hint-bit · shipping · also PostgreSQL hint bit, tuple hint bits

Hint bit

A PostgreSQL hint bit is a tuple-header flag caching transaction-status information used to determine row visibility.

Visibility checks can set hint bits and dirty a page during a read, without changing application row values. SetHintBits in REL_18_0 also checks persistence ordering before recording committed status. [1]

wal_log_hints controls WAL protection for hint-only changes, not the use of hint bits. Data checksums require that protection regardless of the setting. [2]

Relations

related
full-page-write, write-ahead-log, database-checkpoint

Citations

  1. PostgreSQL REL_18_0: heapam_visibility.c, SetHintBits and visibility checks (accessed 2026-10-16)
  2. PostgreSQL 18: WAL settings, hint logging and image compression (accessed 2026-10-16)

Further reading

  1. Hesela: WAL page images, hint-bit changes and measurement boundaries (accessed 2026-10-16)
Sources & caveats

JSON: /data/terms/hint-bit.json