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Re: Why we lost Uber as a user

Jim Nasby <jim.nasby@bluetreble.com>

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From: Jim Nasby <Jim.Nasby@BlueTreble.com>
To: Alex Ignatov <a.ignatov@postgrespro.ru>, Vladimir Sitnikov <sitnikov.vladimir@gmail.com>, Josh Berkus <josh@agliodbs.com>, Robert Haas <robertmhaas@gmail.com>
Cc: "Joshua D. Drake" <jd@commandprompt.com>, Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-07-29T14:18:10Z
Lists: pgsql-hackers 
On 7/28/16 10:05 AM, Alex Ignatov wrote:
>> Just curious: what if PostgreSQL supported index that stores "primary
>> key" (or unique key) instead of tids?
>
> You mean IOT like Oracle have?

IIRC, IOT either stores the table in index order, which is something 
different.

What Alex is proposing is an index method that stores a datum instead of 
a ctid. You would then use that datum to probe a different index to get 
the ctid. Or put simply, you have a PK index that contains ctid's, and a 
bunch of other indexes that contain a PK value instead of ctid's.

I think it's an idea worth pursuing, but I don't see how you can make it 
work with our MVCC system unless we drop the aversion to scanning back 
into an index as part of an update.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)   mobile: 512-569-9461

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  1. Advance backend's advertised xmin more aggressively.

  2. Improve snapshot manager by keeping explicit track of snapshots.