Timeline for INNER JOIN making COUNT(*) slow
Current License: CC BY-SA 3.0
13 events
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| Jan 15, 2018 at 17:14 | comment | added | Lennart - Slava Ukraini |
Is the performance affected if you use a non-nullable column from messages in COUNT? I.e. SELECT COUNT(messages.message_id) FROM messages JOIN .... It should be possible for the optimizer to eliminate the join, check if that helps.
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| Jan 15, 2018 at 14:43 | history | edited | Aaron Bertrand |
edited tags
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| Aug 13, 2012 at 16:25 | vote | accept | Darthtong | ||
| Aug 13, 2012 at 15:46 | comment | added | Jean-Bernard Lagorce | I don't see the point of the join, unless you plan to add filtering on the users table (an index on messages.user_id should help then would ) By now, it seems that a simple select count(message_id) from messages should do the trick | |
| Aug 13, 2012 at 15:39 | history | edited | Aaron Bertrand | CC BY-SA 3.0 |
Removed tag from title (we know it's SQL Server).
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| Aug 13, 2012 at 15:36 | history | migrated | from stackoverflow.com (revisions) | ||
| Aug 13, 2012 at 15:36 | answer | added | podiluska | timeline score: -1 | |
| Aug 13, 2012 at 15:34 | comment | added | Martin Smith |
Please provide the CREATE TABLE statements including indexes and the execution plan.
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| Aug 13, 2012 at 15:34 | answer | added | Clinton Ward | timeline score: -1 | |
| Aug 13, 2012 at 15:34 | answer | added | Aaron Bertrand | timeline score: 5 | |
| Aug 13, 2012 at 15:32 | comment | added | Darthtong | No there will always be a match | |
| Aug 13, 2012 at 15:31 | comment | added | Aaron Bertrand | Do you have any rows in messages where user_id won't be in users? (e.g. is the foreign key nullable) | |
| Aug 13, 2012 at 15:30 | history | asked | Darthtong | CC BY-SA 3.0 |