Re: jsonb format is pessimal for toast compression

From: Hannu Krosing <hannu(at)2ndQuadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org
Cc: Larry White <ljw1001(at)gmail(dot)com>
Subject: Re: jsonb format is pessimal for toast compression
Date: 2014-08-08 19:50:39
Message-ID: 53E52A0F.2030605@2ndQuadrant.com
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On 08/08/2014 06:17 AM, Tom Lane wrote:
> I looked into the issue reported in bug #11109. The problem appears to be
> that jsonb's on-disk format is designed in such a way that the leading
> portion of any JSON array or object will be fairly incompressible, because
> it consists mostly of a strictly-increasing series of integer offsets.
How hard and how expensive would it be to teach pg_lzcompress to
apply a delta filter on suitable data ?

So that instead of integers their deltas will be fed to the "real"
compressor

--
Hannu Krosing
PostgreSQL Consultant
Performance, Scalability and High Availability
2ndQuadrant Nordic OÜ

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