I had thought that the Creation of the Index would do something
equivalent to Analyze. I tried Analyze Verbose and it improved
the scanner's ability to predict when an index would be useful.
Last week, I asked about visualizing B-tree "coverage". I think
I meant "Can I see the histograms that Analyze creates?"
Are they available anywhere? The docs mention them (bins) and I
was hoping Analyze Verbose would show them to me.
TJ
Tom Lane wrote:
> "TJ O'Donnell" <tjo@acm.org> writes:
>
>>This I don't get. Why is an index scan not used? Isn't an index supposed
>>to help when using > < >= <= too?
>>Explain Analyze Select count(smiles) from structure where _c >= 30
>>Aggregate (cost=196033.74..196033.74 rows=1 width=32) (actual time=42133.432..42133.434 rows=1
>>loops=1)
>> -> Seq Scan on structure (cost=0.00..191619.56 rows=1765669 width=32) (actual
>>time=8050.437..42117.062 rows=1569 loops=1)
>> Filter: (_c >= 30)
>
>
> Have you ANALYZEd the table lately? That rowcount estimate is off by
> about three orders of magnitude :-(
>
> regards, tom lane
