kvdb/sqlbase: make NextSequence atomic, using a single SQL statement #9676
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The previous implementation of NextSequence was prone to race conditions as it read the sequence, incremented it locally, and then wrote it back. This commit modifies the function to use an atomic `UPDATE ... RETURNING` SQL statement. This may have been the cause of some of the excessive conflicts we've been seeing when using postgres in the kv operating mode. This change ensures that incrementing and retrieving the next sequence number for a nested bucket is performed atomically by the database, preventing potential duplicate sequence numbers under concurrent access. The query uses `COALESCE` to handle the initial NULL case, treating it as 0 before incrementing. Error handling is improved to cover cases where the bucket ID might not be found.
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In this commit, we optimize the Delete operation. Before we'd _always_ perform a `SELECT` first before deletion. Now we'll attempt to delete it as a non-bucket, if that works, then we can return. If that fails, then we'll do the `SELECT` to determine if the key doesn't exist, or if it's actually a bucket.
Similar to the write bucket, we can optimize for the case where the key already exists, allowing us to skip the extra `SELECT` statement.
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Pushed two other commits attempting to optimize the way |
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kvdb/sqlbase/readwrite_bucket.go:388
- The code after the 'return nil' on line 381 is unreachable, which indicates redundant error handling logic. Consider removing or refactoring the unreachable code to improve clarity.
return fmt.Errorf("error checking if key %x exists as bucket: %w", key, err)
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@ziggie1984: review reminder |
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The previous implementation of NextSequence was prone to race conditions as it read the sequence, incremented it locally, and then wrote it back. This commit modifies the function to use an atomic
UPDATE ... RETURNINGSQL statement.This may have been the cause of some of the excessive conflicts we've been seeing when using postgres in the kv operating mode.
This change ensures that incrementing and retrieving the next sequence number for a nested bucket is performed atomically by the database, preventing potential duplicate sequence numbers under concurrent access. The query uses
COALESCEto handle the initial NULL case, treating it as 0 before incrementing. Error handling is improved to cover cases where the bucket ID might not be found.