Thread: hash indexes and HS was:(Re: [HACKERS] testing hot standby)

On Mon, Apr 12, 2010 at 1:23 AM, Jaime Casanova
<jcasanov@systemguards.com.ec> wrote:
>
> another point, what happened with this:
> http://archives.postgresql.org/message-id/1229549172.4793.105.camel@ebony.2ndQuadrant?
> Obviously we still have the problem with hash indexes, and in that
> thread Tom advice was just to document the issue and while that could
> be fine at least we should be emitting better messages, consider this
> one that i got on the standby server (where 4658650 is the oid of a
> hash index):
> """
> mic=# explain analyze select * from tt1 where col1 = 5000;
> ERROR:  could not read block 0 in file "base/21958/4658650": read only
> 0 of 8192 bytes
> """
>

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157

On Tue, 2010-04-13 at 10:41 -0500, Jaime Casanova wrote:
> On Mon, Apr 12, 2010 at 1:23 AM, Jaime Casanova
> <jcasanov@systemguards.com.ec> wrote:
> >
> > another point, what happened with this:
> > http://archives.postgresql.org/message-id/1229549172.4793.105.camel@ebony.2ndQuadrant?
> > Obviously we still have the problem with hash indexes, and in that
> > thread Tom advice was just to document the issue and while that could
> > be fine at least we should be emitting better messages, consider this
> > one that i got on the standby server (where 4658650 is the oid of a
> > hash index):
> > """
> > mic=# explain analyze select * from tt1 where col1 = 5000;
> > ERROR:  could not read block 0 in file "base/21958/4658650": read only
> > 0 of 8192 bytes
> > """

The issue is clearly documented and follows result of discussion.

If we allow scans on hash indexes, there isn't any good way to catch an
ERROR at this point. I'm in favour of applying the patch that would give
a good error message, but not everybody agrees, AFAIK.

-- Simon Riggs           www.2ndQuadrant.com