Re: [HACKERS] TODO item: Implement Boyer-Moore searching (First time hacker)
От | Tom Lane |
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Тема | Re: [HACKERS] TODO item: Implement Boyer-Moore searching (First time hacker) |
Дата | |
Msg-id | 26522.1220741447@sss.pgh.pa.us обсуждение исходный текст |
Ответ на | Re: [HACKERS] TODO item: Implement Boyer-Moore searching (First time hacker) (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: [HACKERS] TODO item: Implement Boyer-Moore searching (First time hacker)
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Список | pgsql-patches |
I wrote: > I looked this over a bit and was immediately confused by one thing: > the introductory comment says that the skip table size ought to be based > on the length of the haystack, which makes sense to me, but the code is > actually initializing it on the basis of len2, ie, the length of the > needle. Isn't that a bug? Was the same bug present in the tests you > made to determine the best table sizes? BTW, to the extent that you feel like testing a different idea, I would suggest: * don't bother initializing the skiptable when len1 < len2 * otherwise, choose its size based on len1 - len2, not just len1 or len2. This is (one less than) the maximum number of search loop consultations of the skip table that can happen, so it seems like a plausible number, and better than either length alone. regards, tom lane
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