Re: Trying to get postgres to use an index

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Тема Re: Trying to get postgres to use an index
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Msg-id 1726.12.134.204.65.1099781414.squirrel@mail.linkify.com
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Ответ на Re: Trying to get postgres to use an index  (Joel Stevenson <joelstevenson@mac.com>)
Ответы Re: Trying to get postgres to use an index  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-general
> I'm not a SQL guru by any stretch but would a
> constrained sub-select be appropriate here?

> Well, you're joining the entire two tables, so yes, the seq scan might
> be faster.

My mistake!  When composing the email to state the problem, I accidentally
gave a wrong version of the join query.

Here is the corrected version, which still has the sequential scan...

explain  select notificationID from NOTIFICATION n, ITEM i where n.itemID
= i.itemID and i.projectID = 12;
                                            QUERY PLAN
---------------------------------------------------------------------------
-----------------------
 Hash Join  (cost=2237.54..15382.32 rows=271 width=44)
   Hash Cond: ("outer".itemid = "inner".itemid)
   ->  Seq Scan on notification n  (cost=0.00..12023.71 rows=223671
width=48)
   ->  Hash  (cost=2235.31..2235.31 rows=895 width=4)
         ->  Index Scan using item_ix_item_4_idx on item i
         (cost=0.00..2235.31 rows=895width=4)
               Index Cond: (projectid = 12)





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