LOB compression + deduplication for query stats tables (#419)#433
Merged
erikdarlingdata merged 1 commit intodevfrom Mar 5, 2026
Merged
LOB compression + deduplication for query stats tables (#419)#433erikdarlingdata merged 1 commit intodevfrom
erikdarlingdata merged 1 commit intodevfrom
Conversation
Databases were growing to 150-200 GB in under a week on busy servers.
LOB columns (query_text, query_plan_text, query_sql_text, compilation_metrics)
were 92-94% of storage. COMPRESS()/DECOMPRESS() achieves 90-91% reduction.
Schema changes:
- query_stats, query_store_data, procedure_stats: LOB columns changed from
nvarchar(max)/xml to varbinary(max) with COMPRESS() on write
- Dropped unused query_plan xml columns
- Added row_hash binary(32) for deduplication
- Added tracking tables (query_stats_latest_hash, procedure_stats_latest_hash,
query_store_data_latest_hash) for efficient hash lookups
Collector changes (08, 09, 10):
- COMPRESS() on all text/plan INSERT expressions
- collect_query/collect_plan flag support added to query_stats and procedure_stats
- HASHBYTES('SHA2_256', binary_concat) dedup: only INSERT rows where metrics changed
- MERGE source deduped with ROW_NUMBER() to prevent duplicate key errors
Read-side changes:
- All reporting views (46, 47) wrap compressed columns in DECOMPRESS()
- Dashboard C# queries updated with DECOMPRESS() in SQL strings
Upgrade path:
- Batched DELETE WITH OUTPUT migration compresses existing data in place
- IDENTITY reseed preserves ID continuity
- Old tables renamed to _old for safety (manual DROP later)
Version bump: 2.1.0 → 2.2.0 across all four projects.
Tested: clean install (sql2016), CLI upgrade (sql2017, sql2019, sql2022),
GUI upgrade (sql2025). All collectors healthy, dedup validated, all views
and MCP tools return readable decompressed data.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
query_text,query_plan_text,query_sql_text,compilation_metrics) — 90-91% storage reductionStorage reduction (sql2022)
Test plan
🤖 Generated with Claude Code