Re: Bloated pg_shdepend_depender_index

On 3/23/06, Alvaro Herrera <alvherre(at)commandprompt(dot)com> wrote:
> Gregory Maxwell wrote:
>
> > I recently noticed that this database has grown to a huge size. ...
> > Which I found to be somewhat odd because none of the tables have more
> > than around 1000 rows. I hadn't been vacuuming because I didn't
> > think that anything would ever be deleted.... so I performed a vacuum
> > full... but no luck, it was still about 6.4GB.
> >
> > With some help of the folks on IRC I discovered...
> > postgres=# select relname, pg_relation_size(oid) FROM pg_class ORDER
> > BY 2 DESC LIMIT 2;
> > relname | pg_relation_size
> > -----------------------------+------------------
> > pg_shdepend_depender_index | 159465472
> > pg_shdepend_reference_index | 97271808
> > (2 rows)
>
> Huh, that's very strange.
>
> The pg_shdepend table is a shared catalog, unlike most other catalogs.
> Still I don't see why would the indexes not shrink. Do pg_authid,
> pg_database, or pg_tablespace show a similar behavior? Is amarok
> creating a lot of temp tables or something? When you did that vacuum
> full, was there a process connected to the same or another database that
> could be holding onto the pg_shdepend table?
>
> I'll have a look at the code, but I thought I might throw that out, just
> in case it rings a bell.

Those were the only two objects impacted. I'm not sure what amarok
does.. a quick glance at the source shows that it does use temp
tables, but I'm not sure how frequently.

When I vacuum fulled nothing else was connected.. I just restarted PG
and vacuumed again.. no obvious change of disk size (still.. 6.4
gigs).. but this changed:

amarokcollection=# select relname, pg_relation_size(oid) FROM
pg_class ORDER BY 2 DESC LIMIT 20;
relname | pg_relation_size
---------------------------------+------------------
pg_attribute_relid_attnam_index | 2881069056
pg_class_relname_nsp_index | 1185890304
pg_attribute_relid_attnum_index | 710565888
pg_depend_depender_index | 451190784
pg_depend_reference_index | 422363136
pg_type_typname_nsp_index | 245293056
pg_class_oid_index | 208420864
pg_shdepend_depender_index | 159465472
pg_shdepend_reference_index | 97271808
pg_constraint_conname_nsp_index | 55107584
pg_index_indrelid_index | 50774016
pg_index_indexrelid_index | 50774016
pg_type_oid_index | 44400640
pg_attrdef_adrelid_adnum_index | 15761408
pg_constraint_conrelid_index | 15728640
pg_constraint_oid_index | 15728640
pg_attrdef_oid_index | 12541952
pg_constraint_contypid_index | 7618560
statistics_url_key | 2113536
url_stats | 2105344

The old output was:
postgres=# select relname, pg_relation_size(oid) FROM pg_class ORDER
BY 2 DESC LIMIT 10; relname |
pg_relation_size
---------------------------------+------------------
pg_shdepend_depender_index | 159465472
pg_shdepend_reference_index | 97271808
pg_proc | 352256
pg_proc_proname_args_nsp_index | 344064
pg_depend | 237568
pg_attribute_relid_attnam_index | 204800
pg_attribute | 204800
pg_depend_reference_index | 172032
pg_depend_depender_index | 155648
pg_statistic | 131072
(10 rows)

I'm at your disposal on this.. it's weird.