Re: A thought on Index Organized Tables

Simon Riggs wrote:
> On Mon, 2010-02-22 at 08:51 +0200, Heikki Linnakangas wrote:
>> Gokulakannan Somasundaram wrote:
>
>>> May i get a little clarification on this issue? Will we be supporting
>>> the IOT feature in postgres in future?
>> What seems like the best path to achieve the kind of performance
>> benefits that IOTs offer is allowing index-only-scans using the
>> visibility map.
>
> I don't agree with that. Could you explain why you think that would be
> the case? It would be a shame to have everybody think you can solve a
> problem if it turned out not to be the case.

I'm thinking of a scan based on the index key. With an
index-organised-table, you can skip the heap access because the heap and
the index are the same structure. An index-only-scan likewise allows you
to skip the heap access.

I grant you that an index-organised-table can have other benefits, like
reduced disk space usage (which is good cache efficiency), or less
random I/O required for updates.

The question was if PostgreSQL will be supporting index-organised-tables
in the future. The answer is "not in the foreseeable future". No-one has
come up with a plausible plan for how to do it, and no-one working on it
at the moment.

I don't want to discourage thinking about pie-in-the-sky features.
There's many tricks like column-oriented storage, compression,
index-organised-tables etc. that would be nice to have. Whether any
particular feature is worthwhile in the end, the devil is in the details.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com