i) provide better accuracy than the last ANALYZE ii) make it behave like an aggregate
So I wanted to be able to use estimated_count as you would use count, i.e:
SELECT estimated_count() FROM rel
returns 1 row, whereas the scalar function :
SELECT estimated_count(rel) FROM rel
returns the result as many times as there are rows in rel - of course you would use
SELECT estimated_count(rel)
but hopefully you see what I mean!
BTW, the scalar function is pretty simple to achieve - here is a basic example that ignores schema qualifiers:
CREATE FUNCTION estimated_count(text) RETURNS real AS ' SELECT reltuples FROM pg_class WHERE relname = $1; ' LANGUAGE SQL;
cheers
Mark
Simon Riggs wrote:
Why not implement estimated_count as a dictionary lookup, directly using the value recorded there by the analyze? That would be the easiest way to reuse existing code and give you access to many previously calculated values.
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