Re: hash index on unlogged tables doesn't behave as expected

On Thu, Sep 21, 2017 at 4:14 PM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
> postgres=# create table test (id int primary key, v text);
> postgres=# create index on test using hash (id);
> WARNING: hash indexes are not WAL-logged and their use is discouraged
>
> But not for for unlogged tables.
>
> postgres=# create unlogged table test (id int primary key, v text);
> postgres=# create index on test using hash (id);
> postgres=# (no warning)
>
> And fails on promotion in the same way.
>
> postgres=# select * from test;
> ERROR: could not open file "base/13324/16446": No such file or directory
>
> indexcmds(dot)c(at)965:503
>> if (strcmp(accessMethodName, "hash") == 0 &&
>> RelationNeedsWAL(rel))
>> ereport(WARNING,
>> (errmsg("hash indexes are not WAL-logged and their use is discouraged")));
>
> Using !RelationUsesLocalBuffers instead fixes that and the
> attached patch is for 9.6. I'm a bit unconfident on the usage of
> logical meaning of the macro but what it does fits there.
>

I think giving an error message like "hash indexes are not WAL-logged
and .." for unlogged tables doesn't seem like a good behavior.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com