PostgreSQL Field Notes

Notes for the problems that show up after launch: bad plans, awkward migrations, index debt, vacuum pressure, replica lag, and the small decisions that make PostgreSQL easier to operate.

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pgvector and RAG Indexes Slow Queries Locks and Transactions Backups and Durability Replication and WAL Connections and Pooling CPU, Memory, and I/O Vacuum and Bloat Cloud Providers

January 19, 20266 min read

Postgres Memory Pressure: Diagnosing OOMs and the Settings That Prevent Them

A Postgres OOM kill is one of the few crashes that is almost always preventable. The pattern is consistent enough to have a checklist.

January 18, 20265 min read

Temporary Files in Postgres: When Queries Spill to Disk and Why

Temp files are hidden disk work. They explain slow sorts, hash joins, and aggregations that look fine until work_mem runs out under real concurrency.

January 17, 20267 min read

When the Planner is Wrong: Fixing Bad Row Estimates in Postgres

Bad plans usually start with bad row estimates. Fix the first wrong estimate and the rest of the plan often stops looking mysterious.

January 16, 20268 min read

Slow Inserts in Postgres: It's Almost Always One of Three Things

Slow inserts are rarely just inserts. They are usually index maintenance, constraint and trigger work, WAL/checkpoint pressure, or a transaction pattern that makes every row pay retail.

January 15, 20268 min read

Slow Deletes in Postgres: It's Almost Never the Delete Itself

Slow deletes usually come from the work around the row: foreign keys, triggers, indexes, WAL, vacuum debt, and transaction size. The fix starts by finding what each deleted row has to pay for.

January 14, 20266 min read

Autovacuum Wraparound Emergency: What to Do When the Cluster is at Risk

Wraparound emergencies are preventable, but once warnings start you need a calm runbook: identify old XIDs, unblock vacuum, freeze priority tables, and protect availability.

January 13, 20266 min read

Postgres Plan Regressions After Deploy: When the Same Query Suddenly Got Slow

Plan regressions are painful because the SQL did not change. The work is proving the plan changed, finding the estimate or stats shift, and restoring the safe path.

January 12, 20265 min read

psql Tricks That Pay for Themselves: The Commands I Use Daily

psql is more capable than people use it for. A handful of meta-commands and shortcuts make it the most productive shell for database work.

January 11, 20265 min read

pg_stat_statements Retention: Don't Lose the History You Need

pg_stat_statements is cumulative since cluster start or last reset. If you reset it, you lose the data you would have used to debug the next incident.

January 10, 20268 min read

The Postgres Health Check I Run Before Blaming the App

A useful Postgres health check is not a wall of green checks. It is a short path from symptom to evidence: sessions, locks, slow SQL, vacuum, replication, and WAL.

January 9, 20265 min read

auto_explain in Postgres: Catching Bad Plans After They Happen

auto_explain is for the slow plan you cannot reproduce later. It captures the execution plan when the bad thing actually happens.

January 8, 20265 min read

pgbench for Load Testing: Useful, Limited, and Often Misinterpreted

pgbench measures Postgres throughput under a synthetic workload. It tells you something useful, but only if you understand what its numbers mean.