2025 14:13
@glasstiger
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glasstiger commented Aug 15, 2025

[PR Coverage check]

😞 fail : 0 / 5 (00.00%)

file detail

path covered line new line coverage
🔵 io/questdb/griffin/SqlCodeGenerator.java 0 5 00.00%

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@bluestreak01 bluestreak01 bluestreak01 approved these changes

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Bug Incorrect or unexpected behavior Java Improvements that update Java code SQL Issues or changes relating to SQL execution

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