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Re: Of Mysql, DBI and PK best practices

by ptum (Priest)
on Apr 17, 2007 at 14:36 UTC ( #610536=note: print w/replies, xml ) Need Help??


in reply to Of Mysql, DBI and PK best practices

Personally, I tend to do two things differently:

  • First, I select a full list of primary keys and put it in a hash. Before I try to do an insert, I check to see if the primary key for that record exists in the hash. If it does, I do an update instead of an insert. If the primary key isn't in the hash, then I do an insert, and add it to the hash if the insert was successful. This seems to be a little cleaner and (potentially) halves my number of SQL executions.
  • Second, I tend to use the RaiseError option in my database connection so that my program doesn't die when DBI encounters an error. I examine $DBI::errstr to specifically identify the nature of the error (in Oracle, you get error codes) so that I cover my bases for the unexpected. There's no sense in attempting an update if the table doesn't exist or your SQL is malformed. I'm not a MySQL guy, but the use of eval and $@ seems less than precise -- you might react to what you think is a duplicate insert error but is really something much more severe.

Update: As noted by kyle above, however, if this code is executed by multiple users/processes, you could end up with a race condition, such that your inserts might still fail because some other guy just added that record since the time that you selected all the primary keys.

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Re^2: Of Mysql, DBI and PK best practices
by dragonchild (Archbishop) on Apr 17, 2007 at 18:28 UTC
    Not unless you do your work within a transaction.

    My criteria for good software:
    1. Does it work?
    2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

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[Corion]: Meh. I get the feeling I should post a call-to-action for people to test their modules with the upcoming 5.26 (or 5.25.latest), as it seems that the smoke testers don't really weed out modules that fail without . in @INC
[Corion]: But without instructions on how to easily test things yourself, I don't think such a call to arms is helpful
[Corion]: (this post on nntp.perl.org / p5p makes it seem to me that smoke testers seem to have a blind spot there)
[Corion]: Hmmm. Maybe setting $ENV{PERL5LIB}=" some path without dot"; perl Makefile.PL; make test already is enough to locally test your module...
[Corion]: Meh, no, will need a BEGIN hook...
[Corion]: ... and PERL5OPT does not like -e in it :-(

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