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Re: how to get the ordinal number in list

References (13 earlier) <53e89063$0$29890$c3e8da3$5496439d@news.astraweb.com> <mailman.12844.1407751676.18130.python-list@python.org> <53eab595$0$9505$c3e8da3$5496439d@news.astraweb.com> <mailman.12903.1407893523.18130.python-list@python.org> <roy-BCFAD9.21451512082014@news.panix.com>
Date 2014-08-13 12:06 +1000
Subject Re: how to get the ordinal number in list
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.12906.1407895602.18130.python-list@python.org> (permalink)

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On Wed, Aug 13, 2014 at 11:45 AM, Roy Smith <roy@panix.com> wrote:
> In article <mailman.12903.1407893523.18130.python-list@python.org>,
>  Chris Angelico <rosuav@gmail.com> wrote:
>
>> I like to look at SQL as a language that specifies an end result
>> without specifying how to get there
>
> Well, sure, but sometimes the how to get there is a matter of 10x, or
> 100x, or 1000x in performance.

Of course it can! But generally, the "how to get there" is not
stipulated in the SQL statement. If you say, for instance:

select * from some_table where some_column='some_value';

then an index on some_column will make a huge difference to
performance - without changing this statement at all. In contrast,
taking advantage of an index in BTrieve requires recoding your
program, as the index used is a part of the API call. (At least, this
is true of the particular version of BTrieve that back-ended our
accounting package in the 90s. I was able to turn an overnight job
into a thirty-second job by rewriting it as an external program; the
original is closed-source so I can't be sure, but I suspect most of
that improvement is simply because I used an index.)

SQL itself doesn't even have provision for indexes. The 'CREATE INDEX'
command, found in many databases, is an extension. :)

ChrisA

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Re: how to get the ordinal number in list luofeiyu <elearn2014@gmail.com> - 2014-08-09 10:35 -0700
  Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-09 13:06 +1000
    Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-08 20:48 -0700
      Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-09 11:34 -0400
        Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-10 09:43 +1000
        Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 09:28 -0700
          Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-10 13:10 -0400
            Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 10:34 -0700
              Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-10 14:14 -0400
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 11:26 -0700
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 05:03 +1000
                Re: how to get the ordinal number in list Marko Rauhamaa <marko@pacujo.net> - 2014-08-10 22:14 +0300
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 05:20 +1000
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 22:23 -0700
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 15:46 +1000
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 23:22 -0700
                Re: how to get the ordinal number in list Steven D'Aprano <steve@pearwood.info> - 2014-08-11 08:55 +0000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 19:15 +1000
                Re: how to get the ordinal number in list Marko Rauhamaa <marko@pacujo.net> - 2014-08-11 12:35 +0300
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 19:51 +1000
                Re: how to get the ordinal number in list Marko Rauhamaa <marko@pacujo.net> - 2014-08-11 13:46 +0300
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 21:06 +1000
                Re: how to get the ordinal number in list Steven D'Aprano <steve@pearwood.info> - 2014-08-11 09:44 +0000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 19:53 +1000
                Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-11 21:30 +1000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 20:07 +1000
                Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-13 10:47 +1000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-13 11:31 +1000
                Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-12 21:45 -0400
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-13 12:06 +1000
                Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-11 07:55 -0400
                Re: how to get the ordinal number in list Tim Chase <python.list@tim.thechases.com> - 2014-08-11 07:30 -0500
                Re: how to get the ordinal number in list Marko Rauhamaa <marko@pacujo.net> - 2014-08-11 15:41 +0300
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 22:53 +1000
                Re: how to get the ordinal number in list Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-11 14:57 +0100
                Re: how to get the ordinal number in list Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-10 21:32 +0100
                Re: how to get the ordinal number in list Roy Smith <roy@panix.com> - 2014-08-10 18:01 -0400
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 08:43 +1000
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 20:35 -0700
                Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-11 12:04 +1000
                Re: how to get the ordinal number in list Robert Kern <robert.kern@gmail.com> - 2014-08-11 12:56 +0100
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-11 05:11 -0700
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-11 22:45 +1000
                Re: how to get the ordinal number in list Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-11 15:01 +0100
                Re: how to get the ordinal number in list alister <alister.nospam.ware@ntlworld.com> - 2014-08-11 12:30 +0000
                Re: how to get the ordinal number in list Marko Rauhamaa <marko@pacujo.net> - 2014-08-11 15:41 +0300
                Re: how to get the ordinal number in list Robin Becker <robin@reportlab.com> - 2014-08-11 15:32 +0100
                Re: how to get the ordinal number in list Terry Reedy <tjreedy@udel.edu> - 2014-08-11 18:01 -0400
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-12 09:27 +1000
                Re: how to get the ordinal number in list wxjmfauth@gmail.com - 2014-08-12 00:21 -0700
                Re: how to get the ordinal number in list alister <alister.nospam.ware@ntlworld.com> - 2014-08-12 10:40 +0000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-12 23:39 +1000
                Re: how to get the ordinal number in list alister <alister.nospam.ware@ntlworld.com> - 2014-08-12 18:45 +0000
                Re: how to get the ordinal number in list Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-12 20:16 +0100
                Re: how to get the ordinal number in list "Neil D. Cerutti" <neilc@norwich.edu> - 2014-08-12 13:40 -0400
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-12 11:20 -0700
                Re: how to get the ordinal number in list "Neil D. Cerutti" <neilc@norwich.edu> - 2014-08-12 15:29 -0400
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-12 20:49 -0700
                Re: how to get the ordinal number in list Terry Reedy <tjreedy@udel.edu> - 2014-08-12 18:01 -0400
              Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-11 13:00 +1000
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-10 21:29 -0700
                Re: how to get the ordinal number in list Steven D'Aprano <steve@pearwood.info> - 2014-08-11 10:28 +0000
                Re: how to get the ordinal number in list Rustom Mody <rustompmody@gmail.com> - 2014-08-11 04:49 -0700
                Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-13 12:11 +1000
                Re: how to get the ordinal number in list Chris Angelico <rosuav@gmail.com> - 2014-08-13 12:18 +1000
                Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-13 13:11 +1000
          Re: how to get the ordinal number in list Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-11 03:17 +1000

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