Re: reducing statistics write overhead

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.