| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | "Greg Stark" <gsstark(at)mit(dot)edu>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, heikki(dot)linnakangas(at)enterprisedb(dot)com, "Gokulakannan Somasundaram" <gokul007(at)gmail(dot)com>, "Karl Schnaitter" <karlsch(at)gmail(dot)com>, "pgsql-hackers list" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: A thought on Index Organized Tables |
| Date: | 2010-02-24 17:46:06 |
| Message-ID: | 20862.1267033566@sss.pgh.pa.us |
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"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Greg Stark <gsstark(at)mit(dot)edu> wrote:
>> That doesn't work because when you split an index page any
>> sequential scan in progress will either see the same tuples twice
>> or will miss some tuples depending on where the new page is
>> allocated. Vacuum has a clever trick for solving this but it
>> doesn't work for arbitrarily many concurrent scans.
> It sounds like you're asserting that Index Scan nodes are inherently
> unreliable, so I must be misunderstanding you.
We handle splits in a manner that insures that concurrent index-order
scans remain consistent. I'm not sure that it's possible to scale that
to ensure that both index-order and physical-order scans would remain
consistent. It might be soluble but it's certainly something to worry
about.
regards, tom lane
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