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Banner: Postgres prepared statement becomes slow after switching to a generic plan

Databases Bug Report

Postgres prepared statement turns slow after the fifth run: the generic plan trap

John Nguyen · May 2, 2025 · 10 min read

The same query ran in 2 ms from psql and 4 seconds from our Go service, but only for some tenants and only after a connection had been alive for a while. Postgres had switched the prepared statement to a generic plan on its sixth execution.

Banner: a number dispenser handing out ticket numbers that are already taken

Databases Bug Report

Postgres duplicate key value violates unique constraint pkey after bulk import

Daniel Tran · Mar 25, 2025 · 8 min read

After importing 410,000 tickets with their original ids, most new tickets failed with duplicate key value violates unique constraint tickets_pkey, while a few succeeded. The id sequence was still at 1. Here is why, and how we resynced every sequence safely.