Transactional Range Split Isolation & Split Key Deferral

Engineering objective

System challenge

A declarative schema-change transaction created statistics-derived range splits before commit. When the transaction aborted, splits survived in KV. Subsequent descriptor reuse of the same index ID under a new schema caused surviving split keys to split inside column families or rows.

Constraints

Working within real limits

• ✕Preserve declarative schema changer lifecycle across pre-commit and post-commit backfill stages
• ✕Defer statistics-derived split-and-scatter execution to runBackfill in exec_backfill.go
• ✕Remove pre-commit split emission in schemachanger opgen
• ✕Verify with unit test TestIndexSplitAndScatterAbortedTransactionNoSurvivingSplits verifying zero surviving splits on abort

Approach

How it was built

1. 01

   Traced declarative schema changer lifecycle across pre-commit and post-commit backfill stages

2. 02

   Deferred statistics-derived split-and-scatter execution to runBackfill in exec_backfill.go

3. 03

   Removed pre-commit split emission in schemachanger opgen

4. 04

   Added unit test TestIndexSplitAndScatterAbortedTransactionNoSurvivingSplits verifying zero surviving splits on abort

Technical validation

Implementation evidence

Observable engineering evidence. Discipline: SYSTEMS HARDENING

Public evidence

Review the upstream contribution

Outcome

What was delivered

• Decoupled non-transactional AdminSplitRequest side-effects from uncommitted transactions

• Prevented stale split keys from persisting across transaction aborts

• All CockroachDB static analysis, blathers release-justification, and CLA checks green

Technologies

Stack and tools

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