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Re: Where the advice to use DBI bind parameters can go wrong (long)by mpeppler (Vicar) |
on Jun 14, 2002 at 22:58 UTC ( [id://174741]=note: print w/replies, xml ) | Need Help?? |
Interesting observation. For Sybase the optimizer determines index usage when the query is run the first time. So if the first request only has a trailing '%' and the column has an index it will be used. A subsequent query with a leading '%' won't be incorrect - the optimizer detects the leading '%' and while it uses the index it will look at all the values for a match. However, if the first query has a leading '%' then you will get a table scan each time. I ran the following:
The showplan output shows that the index is used, but the stats IO shows that the second execute() call does a lot more work: vs.
FWIW :-) Michael
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