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Re^2: Upgraded SQLite: "database changed" error

by bsb (Priest)
on Jun 05, 2007 at 11:05 UTC ( [id://619342]=note: print w/replies, xml ) Need Help??


in reply to Re: Upgraded SQLite: "database changed" error
in thread Upgraded SQLite: "database changed" error

Thanks for investigating.

There's code within DBD::SQLite's dbdimp.c which does something like the FAQ snippet, but only at the start of an execute, not after calling sqlite's finish within the execute.

The SQL string and bind variables are already retained but the DBD C code so it seems possible to transparently re-prepare. There are even functions to help do this in sqlite (transfer_bindings and reset or something).

Unfortunately, this application needs an ANALYZE after inserting all the basic data in order to run queries with a sane plan. What's more, it's not only the ANALYZE that causes the problems and I also add indexes after bulk loading data. There are probably ways to paper over the problem, something like pinging after each troublesome action.

If it is indeed a problem at the DBD level and can be addressed there then that's my preferred solution. I suspect that there may be a obstacles ahead though.

Update: The new version of prepare doesn't fail on schema changes. This may fully or partially fix the problem.
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Re^3: Upgraded SQLite: "database changed" error
by jbert (Priest) on Jun 05, 2007 at 11:35 UTC
    If your app is in control (and knows when the ANALYZE is going to happen) then perhaps the best approach would be to try and control the use of prepared statement handles?

    If you defer loading your Class::DBI modules until after the bulk load has finished (or are you using Class::DBI for the bulk load?) then it seems that might work around the problem.

    One way to defer the load of some modules until run-time is to wrap the 'use' declaration in a string-eval, e.g. eval "use My::Class::DBI::Module;". Another is to use: 

       require 'My/Class/DBI/Module';
   My::Class::DBI::Module::import();

    [download]
    both of these approaches pull in the module at run-time and so can be used to move the Class::DBI loading until after your ANALYZE, if you perform them in a function rather than at top-level.

    There's probably a better way, though.

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