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## Why `replica_heartbeat` is updated continuously, but autovacuum heap truncation can take an `ACCESS EXCLUSIVE` lock whose replay cancels concurrent hot-standby reads. Truncating a fixed, single-row table provides no meaningful space benefit. ## What - Add migration 0034 to set `vacuum_truncate = false` on `replica_heartbeat` - Keep the desired-state schema aligned for fresh installations - Extend migration coverage so both paths retain the reloption ## Risk Assessment Low — this disables only autovacuum's heap-truncation phase for a single-row table; normal vacuum cleanup remains enabled. The tradeoff is retaining at most the table's otherwise-truncatable tail pages. ## References - [Investigation thread](https://sq-block.slack.com/archives/C0B2WT43BDH/p1787760831375989) - [PostgreSQL table storage parameters](https://www.postgresql.org/docs/current/sql-createtable.html#SQL-CREATETABLE-STORAGE-PARAMETERS) Generated with Codex --- **Update Aug 27, 2026:** Hardened fresh `pgschema` bootstraps after review. - Renamed the shared post-apply script to `reconcile-schema-after-pgschema.sql` and made it restore the heartbeat reloption and singleton row idempotently. - Added live catalog and row assertions that stop bootstrap when the database does not match the required state. - Updated every repository `pgschema apply` caller, including the desktop release smoke path. - Added a regression test that requires future `pgschema apply` callers to run reconciliation. - Documented the `pgschema` DML and storage-parameter limitation in `AGENTS.md` and at the reconciliation entry point. - Merged current `main` and renumbered this migration to 0034 after `main` added migration 0033. --------- Signed-off-by: Luke Tornquist <tornquist@squareup.com>
8 lines
457 B
SQL
8 lines
457 B
SQL
-- replica_heartbeat is a single-row table updated continuously by every relay
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-- pod. Autovacuum heap truncation briefly takes ACCESS EXCLUSIVE on the table;
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-- replaying that lock on a hot standby can cancel concurrent heartbeat reads.
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-- The table cannot reclaim meaningful disk space by truncating one page, so
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-- disable only the truncation phase while retaining normal autovacuum cleanup.
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ALTER TABLE replica_heartbeat SET (vacuum_truncate = false);
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