Damn. Anyone know why the heck FB won't use an index in a join with 'starting with'? FWIW, I ran the natural part of the query to generate a bunch of "starting with 'xyx' or" and appended them to query the other table. Luckily I didn't hit any query limits.
-----Original Message----- From: firebird-support@yahoogroups.com [mailto:firebird-support@yahoogroups.com] On Behalf Of Svein Erling Tysvær Sent: Monday, April 09, 2012 3:29 PM To: firebird-support@yahoogroups.com Subject: SV: [firebird-support] No index used for join on 'starting with' >>This query uses natural for both tables, when I expected it to use an >>index for the join. >> >>select * >>from table1 t1 >>join table2 t2 on t2.indexed_char14 starting with t1.indexed_char10 >>where t1.unindex_varchar containing 'foo' >> >>This uses an index, so the optimizer knows about it. >> >>select * >>from table2 t2 >>where t2.indexed_char14 starting with 'bar' >> >>How can I get the optimizer to use the index for the join? > >Anyone? Without any indexes, I won't live to see this complete. Not a good suggestion (my simplified understanding of how Firebird JOINs tables, may not be appropriate when STARTING WITH is part of the JOIN, so I've no clue how to force that index), but I can think of two possible solutions: a) An expression index and join table2 t2 on substring(t2.indexed_char14 from 1 for 10) = t1.indexed_char10 b) Add a calculated field t2.indexed_char10 that you index and then change your JOIN to: join table2 t2 on t2.indexed_char10 = t1.indexed_char10 Sorry for not having any better suggestions, Set Disclaimer: This message (including attachments) is confidential and may be privileged. If you have received it by mistake please notify the sender by return e-mail and delete this message from your system. Any unauthorized use or dissemination of this message in whole or in part is strictly prohibited. Please note that e-mails are susceptible to change. RxStrategies, Inc. shall not be liable for the improper or incomplete transmission of the information contained in this communication or for any delay in its receipt or damage to your system. RxStrategies, Inc. does not guarantee that the integrity of this communication has been maintained nor that this communication is free from viruses, interceptions or interference.
