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Re: Inheritance efficiency

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Vincenzo Romano <vincenzo(dot)romano(at)notorand(dot)it>, David Fetter <david(at)fetter(dot)org>, PostgreSQL General <pgsql-general(at)postgresql(dot)org>
Subject: Re: Inheritance efficiency
Date: 2010-04-30 20:48:54
Message-ID: 201004302048.o3UKmsO25945@momjian.us (view raw or flat)
Thread:
Lists: pgsql-general
Alvaro Herrera wrote:
> Vincenzo Romano wrote:
> 
> > This is not enterprise grade.
> 
> "Enterprise grade" is nothing but a buzzword.  Oh, it's also a moving
> target.  We've been not enterprise grade for years, always one feature
> behind (and strangely, the one lacking feature is always the one of
> interest to the complainant).

We do have this enhancement coming in Postgres 9.0:

	 Add an index on pg_inherits.inhparent, and use it to avoid seqscans
	 in find_inheritance_children().  This is a complete no-op in databases
	 without any inheritance.  In databases where there are just a few
	 entries in pg_inherits, it could conceivably be a small loss.  However,
	 in databases with many inheritance parents, it can be a big win.

However, I don't think this going to help a lot for partitioning because
the cost is mostly checking the CHECK constraints, not finding the
table's children.

Like all Postgres missing features, we just need someone with time to
volunteer to research and fix it.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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