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Posted to github@datafusion.apache.org by "viirya (via GitHub)" <gi...@apache.org> on 2026/04/12 06:17:52 UTC

[PR] fix: LazyMemoryExec should produce independent streams per execute() [datafusion]

viirya opened a new pull request, #21565:
URL: https://github.com/apache/datafusion/pull/21565

   ## Which issue does this PR close?
   
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   - Closes #.
   
   ## Rationale for this change
   
   LazyMemoryExec::execute() shares the same generator instance across multiple calls via Arc::clone, so a second call to execute(0) continues from where the first left off instead of starting from the beginning. This is inconsistent with how other ExecutionPlan implementations behave, where each execute() call produces an independent stream. This was discovered while writing e2e tests for NestedLoopJoinExec memory-limited execution (#21448), where the OOM fallback path re-executes the left child plan and got incomplete results. 
   
   ## What changes are included in this PR?
   
   LazyMemoryExec::execute() was sharing the same generator instance (via Arc::clone) across multiple calls, causing streams to share mutable state. This meant a second call to execute(0) would continue from where the first call left off, instead of starting from the beginning.
   
   Fix by calling reset_state() on the generator to create a fresh instance for each execute() call, matching the expected ExecutionPlan semantics that each execute() produces an independent stream.
   
   Co-authored-by: Claude Code
   
   ## Are these changes tested?
   
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   Unit test
   
   ## Are there any user-facing changes?
   
   No
   
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Re: [PR] fix: LazyMemoryExec should produce independent streams per execute() [datafusion]

Posted by "viirya (via GitHub)" <gi...@apache.org>.
viirya commented on PR #21565:
URL: https://github.com/apache/datafusion/pull/21565#issuecomment-4240956136

   Thanks @2010YOUY01 


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Re: [PR] fix: LazyMemoryExec should produce independent streams per execute() [datafusion]

Posted by "viirya (via GitHub)" <gi...@apache.org>.
viirya merged PR #21565:
URL: https://github.com/apache/datafusion/pull/21565


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