Re: [HACKERS] Custom compression methods - Mailing list pgsql-hackers

From Chapman Flack
Subject Re: [HACKERS] Custom compression methods
Date
Msg-id 24d500f8-6c95-03f4-5a1e-d4205dca95d3@anastigmatix.net
Whole thread Raw
In response to Re: [HACKERS] Custom compression methods  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
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?

-Chap


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