Re: [HACKERS] Binary search in fmgr_isbuiltin() is a bottleneck. - Mailing list pgsql-hackers

From Robert Haas
Subject Re: [HACKERS] Binary search in fmgr_isbuiltin() is a bottleneck.
Date
Msg-id CA+TgmoaAWfFMa6XQeOjXevjE_31E_aZm352WsqvJ4Lq1szdrhQ@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] Binary search in fmgr_isbuiltin() is a bottleneck.  (Andres Freund <andres@anarazel.de>)
Responses Re: [HACKERS] Binary search in fmgr_isbuiltin() is a bottleneck.  (Andres Freund <andres@anarazel.de>)
List pgsql-hackers
On Wed, Sep 27, 2017 at 1:00 PM, Andres Freund <andres@anarazel.de> wrote:
> We could relatively easily move it to be once-per-postmaster start for
> !EXEC_BACKEND builds. Constantly doing expensive binary searches is also
> pretty brute force ;)

I think one useful way to look at it might be -

How many fmgr searches does a backend need to do in order to make up
for the time spent building the hash table?

How many fmgr searches, if any, do we do during backend startup as a
matter of course?

If we're going to make up the time that it takes to build the hash
table by the time the user runs a handful of queries, there's really
no point in stressing about this.  The use case where somebody
repeatedly connects and disconnects without running any significant
number of real queries is not an important one.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

pgsql-hackers by date:

Previous
From: Andres Freund
Date:
Subject: Re: [HACKERS] SendRowDescriptionMessage() is slow for queries with alot of columns
Next
From: Alexander Korotkov
Date:
Subject: Re: [HACKERS] [PATCH]make pg_rewind to not copy useless WAL files