Re: How to use index in WHERE int = float
От | Andrus |
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Тема | Re: How to use index in WHERE int = float |
Дата | |
Msg-id | 8AF3AFF2E5824671853122F2A1C7752B@andrusnotebook обсуждение исходный текст |
Ответ на | Re: How to use index in WHERE int = float (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-general |
> It would be far simpler to fix your query generator to not emit the > useless "0 or". I'm using ODBC and npgsql drivers. Those drivers replace parameters automatically. E.q. for npgsql or every other ADO .NET I can write "SELECT * FROM (:param1 OR (x IN SELECT y FROM z) AND :param2) ... etc. param1, param2, ..., paramn etc. are entered by user and passed to driver as parameters. Proposed solution requires: 1. Stop using this type parameter replacement. Write case statements for every possible paramn combination in application code, total n! case statements. or 2. Create expression parser which understands syntax for every backend version and simplifies expression as string before passing to backend. > Even if we made the planner deal with that, the number of cycles it > would expend to recover from the generator's stupidity would be several > orders of magnitude higher than the number of cycles needed to not be so > stupid. Proposed solution requires re-writing ODBC and npgsql and possibly every other driver to add expression parser and constant optimization to it in client side. This seems to be huge work and no one dbms does not implement this. In this case every query is processed two times. I do'nt understand how this takes less time that processing query once in backend. Andrus.
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