MySQL Forums
Forum List  »  Performance

Advanced Search
New Topic

Re: Simple query seems to be ignoring date index
Posted by: Øystein Grøvlen
Date: November 01, 2013 02:47AM

Hi Greg,

How is the data ordered within the table? Could it be that it is more or less clustered on sym value? If so, that could explain why it is sym look-up is quicker than look-up on date.

Which version of MySQL are you using? MySQL 5.6 supports disk-sweep multi-range read (DS-MRR) which is a mechanism to re-arrange accesses to table to make it more sequential. You may have to set optimizer_switch='mrr_cost_based=off' to force DS-MRR in that case. Also, increasing the value of read_rnd_buffer_size is probably necessary to get the full benefit of DS-MRR.

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway

Navigate: Previous Message• Next Message
Options: Reply• Quote


Subject
Views
Written By
Posted
Simple query seems to be ignoring date index
2894
Greg Schubin
October 26, 2013 11:38AM
Re: Simple query seems to be ignoring date index
1047
Greg Schubin
October 28, 2013 08:56AM
Re: Simple query seems to be ignoring date index
973
Rick James
October 28, 2013 09:35PM
Re: Simple query seems to be ignoring date index
987
Greg Schubin
October 29, 2013 10:19AM
Re: Simple query seems to be ignoring date index
1074
Rick James
October 30, 2013 07:47PM
Re: Simple query seems to be ignoring date index
1039
Greg Schubin
October 31, 2013 12:23AM
Re: Simple query seems to be ignoring date index
1002
Øystein Grøvlen
November 01, 2013 02:47AM
Re: Simple query seems to be ignoring date index
1064
Greg Schubin
November 01, 2013 11:20AM
Re: Simple query seems to be ignoring date index
1252
Rick James
November 01, 2013 10:45PM
Re: Simple query seems to be ignoring date index
996
Greg Schubin
November 02, 2013 09:45PM
Re: Simple query seems to be ignoring date index
1048
Rick James
November 02, 2013 09:59PM
Re: Simple query seems to be ignoring date index
1024
Øystein Grøvlen
November 04, 2013 04:55AM


Sorry, you can't reply to this topic. It has been closed.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.