On Wed, 2005-05-25 at 10:41, Tim Vadnais wrote:

> >> Why does Postgres perform an update on the table even 
> >> if no data changes?
> >> Can I circumvent this behaviour of Postgres?
> >>
> Hi All,
> 
> Can someone please address this aspect of Sebastian's email?  I, too, am
> interested in the response.
> 

Actually, I believe it was addressed by Tom, when he said that it would
be more costly to check every single update to see if there WAS a change
before applying it than to just apply the changes every time.

I concur.  Can you imagine slowing down ALL updates by 5% or something
like that just to prevent the rare case where an update didn't actually
change a value?

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TIP 9: the planner will ignore your desire to choose an index scan if your
      joining column's datatypes do not match

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