Rust: Fix bad join #21180
Open
Rust: Fix bad join #21180
+3
−2
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Before
```
Evaluated relational algebra for predicate _ElementImpl::Impl::MacroExpansion::isAttributeMacroExpansionSourceLocation/2#3429148c_Locatable::Lo__#antijoin_rhs@9f4aa4rk with tuple counts:
5127263380 ~4% {3} r1 = JOIN `_AstNodeImpl::Impl::AstNode#22e758cf_ElementImpl::Impl::MacroExpansion::getATokenTreeNode/1#a2df59a3__#shared` WITH `ElementImpl::Impl::MacroExpansion::isAttributeMacroExpansionSourceLocation/2#3429148c` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Lhs.0
305226 ~0% {2} | JOIN WITH `Locatable::Locatable.getLocation/0#dispred#f3f7e2b2` ON FIRST 2 OUTPUT Lhs.0, Lhs.2
return r1
```
(No After; the predicate is no longer generated)
Contributor
There was a problem hiding this comment.
Pull request overview
This PR optimizes a CodeQL query in the Rust library by fixing a performance issue caused by an inefficient join operation. The change introduces an intermediate variable to store the location before using it in a negative condition, significantly reducing tuple processing from ~5 billion to eliminating the problematic predicate entirely.
Changes:
- Introduced an intermediate variable
lto storen.getLocation()in theisFromMacroExpansionpredicate, preventing an expensive join operation
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
paldepind
approved these changes
Jan 16, 2026
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Before
(No After; the predicate is no longer generated)