Re: Improving count(*) - Mailing list pgsql-hackers

From Tino Wildenhain
Subject Re: Improving count(*)
Date
Msg-id 437DBFA5.4050208@wildenhain.de
Whole thread Raw
In response to Re: Improving count(*)  ("Zeugswetter Andreas DCP SD" <ZeugswetterA@spardat.at>)
List pgsql-hackers
Zeugswetter Andreas DCP SD schrieb:
>>>Since that costs, I guess I would make it optional and combine it
> 
> with 
> 
>>>materialized views that are automatically used at runtime, and can
> 
> at 
> 
>>>the same time answer other aggregates or aggregates for groups.
>>>create materialized view xx_agg enable query rewrite as select 
>>>count(*), sum (col1) from xx [group by col2];
>>>
>>
>>I wonder how many times you really need a count(*) w/o where clause.
>>If I understand you correctly you are trying to optimize just this one
> 
> case?
> 
> I guess you have not read to the end. A materialized view with a group
> by 
> as indicated in the example is able to answer all sorts of queries
> with or without where clauses ( e.g. ... where col2 = 'x').

But wouldn't that mean I need a materialized view (does we have
that now or do I need to play the usual games with triggers?)
for every possible where condition?


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