REINDEX and REINDEX CONCURRENTLY in PostgrSQL DBA



REINDEX and REINDEX CONCURRENTLY

In PostgreSQL, REINDEX and REINDEX CONCURRENTLY are used to rebuild corrupt or bloated indexes. They are essential tools for database maintenance and performance tuning.

REINDEX:

In practice indexes can become corrupted due to software bugs or hardware failures. REINDEX provides a recovery method.REINDEX provides a way to reduce the space consumption of the index by writing a new version of the index without the dead pages.

REINDEX rebuilds indexes from scratch. It's commonly used when:

  • Indexes are bloated (due to many UPDATE/DELETE operations).
  • Index corruption is suspected.
  • After a major PostgreSQL version upgrade (especially via pg_upgrade).
  • To improve performance of certain queries.

Parameters

REINDEX INDEX index_name;
REINDEX TABLE table_name;
REINDEX DATABASE db_name;
REINDEX SYSTEM db_name;

REINDEX CONCURRENTLY:

REINDEX CONCURRENTLY was introduced in PostgreSQL 12+ and allows index rebuilding without blocking reads and writes.

REINDEX CONCURRENTLY

  • You want to avoid downtime or user impact while fixing index bloat or corruption.
  • ebuilding a large index with regular REINDEX could lock the table for hours. REINDEX CONCURRENTLY avoids this by allowing writes and reads during the process.
  • If the table is used by active applications, background jobs, or APIs that can’t be paused.
  • Proactive Maintenance on Production :Schedule this during off-peak hours for non-disruptive index refresh.
REINDEX INDEX CONCURRENTLY index_name;

REINDEX TABLE CONCURRENTLY table_name; 

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