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Re^3: In search of an efficient query abstractor

by Corion (Pope)
on Dec 07, 2008 at 15:48 UTC ( #728733=note: print w/replies, xml ) Need Help??

in reply to Re^2: In search of an efficient query abstractor
in thread In search of an efficient query abstractor

Of course you can just do what lex does, but if you use a good character class as the first character and thus eliminate backtracking back over the first character (for example, eliminate the optional part of [-+]?\d+ by making it into [-+\d]\d*) you can use the atomic match operator ?> to eliminate lots of backtracking, as you know that your SQL is well-formed, or rather, it's of little concern to you if the SQL is not well-formed.

Ideally, you have a disjunct set of character classes that start the separate matches. Likely, the disjunct set would be [-+\d] for numbers and ' for strings. If you want to be more careful, you can treat 0[bx]\w+ a bit more discerning, but I wouldn't bother and simply assume instead that the SQL is well-formed.

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