On 10/20/2015 11:28 PM, Simon Riggs wrote:
On 20 October 2015 at 16:48, Tomas Vondra <tomas.von...@2ndquadrant.com
<mailto:tomas.von...@2ndquadrant.com>> wrote:
>> On 10/20/2015 09:11 PM, Tom Lane wrote:
Can't we just insist that there be only one statistics declaration
for a given column list? >>
I would rather not, because I envision preferring different types of
statistics for different types of queries. For example the statistics
discussed in this particular thread only supports equality clauses,
so this restriction would mean we can't also define histogram, we'll
be unable to estimate queries with ranges.
Can we do something like this...
ADD STATISTICS ON (col list) USING (histogram, MFV)
so we have Types/Methods of statistic, rather than specific names for
the statistic entry?
That's how it works now (comparing columns and types of stats), but I
find it awkward. That's why I proposed adding the name.
Since this command doesn't actually ADD the statistics, it just creates
a specification used by the next ANALYZE, it would seem better to use a
different keyword than ADD, perhaps DECLARE STATISTICS ON... and DROP
STATISTICS ON
Maybe, although we should not use DROP with DECLARE. Not only DROP has
the same issue with name as ADD, but I think it's a good practice to
commands "paired" ADD-DROP and DECLARE-X?
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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