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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject territory-based collations and optimizations for the LIKE operator
Date Fri, 22 Aug 2008 17:16:55 GMT
According to the Developer's Guide section titled "Character-based 
collation in Derby", the LIKE operator behaves differently than the = 
operator. That is, if you are using a territory-based collation, two 
strings might = one another but not be LIKE one another (and vice-versa).

In the meantime, according to the section in the Tuning Guide titled 
"Character string beginning with constant", LIKE expressions which begin 
with a constant (followed by a wildcard) can be transformed into 
indexable expressions involving the ">=" and "<" operators.

To my muddled understanding, it seems that one of the following occurs:

1) The LIKE optimizations are disabled if you are using territory-based 
collation

or

2) a LIKE expression may return different results depending on your 
indexes and/or the presence of trailing wildcards in your LIKE expression.

(1) seems like a performance issue which needs to be documented. (2) 
seems like a correctness problem. What is the behavior that we expect?

Thanks,
-Rick

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