Re: [HACKERS] Custom compression methods

From: Chapman Flack <chap(at)anastigmatix(dot)net>
To: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: [HACKERS] Custom compression methods
Date: 2017-12-12 22:09:58
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On 12/12/2017 04:33 PM, Robert Haas wrote:

> you want to upgrade your existing tables to use lz4 rather than pglz,
> you can change the compression option for those columns to COMPRESS
> lz4 PRESERVE pglz if you want to do it incrementally or just COMPRESS

This is a thread I've only been following peripherally, so forgive
a question that's probably covered somewhere upthread: how will this
be done? Surely not with compression-type bits in each tuple? By
remembering a txid where the compression was changed, and the former
algorithm for older txids?


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