Horton

Re: Compressed TOAST Slicing

Daniel Verite <daniel@manitou-mail.org>

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From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Paul Ramsey" <pramsey@cleverelephant.ca>
Cc: "Simon Riggs" <simon@2ndquadrant.com>,rafia.sabih@enterprisedb.com,"Tom Lane" <tgl@sss.pgh.pa.us>,"Stephen Frost" <sfrost@snowman.net>,"PostgreSQL Hackers" <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-20T19:12:18Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add support for partial TOAST decompression

  2. Remove remaining hard-wired OID references in the initial catalog data.

  3. Rephrase references to "time qualification".

	Paul Ramsey wrote:

> > text_starts_with(arg1,arg2) in varlena.c does a full decompression
> > of  arg1 when it could limit itself to the length of the smaller arg2:
> 
> Nice catch, I didn't find that one as it's not user visible, seems to
> be only called in spgist (!!)

It's also exposed in SQL since v11, as 
  starts_with(string,prefix) returns bool
and as an operator:
  text ^@ text
I guess it's meant to be more efficient than (string LIKE prefix||'%')
or strpos(string,prefix)=1, and it will be even more so if we can
avoid some amount of decompression :)


Best regards,
-- 
Daniel Vérité
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Twitter: @DanielVerite