Simon Riggs wrote:
> On Wed, 2005-09-21 at 15:39 -0400, Tom Lane wrote:
> > Simon Riggs <simon@2ndquadrant.com> writes:
> > > Is it possible that the Release Notes do not fully explain the
> > > Constraint Exclusion feature? Or is it the consensus that it works but
> > > not quite well enough to make a song and dance about yet?
> >
> > I hardly think that the existing constraint-exclusion code is enough for
> > us to claim we "support table partitioning". There's too much grunt
> > work that the DBA still has to do to set up a partitioning arrangement.
>
> So you think the DBA can do partitioning? Good.
>
> Setting up partitioning in Oracle or SQLServer2005 requires lots of
> syntax and multiple commands. There are fewer commands with PostgreSQL
> and they are ISO/ANSI compliant also.
>
> I think there is much still left to do with partitioning, so I would be
> the first to say that this is only the beginning. I know you are wary of
> overstating capabilities; so am I, but it looks like we differ slightly
> on where to draw the line.
>
> On reflection, the only changes I suggest are:
>
> 1) the phrase "This allows for a type of table partitioning" have the
> word "basic" inserted within it to become: "This allows for a basic type
> of table partitioning"
>
> 2) placing CE as a major feature of 8.1 - many people regard it at least
> as highly as other optimizations, though this is subjective based upon
> their application requirements
>
> Suggestion (2) might be seen as some kind of vanity, so having raised
> the issue I'll leave the floor open to others to agree or not.
Having heard no comments, I have moved this item up into the main
features section of the release notes, and reworded it:
Improve performance for partitioned tables (Simon)
The new constraint_exclusion configuration parameter avoids lookups on child tables where constraints
indicate that no matching rows exist in the child table.
This allows for a basic type of table partitioning. If child tables store separate key ranges and this
is enforced using appropriate "CHECK" constraints, the optimizer will skip child table accesses when the
constraint guarantees no matching rows exist in the child table.
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