Re: Does having a NULL column automatically exclude the table from the tupleDesc cache?

From: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>
To: Ryan Murphy <ryanfmurphy(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Does having a NULL column automatically exclude the table from the tupleDesc cache?
Date: 2017-02-17 19:03:19
Message-ID: a8c86d85-0117-ce74-5348-5ed6d17603b6@BlueTreble.com
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On 2/15/17 1:37 PM, Ryan Murphy wrote:
>
> attcacheoff can only be set positive for fields preceding any varlena
> (typlen<0, but including the first such) or nullable values. I don't
> know how much faster it is with the cache; you can measure it if your
> curiosity is strong enough -- just set the first column to nullable.
>
>
> Thanks! Maybe I'll do some benchmarks.

You'll probably want to do those at a C level, bypassing the executor. I
would guess that executor overhead will completely swamp the effect of
the cache in most cases.
--
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)

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