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Sarj Standards

SQL · performance

index-concurrently

sql:index-concurrently

CREATE INDEX without CONCURRENTLY — locks the table against writes.

Code
SARJ108
Default
error
Fix
none
Languages
sql

Why

Building an index normally blocks writes to an existing PostgreSQL table for the duration of the build.

Fix

Use CREATE INDEX CONCURRENTLY in a nontransactional migration.

Before / after

Executed by this rule’s unit tests.

Before

Blocking index build on an existing table

migrations/002_email_index.sql · focus
CREATE INDEX users_email_idx ON users(email);

After

Concurrent index build

migrations/002_email_index.sql · focus
CREATE INDEX CONCURRENTLY users_email_idx ON users(email);

Limits

  • Indexes on tables created earlier in the same file are exempt because no concurrent writers exist yet.