| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Viktor Rosenfeld <rosenfel(at)informatik(dot)hu-berlin(dot)de> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Indexes not used in DELETE |
| Date: | 2009-05-07 23:06:56 |
| Message-ID: | 6572.1241737616@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Viktor Rosenfeld <rosenfel(at)informatik(dot)hu-berlin(dot)de> writes:
> -> Seq Scan on corpus toplevel (cost=0.00..1.39 rows=1 width=54)
> Filter: (top_level AND (id = 25::numeric))
> Specifically, I'm wondering why the innermost scan on corpus
> (toplevel) does not use the index idx_corpus__toplevel
The cost estimate indicates that there are so few rows in corpus
that an indexscan would be a waste of time.
> and why the
> join between corpus (toplevel) and corpus (child) is not a merge join
> using the index corpus_pre_key to access the child table.
Same answer. Populate the table and the plan will change.
regards, tom lane
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