Manpages - DBD_File_HowTo.3pm

package DBD::Foo; use strict; use warnings; use vars qw(@ISA $VERSION); use base qw(DBD::File); use DBI (); $VERSION = “0.001”; package DBD::Foo::dr; use vars qw(@ISA $imp_data_size); @ISA = qw(DBD:::dr); $imp_data_size = 0; package DBD::Foo::db; use vars qw(@ISA $imp_data_size); @ISA = qw(DBD:::db); $imp_data_size = 0; package DBD::Foo::st; use vars qw(@ISA $imp_data_size); @ISA = qw(DBD:::st); $imp_data_size = 0; package DBD::Foo::Statement; use vars qw(@ISA); @ISA = qw(DBD:::Statement); package DBD::Foo::Table; use vars qw(@ISA); @ISA = qw(DBD:::Table); 1;

Tiny, eh? And all you have now is a DBD named foo which will be able to deal with temporary tables, as long as you use SQL::Statement. In DBI::SQL::Nano environments, this DBD can do nothing.

Based on DBI::DBD::SqlEngine::HowTo, we’re now having a driver which could do basic things. Of course, it should now derive from DBD::File instead of DBI::DBD::SqlEngine, shouldn’t it?

DBD::File extends DBI::DBD::SqlEngine to deal with any kind of files. In principle, the only extensions required are to the table class:

package DBD::Foo::Table; sub bootstrap_table_meta { my ( $self, $dbh, $meta, $table ) = @_; # initialize all $meta attributes which might be relevant for # file2table return $self->SUPER::bootstrap_table_meta($dbh, $meta, $table); } sub init_table_meta { my ( $self, $dbh, $meta, $table ) = @_; # called after $meta contains the results from file2table # initialize all missing $meta attributes $self->SUPER::init_table_meta( $dbh, $meta, $table ); }

In case DBD::File::Table::open_file doesn’t open the files as the driver needs that, override it!

sub open_file { my ( $self, $meta, $attrs, $flags ) = @_; # ensure that $meta->{f_dontopen} is set $self->SUPER::open_file( $meta, $attrs, $flags ); # now do what ever needs to be done }

Combined with the methods implemented using the SQL::Statement::Embed guide, the table is full working and you could try a start over.

DBD::File since 0.39 consolidates all persistent meta data of a table into a single structure stored in $dbh->{f_meta}. With DBD::File version 0.41 and DBI::DBD::SqlEngine version 0.05, this consolidation moves to DBI::DBD::SqlEngine. It’s still the $dbh->{$drv_prefix . "_meta"} attribute which cares, so what you learned at this place before, is still valid.

sub init_valid_attributes { my $dbh = $_[0]; $dbh->SUPER::init_valid_attributes (); $dbh->{foo_valid_attrs} = { … }; $dbh->{foo_readonly_attrs} = { … }; $dbh->{foo_meta} = “foo_tables”; return $dbh; }

See updates at User comfort in DBI::DBD::SqlEngine::HowTo.

Now you should have your own DBD::File based driver. Was easy, wasn’t it? But does it work well? Prove it by writing tests and remember to use dbd_edit_mm_attribs from DBI::DBD to ensure testing even rare cases.