Re: Postgres and multiple updates in one statement

On Mon, Jul 27, 2009 at 2:10 AM, Jamie
Lawrence-Jenner<jamie.jenner@autovhc.co.uk> wrote:
> Hi there
>
> We have a function which runs a set of update clauses and we are considering
> putting all the update clauses into one statement.
>
> I would like to understand how postgres handles multiple updates. If we were
> to send 5 update statements in one sql statement to the db would it:
>
> Do 5 passes on the table, on each pass, retrieve the id then update the row
>
> Do 1 pass to retrieve the 5 primary keys, then update all rows in parallel

I would do 5 passes.  Better to have one update statement to reduce bloat.