Hello, this patch allow to use Knuth-Morrison-Pratt algorithm for strpos() function (see Cormen et al. Introduction to Algorithms, MIT Press, 2001).
It also works with multibyte wchar. In worst case current brute force strpos() takes O(n * m) (n && m is length of strings) time (example: 'aaa...aaab' search in 'aaa...aaa'). KMP algo always takes O(n + m) time. To check this someone need to create a table with one text attribute, and insert several thousands record 'aa..aa'(for example, with lenght = 1000) . After execute "select count(*) from test where strpos(a, 'aaa....aab') > 0;" on current and modified version. Also, I advise to use "select .. where strpos(att, 'word') > 0;" instead "select .. where attr like '%word%'" (strpos must be faster than regex). In general, this belongs to artificial expressions. In natural language KMP is equal (execution time) current strpos() nearly. ---- Ajtkulov Pavel [EMAIL PROTECTED] P. S. Sorry for prime English.
varlena.c.patch
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