Re: reducing statistics write overhead - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: reducing statistics write overhead
Date
Msg-id 20090122231437.GO4296@alvh.no-ip.org
Whole thread Raw
In response to Re: reducing statistics write overhead  (Euler Taveira de Oliveira <euler@timbira.com>)
Responses Re: reducing statistics write overhead  (Euler Taveira de Oliveira <euler@timbira.com>)
List pgsql-hackers
Euler Taveira de Oliveira escribió:
> Alvaro Herrera escreveu:
> > This could be solved if the workers kept the whole history of tables
> > that they have vacuumed.  Currently we keep only a single table (the one
> > being vacuumed right now).  I proposed writing these history files back
> > when workers were first implemented, but the idea was shot down before
> > flying very far because it was way too complex (the rest of the patch
> > was more than complex enough.)  Maybe we can implement this now.
> > 
> [I don't remember your proposal...] Isn't it just add a circular linked list
> at AutoVacuumShmemStruct? Of course some lock mechanism needs to exist to
> guarantee that we don't write at the same time. The size of this linked list
> would be scale by a startup-time-guc or a reasonable fixed value.

Well, the problem is precisely how to size the list.  I don't like the
idea of keeping an arbitrary number in memory; it adds another
mostly-useless tunable that we'll need to answer questions about for all
eternity.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.


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