help interpreting "explain analyze" output - Mailing list pgsql-general

From David Rysdam
Subject help interpreting "explain analyze" output
Date
Msg-id 87bo1784av.fsf@loud.llan.ll.mit.edu
Whole thread Raw
Responses Re: help interpreting "explain analyze" output
Re: help interpreting "explain analyze" output
List pgsql-general
I'm not really looking for information on how to speed this query
up. I'm just trying to interpret the output enough to tell me which step
is slow:

   Seq Scan on mags  (cost=0.00..187700750.56  rows=47476  width=4) (actual time=3004851.889..3004851.889  rows=0
loops=1)
      Filter:  ((signum IS NOT NULL) AND (NOT (SubPlan 1)))
      SubPlan 1
        -> Materialize  (cost=0.00..3713.93  rows=95862  width=4) (actual time=0.011..16.145  rows=48139  loops=94951)
               -> Seq Scan on sigs (cost=0.00..2906.62 rows=95862 width=4) (actual time=0.010..674.201  rows=95862
loops=1)
   Total runtime: 3004852.005 ms

It looks like the inner seq scan takes 674ms, then the materialize takes
an additional 16ms? Or is that 16ms * 94951? Or 674 * 94951?

And the outer seq scan takes 3004851-3004851 = 0ms?



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