fix: Further improve performance of the UTF-8 string comparison logic #1
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The semantics of this logic were originally fixed by googleapis#1967, but this fix caused a material performance degradation, which was then improved by googleapis#2021. The performance was, however, still suboptimal, and this PR further improves the speed back to close to its original speed and, serendipitously, simplifies the algorithm too. This commit effectively ports the following two PRs from the firebase-android-sdk repository: - firebase/firebase-android-sdk#7098 - firebase/firebase-android-sdk#7109
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Summary of Changes
Hello @dconeybe, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request delivers a crucial performance enhancement and simplification to the UTF-8 string comparison logic within the Firestore client library. It addresses prior performance regressions by introducing a highly optimized and more elegant algorithm for string ordering, ensuring efficient and correct data sorting.
Highlights
- Performance Optimization: The core
compareUtf8Stringsmethod inOrder.javahas been completely rewritten to significantly improve performance and simplify its logic. The new algorithm leverages the relationship between UTF-8 and UTF-16 representations for more efficient string comparison, avoiding costly byte string conversions. - Algorithm Simplification: The previous complex logic involving
codePointAtandByteString.copyFromUtf8for non-ASCII characters has been replaced with a more straightforward character-by-character comparison that intelligently handles surrogate pairs. - Test Robustness: The
OrderTest.javahas been updated to improve the robustness of thecompareUtf8Stringstest. Instead of asserting exact return values, it now checks thesignum(sign) of the comparison result, which is a more appropriate way to validate comparator behavior.
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Pull Request Overview
This PR further improves performance of Firebase’s UTF-8 string comparison by simplifying the algorithm and adjusts the corresponding tests to validate only the comparison sign.
- Simplified
compareUtf8StringsinOrder.javato a single-pass UTF-16 char comparison leveraging surrogate checks. - Updated
OrderTest.javato compare only the sign of results and introduced asignNamehelper for clearer error messages.
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| Order.java | Replaced the multi-step code-point and byte-encoding logic with a direct UTF-16 char loop using Character.isSurrogate and Character.compare for performance. |
| OrderTest.java | Changed test assertions to use Integer.signum, added signName(int) to describe result signs, and updated error output accordingly. |
Comments suppressed due to low confidence (1)
google-cloud-firestore/src/test/java/com/google/cloud/firestore/OrderTest.java:235
- The error message prints only the descriptive expected sign but omits the actual numeric expected value. For consistency with the
actualoutput, include(" + expected + ")aftersignName(expected)to display the numeric value as well.
+ signName(expected)
google-cloud-firestore/src/main/java/com/google/cloud/firestore/Order.java
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google-cloud-firestore/src/test/java/com/google/cloud/firestore/OrderTest.java
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This PR is a mirror of googleapis#2182
The semantics of the UTF-8 string comparison logic were originally fixed by googleapis#1967, but this fix caused a material performance degradation, which was then improved by googleapis#2021. The performance was, however, still sub-optimal, and this PR further improves the speed back to close to its original speed and, serendipitously, simplifies the algorithm too.
This PR effectively ports the following two PRs from the firebase-android-sdk repository: