Re: Let's drop two obsolete features which are bear-traps for novices

On 2014-11-01 10:18:03 -0700, Josh Berkus wrote:
> On 10/31/2014 03:07 PM, Tom Lane wrote:
> > I don't care one way or the other about the money type, but I will defend
> > hash indexes, especially seeing that we've already added a pretty
> > in-your-face warning as of 9.5:
> > 
> > regression=# create table foo(f1 int);
> > CREATE TABLE
> > regression=# create index on foo using hash (f1);
> > WARNING:  hash indexes are not WAL-logged and their use is discouraged
> > CREATE INDEX
> 
> Yes, and I'm arguing that is the wrong decision.  If hash indexes are
> "discouraged", then they shouldn't be in core in the first place.

Last time we discussed it there were people (IIRC Andrew was one of
them) commenting that they use hash indexes *precisely* because they're
not WAL logged and that they can live with the dangers that creates. I
don't think that's sufficient justification for introducing the feature
at all. But it's nothing new that removing a feature has to fit quite
different criteria than adding one.

So, by that argument we could remove hash indexes once we have unlogged
indexes on logged tables. But then there's no need to remove them
anymore...

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services