core/vdbe: Short-circuit index seek on NULL keys in LEFT JOIN#6268
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friskypriyanshu wants to merge 4 commits intotursodatabase:mainfrom
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core/vdbe: Short-circuit index seek on NULL keys in LEFT JOIN#6268friskypriyanshu wants to merge 4 commits intotursodatabase:mainfrom
friskypriyanshu wants to merge 4 commits intotursodatabase:mainfrom
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friskypriyanshu
requested review from
jussisaurio,
penberg and
pereman2
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Fossier: Manual Review Requested
Score BreakdownTotal Score: 69.3/100 | Confidence: 100% | Outcome: REVIEW
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/fossier approve |
penberg
changed the title
Author
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Hi @penberg @jussisaurio, just a gentle ping on this one. All checks are green, including the fix for the fuzzer regression. Ready for review whenever you have a moment. Thanks! |
jussisaurio
reviewed
Apr 9, 2026
| }; | ||
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| if is_eq_only { | ||
| // We only care about Unpacked record sources for this short-circuit |
Collaborator
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isn't it invariant that this is RecordSource::Unpacked, since it's constructed above? Let's do let ... else instead of if let for that reason.
| if is_eq_only { | ||
| // We only care about Unpacked record sources for this short-circuit | ||
| if let RecordSource::Unpacked { start_reg, .. } = record_source { | ||
| // Check only the primary register (no need for a loop 'i' here) |
Collaborator
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Why is there no need? This should be part of the comment.
| if let RecordSource::Unpacked { start_reg, .. } = record_source { | ||
| // Check only the primary register (no need for a loop 'i' here) | ||
| if state.registers[start_reg].is_null() { | ||
| let offset = match target_pc { |
Collaborator
There was a problem hiding this comment.
You can use target_pc.as_offset_int() here which has equivalent behavior
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Fixes: #6077
Description
Fixes a query optimizer bug where chained LEFT JOINs producing virtual NULL keys were incorrectly matching literal NULLs in downstream indexed tables.
Root Cause & Fix
The VDBE op_seek instruction was evaluating NULL keys against the index instead of short-circuiting (violating NULL = NULL is false).
In core/vdbe/execute.rs (op_seek):
Intercepted RecordSource::Unpacked registers before calling seek_internal.
If any search register evaluates to Null, the seek instantly aborts.
Extracted target_pc to update state.pc directly and returned InsnFunctionStepResult::Step to correctly trigger the "not found" branch.
Testing
Added left_join_null_index_bug.sqltest using the exact schema/query from the issue.
Suite now passes cleanly with correct empty columns for unmatched rows.