fix: LazyMemoryExec should produce independent streams per execute()#21565
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viirya merged 1 commit intoapache:mainfrom Apr 14, 2026
Merged
fix: LazyMemoryExec should produce independent streams per execute()#21565viirya merged 1 commit intoapache:mainfrom
viirya merged 1 commit intoapache:mainfrom
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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: Isaac
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…pache#21565) ## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes apache#123` indicates that this PR will close issue apache#123. --> - 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 (apache#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. ## Are these changes tested? <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> Unit test ## Are there any user-facing changes? No <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. -->
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Which issue does this PR close?
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.
Are these changes tested?
Unit test
Are there any user-facing changes?
No