Re: Very slow queries on 8.1

Tom Lane wrote:

>David Rysdam <drysdam(at)ll(dot)mit(dot)edu> writes:
>
>
>>Right now, I'm working on a test case that involves a table with ~360k
>>rows called "nb.sigs". My sample query is:
>>select * from nb.sigs where signum > 250000
>>With no index, explain says this query costs 11341. After CREATE INDEX
>>on the signum field, along with an ANALYZE for nb.sigs, the query costs
>>3456 and takes around 4 seconds to return the first row. This seems
>>extremely slow to me, but I can't figure out what I might be doing
>>wrong. Any ideas?
>>
>>
>
>How many rows does that actually return, and what client interface are
>you fetching it with? libpq, at least, likes to fetch the entire query
>result before it gives it to you --- so you're talking about 4 sec to
>get all the rows, not only the first one. That might be reasonable if
>you're fetching 100k rows via an indexscan...
>
> regards, tom lane
>
>
>
>
Right, it's about 100k rows and it is through libpq (pgadmin in this
case, but my app uses libpq from pgtcl). Is there a way to tell libpq
to not do what it "likes" and do what I need instead? I didn't see
anything in the docs, but I didn't look very hard.