Re: Transactions vs speed.

Alfred Perlstein wrote:
>
> * mlw <markw(at)mohawksoft(dot)com> [010113 17:19] wrote:
> > I have a question about Postgres:
> >
> > Take this update:
> > update table set field = 'X' ;
> >
> >
> > This is a very expensive function when the table has millions of rows,
> > it takes over an hour. If I dump the database, and process the data with
> > perl, then reload the data, it takes minutes. Most of the time is used
> > creating indexes.
> >
> > I am not asking for a feature, I am just musing.
>
> Well you really haven't said if you've tuned your database at all, the
> way postgresql ships by default it doesn't use a very large shared memory
> segment, also all the writing (at least in 7.0.x) is done syncronously.
>
> There's a boatload of email out there that explains various ways to tune
> the system. Here's some of the flags that I use:
>
> -B 32768 # uses over 300megs of shared memory
> -o "-F" # tells database not to call fsync on each update

I have a good number of buffers (Not 32768, but a few), I have the "-F"
option.

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