| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Melo <al_nunes(at)atua(dot)com(dot)br> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Tables used in query not listed in EXPLAIN |
| Date: | 2014-10-16 20:04:28 |
| Message-ID: | 8909.1413489868@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Alvaro Melo <al_nunes(at)atua(dot)com(dot)br> writes:
> I have a peculiar situation here. I'm optimizing some queries and I
> noticed that EXPLAIN doesn't always show the tables involved in the
> query. Below is a little example, but I have other examples with longer
> queries. Note that the tables tabela_documento_fiscal and pessoa aren't
> considered on it's output. Am I missing someting or it might be a bug?
It looks to me like it's optimizing away the left joins, presumably
on the grounds that they join to a unique key so there can't be more
than one matching row --- and this query has no need to know exactly
which row, if any, matches.
regards, tom lane
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