| From: | "Daniel Verite" <daniel(at)manitou-mail(dot)org> |
|---|---|
| To: | "Paul Ramsey" <pramsey(at)cleverelephant(dot)ca> |
| Cc: | "Simon Riggs" <simon(at)2ndquadrant(dot)com>,rafia(dot)sabih(at)enterprisedb(dot)com,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Stephen Frost" <sfrost(at)snowman(dot)net>,"PostgreSQL Hackers" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Compressed TOAST Slicing |
| Date: | 2019-02-20 19:12:18 |
| Message-ID: | eee6e817-29bd-451f-8105-2d4bb3e2aedc@manitou-mail.org |
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| Lists: | pgsql-hackers |
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
PostgreSQL-powered mailer: http://www.manitou-mail.org
Twitter: @DanielVerite
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