Re: benchmarking the query planner

On Thu, 2008-12-11 at 13:09 -0500, Tom Lane wrote:

> On the whole I think we have some evidence here to say that upping the
> default value of default_stats_target to 100 wouldn't be out of line,
> but 1000 definitely is.  Comments?

Sounds good to me.

I would like it even more if there was a data type specific default.
Currently we have a special case for boolean, but that's it. TPC allows
for different defaults for different types (but that's not my only
reason). That would allow us to set it lower for long text strings and
floats and potentially higher for things like smallint, which is less
likely as a join target. 

Would be great if we could set the default_stats_target for all columns
in a table with a single ALTER TABLE statement, rather than setting it
for every column individually.

And I would like it even more if the sample size increased according to
table size, since that makes ndistinct values fairly random for large
tables.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support