Re: Autovacuum on partitioned table

Hello,

> Besides the complexity of
> getting that infrastructure in place, an important question is whether
> the current system of applying threshold and scale factor to
> changes_since_analyze should be used as-is for inheritance parents
> (partitioned tables), because if users set those parameters similarly
> to for regular tables, autovacuum might analyze partitioned tables
> more than necessary.  We'll either need a different formula, or some
> commentary in the documentation about how partitioned tables might
> need different setting, or maybe both.
>
I'm not sure but I think we need new autovacuum parameters for
partitioned tables (autovacuum, autovacuum_analyze_threshold,
autovacuum_analyze_scale_factor) because whether it's necessary
to run autovacuum on partitioned tables will depend on users.
What do you think?

> How are you going to track changes_since_analyze of partitioned table?
> It's just an idea but we can accumulate changes_since_analyze of
> partitioned table by adding child tables's value after analyzing each
> child table. And compare the partitioned tables value to the threshold
> that is computed by (autovacuum_analyze_threshold  + total rows
> including all child tables * autovacuum_analyze_scale_factor).
>
The idea Sawada-san mentioned is similar to mine.  Also, for tracking
changes_since_analyze, we have to make partitioned table's statistics.
To do that, we can invent a new PgStat_StatPartitionedTabEntry based
on PgStat_StatTabEntry.  Through talking with Amit, I think the new structure
needs the following members:

tableid
changes_since_analyze
analyze_timestamp
analyze_count
autovac_analyze_timestamp
autovac_analyze_count

Vacuum doesn't run on partitioned tables, so I think members related to
(auto) vacuum need not be contained in the structure.

I'm still writing a patch.  I'll send it this week.
-- 
Best regards,
Yuzuko Hosoya
NTT Open Source Software Center