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Re: A thought on Index Organized Tables

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Gokulakannan Somasundaram <gokul007(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>, Greg Stark <gsstark(at)mit(dot)edu>, Karl Schnaitter <karlsch(at)gmail(dot)com>
Subject: Re: A thought on Index Organized Tables
Date: 2010-02-28 15:47:54
Message-ID: 8512.1267372074@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Gokulakannan Somasundaram <gokul007(at)gmail(dot)com> writes:
> a) We are already going from table to index to do unique checks. This is the
> same thing, which we will do to go and update the snapshot in the indexes.

No, it is not the same thing.  Updating index snapshots requires being
able to *re-find* a previously made index entry for the current row.
And it has to be done 100% reliably.  The worst that happens if an index
entry is not found when it should be during a uniqueness check is that
the uniqueness constraint is not enforced properly; which is bad but it
doesn't lead to internally-inconsistent data structures.

> b) The way, it should work would be to have a check on whether the operator
> is broken / function is volatile and put the onus on the user to make sure
> that they are updated correctly.

Pretending the problem doesn't exist doesn't make it go away ...

			regards, tom lane

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