fix: big offset error

[facetosea]

Description

Issue(s)

• Close/close/Fix/fix/Resolve/resolve: Issue Link

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[gemini-code-assist]

Summary of Changes

Hello @facetosea, 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 addresses a critical offset error in the doGroupResultSlimit function, which is responsible for processing SLIMIT and OFFSET clauses in query results. The changes ensure that data blocks are correctly trimmed and offsets are accurately applied, preventing incorrect result sets. To validate this fix, a comprehensive new test suite has been added, specifically targeting UNION queries combined with LIMIT and OFFSET, thereby enhancing the reliability of data retrieval operations.

Highlights

• Offset Logic Correction: The core logic within doGroupResultSlimit in groupoperator.c has been refined to correctly handle remainGroupOffset, ensuring that rows are properly skipped and the offset is fully consumed before further processing.
• Redundant Null Checks Removed: Unnecessary null checks for pLimitInfo have been removed, streamlining the code and improving readability.
• Early Exit Optimization: An early exit condition (return TSDB_CODE_SUCCESS;) was added when the remaining offset completely consumes the current data block, preventing redundant operations.
• New Test Cases for Offset: A new test method, GroupAggWithOffset, has been introduced in test_slimit_limit.py to thoroughly validate the LIMIT and OFFSET functionality, especially in complex UNION query scenarios, ensuring the fix is robust.

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[gemini-code-assist]

Code Review

This pull request addresses a bug in handling large offsets within the doGroupResultSlimit function. The updated logic correctly manages remainGroupOffset across data blocks and ensures an early return when a block is entirely skipped by an offset. Additionally, the code is simplified by removing redundant null checks for pLimitInfo, which is guaranteed to be non-null in that context. To support this fix, a new test suite, GroupAggWithOffset, has been introduced. It effectively validates the fix with various LIMIT and OFFSET scenarios on UNION queries. My review includes a suggestion to refactor the new test code for better maintainability by reducing code duplication.

[Copilot]

Pull request overview

This pull request fixes an offset handling bug in the group query operator. The issue was that remainGroupOffset was being reset prematurely, causing incorrect behavior when applying OFFSET to query results.

• Fixed the offset logic in doGroupResultSlimit() to properly handle remaining offset across multiple result blocks
• Added comprehensive test coverage for UNION queries with various LIMIT and OFFSET combinations
• Removed redundant null checks for already-validated pointer

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
source/libs/executor/src/groupoperator.c	Fixed offset handling logic by ensuring remainGroupOffset is only reset after being fully consumed, and adding early return when offset consumes all rows
test/cases/07-DataQuerying/07-SLimit/test_slimit_limit.py	Added new test method GroupAggWithOffset() with comprehensive test cases validating LIMIT/OFFSET behavior on UNION queries with large datasets

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