Re: Why is Hash index not transaction safe.

Wei Shan <weishan(dot)ang(at)gmail(dot)com> writes:
> I read the following about Hash indexes in Heroku's blog (
> https://devcenter.heroku.com/articles/postgresql-indexes)

> *Hash Indexes are only useful for equality comparisons, but you pretty much
> never want to use them since they are not transaction safe, need to be
> manually rebuilt after crashes, and are not replicated to followers, so the
> advantage over using a B-Tree is rather small.*

> Could anyone explain about why is it not transaction safe as compared to
> B-Tree index.

They're not crash-safe because they don't have any WAL support, and
WAL-based replication doesn't work for the same reason. But I think
the bit about not being transaction-safe is nonsense ...

regards, tom lane