[Terr_]

> Finally, hash indexes always require that the found row be confirmed in the data table

Probably to avoid returning the wrong result for statistically-inevitable collisions, right?

[agacera]

Probably it is needed to check if the row is still visible to that transaction.

[colanderman]

Postgres uses a visibility bitmap [1] to avoid hitting the heap merely to determine visibility of stable data.

[1] https://www.postgresql.org/docs/9.6/static/indexes-index-onl...

[colanderman]

Correct.