improvement(tables): bump rows version once at commit and serialize same-value unique writes by waleedlatif1 · Pull Request #8335 · simstudioai/sim

waleedlatif1 · 2026-09-26T18:02:33Z

Summary

bump_user_table_rows_version ran as a statement-level trigger inside every row-update statement, so each writer locked its table's user_table_definitions row across the rest of its transaction (executions patch, provenance write and capture, synchronous commit), and concurrent writers to one table queued behind each other. Provenance-only updates bumped it too, even though they don't change the table's content
The UPDATE bump is now a row-level DEFERRABLE INITIALLY DEFERRED constraint trigger AFTER UPDATE OF data, order_key, with a WHEN on real changes. It bumps once per table per transaction at commit, deduped through one transaction-local setting. INSERT/DELETE statement bumps are unchanged. The only readers (the CSV snapshot cache and mount safety) read outside write transactions, so a commit-time bump keeps their read, scan, re-read checks intact
user_table_rows.table_id → user_table_definitions FK becomes DEFERRABLE INITIALLY DEFERRED (catalog-only). The write path updates a row twice in one transaction (data, then the provenance marker, which the rolling-deploy demote trigger requires to be separate), and the second update re-checked the FK, taking a key-share lock on the definition row that the commit-time bump then waited behind. ON DELETE CASCADE stays immediate, and nothing catches this FK's error inline
The trigger swap runs inside an explicit BEGIN, so it stays atomic when an earlier migration in the same deploy used a COMMIT breakpoint
CREATE STATISTICS (dependencies) ON workspace_id, table_id plus ANALYZE, so the planner stops underestimating per-table row counts and serves data @> filters from the tenant GIN
Unique columns are an application-level check, so two concurrent writes of the same value could both pass it and both commit. Every write path now takes transaction-scoped advisory locks (tag user_table_unique_value) before its check: the table's unique lock shared, then an exclusive lock per value, keyed on the same normalization the check uses (so '8' and 8 share a key). Writers of different values, on any column, never wait on each other
- Each transaction takes all its locks at once, in one sorted order. The global order is schema lock, then unique locks, then row-order lock, then definition row
- A json object or array value, or a transaction that would take more than 64 value locks, takes the table's unique lock exclusively instead. Whole-table replace and every import batch always do. A transaction holds at most 1 + 64 unique locks, however many unique columns the table has. 64 is the default per-connection budget of Postgres's shared lock table, so wide schemas and large batches can't exhaust it and fail unrelated queries
- The unique check for updateRow, batchUpdateRows, and single-row filter updates now runs inside the write transaction, under the locks. batchUpdateRows also rejects two updates in one batch that set the same value, and it locks and checks only the unique columns each update changes
- Tables without unique columns take no extra round trips

Type of Change

Improvement

Testing

A/B against staging on identical fresh DBs, real service functions, runs alternated:
- 20 concurrent updateRow writers on one table: 943–1071 → 1585–1606 ops/s, p99 77–107 → ~18 ms, lock wait 521–525 → 4–8 backend-s
- 50 writers: 886–937 → 1398–1450 ops/s, p99 274–292 → 124–159 ms
- Provenance-only writes: 5185–5482 → 7979–8713 ops/s, p99 ~15 → ~4 ms
- Inserts with a unique column and executions-only writes: within noise
- Large single-transaction rewrites are ~20% faster, with ~0.6s of commit-time trigger work at 1M rows
Filter queries on 4,000 tables with skewed sizes: large-table data @> filters 1.7–5.7 → 0.5 ms
Migration-during-writes: 0 missed bumps across 3 runs (without the BEGIN, 40/40 missed)
row-writes.integration.ts: data and reorder edits bump once per transaction, including two tables in one transaction; provenance-only, timestamp-only, no-op, and executions-only writes don't bump; a second writer commits while the first is uncommitted; the snapshot re-keys when a writer commits mid-materialization. These fail on the old trigger
Fresh DB migrate plus replay, secret-provenance and table integration suites, table unit suites, type-check, lint, check:audits, and check:migrations origin/staging pass
Unique races (deterministic, driven by pg_locks wait states), all ending with one row:
- same-value single inserts
- '8' vs 8
- batch vs single insert
- updateRow vs insert
- import batch vs insert
- a batch over the value-lock cap vs a per-value writer
- a replace adding the first unique column vs a writer on the older schema (no deadlock)
- a 100-unique-column table holding a single lock
- two updates in one batch setting the same value
Different values don't wait on each other. Each race test fails on the pre-fix code
Unique-column throughput vs staging is within noise: distinct-value inserts, batch inserts, and batch upserts at 10 and 50 writers. updateRow keeps the gains above
Migration is 0390 on top of staging

Checklist

Code follows project style guidelines
Self-reviewed my changes
Tests added/updated and passing
No new warnings introduced
I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

vercel · 2026-09-26T18:02:36Z

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greptile-apps · 2026-09-26T18:06:57Z

Confidence Score: 5/5

[Critical risk] Restructures row-write locking and adds database migration.

The PR appears safe to merge; no new actionable issue or outstanding previous finding remains.

Summary

The PR defers row-update version bumps until commit and adds transaction-scoped locks around application-level unique checks.

UPDATEs that change row data or order now bump each table’s version once per transaction; provenance-only writes do not.
Unique-value writes serialize before checking for conflicts, with a table-wide lock for large batches and imports.
The latest changes canonicalize JSON object keys for batch duplicate detection and release a test writer when its lock-wait assertion fails.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[Begin row-write transaction] --> B[Acquire unique-value or table-wide lock]
  B --> C[Check uniqueness]
  C --> D[Acquire row-order lock if needed]
  D --> E[Write rows]
  E --> F[Commit]
  F --> G[Deferred UPDATE trigger bumps rows_version once per table]

_{Reviews (10) · Last reviewed commit: "fix(tables): key unique JSON values by c..."}

waleedlatif1 · 2026-09-26T18:28:01Z

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waleedlatif1 · 2026-09-26T19:04:51Z

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waleedlatif1 · 2026-09-26T19:08:57Z

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waleedlatif1 · 2026-09-26T23:29:49Z

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waleedlatif1 · 2026-09-27T02:01:29Z

@greptile re the concurrent-unique-insert risk in the summary: this PR doesn't change unique-constraint behavior. insertRow, batch insert, and upsert's insert branch are byte-identical to staging. An earlier revision moved the unique check under the per-table append lock, which closed the race but serialized every insert into a table with a unique column (2.5–10× slower under concurrency). That revision was reverted, so this PR doesn't touch the race either way. The race exists on staging today; fixing it properly needs per-value locks (table, column, normalized value), and that goes in a separate PR with its own benchmark. This PR only changes the rows_version trigger, the row FK's deferrability, and the planner statistic.

greptile-apps · 2026-09-27T02:01:56Z

You’re right: the concurrent unique-insert race is not introduced or changed by this PR. The changed application code contains no insert, batch-insert, or upsert-branch edits, and the migration only changes the rows-version triggers, FK deferrability, and planner statistics.

I’m withdrawing that critical-risk finding from this review; it should be addressed separately with the per-value locking design and its own concurrency benchmarks.

…h per-value advisory locks

…ck unique columns on every import batch Lower the per-transaction value-lock cap to 64 so concurrent writers cannot exhaust the shared lock table; larger writes keep the exclusive column-lock fallback. Import batches now take the unique-column locks and run their unique check inside their transaction, batchUpdateRows rejects two updates writing the same unique value and locks and checks only the unique columns each update changes, and the 0390 comment describes the mechanism only.

…ocks

waleedlatif1 · 2026-09-28T03:34:17Z

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… schemas stay within the lock budget

waleedlatif1 · 2026-09-28T03:52:51Z

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…ver hides a batch duplicate

waleedlatif1 · 2026-09-28T04:04:22Z

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waleedlatif1 force-pushed the improvement/table-rows-version-at-commit branch from dba8085 to ecb119e Compare September 26, 2026 23:29

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fix(knowledge): resume the member resurrection walk from a persisted cursor #8365

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waleedlatif1 added 5 commits September 27, 2026 19:29

improvement(tables): bump a table's rows version once at commit

65895bf

fix(tables): serialize concurrent writes of the same unique value wit…

49d4904

…h per-value advisory locks

fix(tables): take the batched advisory locks on a transaction

16ee1d8

chore(tables): share one unique-value key between the check and the l…

97cb317

…ocks

waleedlatif1 force-pushed the improvement/table-rows-version-at-commit branch from 1d520f6 to 97cb317 Compare September 28, 2026 03:34

waleedlatif1 changed the title ~~improvement(tables): bump a table's rows version once at commit~~ improvement(tables): bump rows version once at commit and serialize same-value unique writes Sep 28, 2026

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fix(tables): lock a table's unique values under one table key so wide…

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Type of Change

Testing

Checklist

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