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/lib64/perl5/vendor_perl/DBD/

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File	dir	drwxr-xr-x	2025-06-26 06:14	R D
Gofer	dir	drwxr-xr-x	2025-06-26 06:15	R D
SQLite	dir	drwxr-xr-x	2022-08-08 06:03	R D
DBM.pm	50.874 KB	-rw-r--r--	2013-05-15 09:20	R E G D
ExampleP.pm	11.88 KB	-rw-r--r--	2013-04-04 22:17	R E G D
File.pm	36.438 KB	-rw-r--r--	2013-04-04 22:17	R E G D
Gofer.pm	47.926 KB	-rw-r--r--	2014-06-10 01:06	R E G D
NullP.pm	4.237 KB	-rw-r--r--	2013-04-04 22:17	R E G D
Proxy.pm	28.593 KB	-rw-r--r--	2014-06-10 01:06	R E G D
SQLite.pm	81.932 KB	-rw-r--r--	2013-06-09 15:04	R E G D
Sponge.pm	7.794 KB	-rw-r--r--	2013-04-04 22:17	R E G D
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####################################################################### # # DBD::DBM - a DBI driver for DBM files # # Copyright (c) 2004 by Jeff Zucker < jzucker AT cpan.org > # Copyright (c) 2010-2013 by Jens Rehsack & H.Merijn Brand # # All rights reserved. # # You may freely distribute and/or modify this module under the terms # of either the GNU General Public License (GPL) or the Artistic License, # as specified in the Perl README file. # # USERS - see the pod at the bottom of this file # # DBD AUTHORS - see the comments in the code # ####################################################################### require 5.008; use strict; ################# package DBD::DBM; ################# use base qw( DBD::File ); use vars qw($VERSION $ATTRIBUTION $drh $methods_already_installed); $VERSION = '0.08'; $ATTRIBUTION = 'DBD::DBM by Jens Rehsack'; # no need to have driver() unless you need private methods # sub driver ($;$) { my ( $class, $attr ) = @_; return $drh if ($drh); # do the real work in DBD::File # $attr->{Attribution} = 'DBD::DBM by Jens Rehsack'; $drh = $class->SUPER::driver($attr); # install private methods # # this requires that dbm_ (or foo_) be a registered prefix # but you can write private methods before official registration # by hacking the $dbd_prefix_registry in a private copy of DBI.pm # unless ( $methods_already_installed++ ) { DBD::DBM::st->install_method('dbm_schema'); } return $drh; } sub CLONE { undef $drh; } ##################### package DBD::DBM::dr; ##################### $DBD::DBM::dr::imp_data_size = 0; @DBD::DBM::dr::ISA = qw(DBD::File::dr); # you could put some :dr private methods here # you may need to over-ride some DBD::File::dr methods here # but you can probably get away with just letting it do the work # in most cases ##################### package DBD::DBM::db; ##################### $DBD::DBM::db::imp_data_size = 0; @DBD::DBM::db::ISA = qw(DBD::File::db); use Carp qw/carp/; sub validate_STORE_attr { my ( $dbh, $attrib, $value ) = @_; if ( $attrib eq "dbm_ext" or $attrib eq "dbm_lockfile" ) { ( my $newattrib = $attrib ) =~ s/^dbm_/f_/g; carp "Attribute '$attrib' is depreciated, use '$newattrib' instead" if ($^W); $attrib = $newattrib; } return $dbh->SUPER::validate_STORE_attr( $attrib, $value ); } sub validate_FETCH_attr { my ( $dbh, $attrib ) = @_; if ( $attrib eq "dbm_ext" or $attrib eq "dbm_lockfile" ) { ( my $newattrib = $attrib ) =~ s/^dbm_/f_/g; carp "Attribute '$attrib' is depreciated, use '$newattrib' instead" if ($^W); $attrib = $newattrib; } return $dbh->SUPER::validate_FETCH_attr($attrib); } sub set_versions { my $this = $_[0]; $this->{dbm_version} = $DBD::DBM::VERSION; return $this->SUPER::set_versions(); } sub init_valid_attributes { my $dbh = shift; # define valid private attributes # # attempts to set non-valid attrs in connect() or # with $dbh->{attr} will throw errors # # the attrs here *must* start with dbm_ or foo_ # # see the STORE methods below for how to check these attrs # $dbh->{dbm_valid_attrs} = { dbm_type => 1, # the global DBM type e.g. SDBM_File dbm_mldbm => 1, # the global MLDBM serializer dbm_cols => 1, # the global column names dbm_version => 1, # verbose DBD::DBM version dbm_store_metadata => 1, # column names, etc. dbm_berkeley_flags => 1, # for BerkeleyDB dbm_valid_attrs => 1, # DBD::DBM::db valid attrs dbm_readonly_attrs => 1, # DBD::DBM::db r/o attrs dbm_meta => 1, # DBD::DBM public access for f_meta dbm_tables => 1, # DBD::DBM public access for f_meta }; $dbh->{dbm_readonly_attrs} = { dbm_version => 1, # verbose DBD::DBM version dbm_valid_attrs => 1, # DBD::DBM::db valid attrs dbm_readonly_attrs => 1, # DBD::DBM::db r/o attrs dbm_meta => 1, # DBD::DBM public access for f_meta }; $dbh->{dbm_meta} = "dbm_tables"; return $dbh->SUPER::init_valid_attributes(); } sub init_default_attributes { my ( $dbh, $phase ) = @_; $dbh->SUPER::init_default_attributes($phase); $dbh->{f_lockfile} = '.lck'; return $dbh; } sub get_dbm_versions { my ( $dbh, $table ) = @_; $table ||= ''; my $meta; my $class = $dbh->{ImplementorClass}; $class =~ s/::db$/::Table/; $table and ( undef, $meta ) = $class->get_table_meta( $dbh, $table, 1 ); $meta or ( $meta = {} and $class->bootstrap_table_meta( $dbh, $meta, $table ) ); my $dver; my $dtype = $meta->{dbm_type}; eval { $dver = $meta->{dbm_type}->VERSION(); # *) when we're still alive here, everthing went ok - no need to check for $@ $dtype .= " ($dver)"; }; if ( $meta->{dbm_mldbm} ) { $dtype .= ' + MLDBM'; eval { $dver = MLDBM->VERSION(); $dtype .= " ($dver)"; # (*) }; eval { my $ser_class = "MLDBM::Serializer::" . $meta->{dbm_mldbm}; my $ser_mod = $ser_class; $ser_mod =~ s|::|/|g; $ser_mod .= ".pm"; require $ser_mod; $dver = $ser_class->VERSION(); $dtype .= ' + ' . $ser_class; # (*) $dver and $dtype .= " ($dver)"; # (*) }; } return sprintf( "%s using %s", $dbh->{dbm_version}, $dtype ); } # you may need to over-ride some DBD::File::db methods here # but you can probably get away with just letting it do the work # in most cases ##################### package DBD::DBM::st; ##################### $DBD::DBM::st::imp_data_size = 0; @DBD::DBM::st::ISA = qw(DBD::File::st); sub FETCH { my ( $sth, $attr ) = @_; if ( $attr eq "NULLABLE" ) { my @colnames = $sth->sql_get_colnames(); # XXX only BerkeleyDB fails having NULL values for non-MLDBM databases, # none accept it for key - but it requires more knowledge between # queries and tables storage to return fully correct information $attr eq "NULLABLE" and return [ map { 0 } @colnames ]; } return $sth->SUPER::FETCH($attr); } # FETCH sub dbm_schema { my ( $sth, $tname ) = @_; return $sth->set_err( $DBI::stderr, 'No table name supplied!' ) unless $tname; my $tbl_meta = $sth->{Database}->func( $tname, "f_schema", "get_sql_engine_meta" ) or return $sth->set_err( $sth->{Database}->err(), $sth->{Database}->errstr() ); return $tbl_meta->{$tname}->{f_schema}; } # you could put some :st private methods here # you may need to over-ride some DBD::File::st methods here # but you can probably get away with just letting it do the work # in most cases ############################ package DBD::DBM::Statement; ############################ @DBD::DBM::Statement::ISA = qw(DBD::File::Statement); ######################## package DBD::DBM::Table; ######################## use Carp; use Fcntl; @DBD::DBM::Table::ISA = qw(DBD::File::Table); my $dirfext = $^O eq 'VMS' ? '.sdbm_dir' : '.dir'; my %reset_on_modify = ( dbm_type => "dbm_tietype", dbm_mldbm => "dbm_tietype", ); __PACKAGE__->register_reset_on_modify( \%reset_on_modify ); my %compat_map = ( ( map { $_ => "dbm_$_" } qw(type mldbm store_metadata) ), dbm_ext => 'f_ext', dbm_file => 'f_file', dbm_lockfile => ' f_lockfile', ); __PACKAGE__->register_compat_map( \%compat_map ); sub bootstrap_table_meta { my ( $self, $dbh, $meta, $table ) = @_; $meta->{dbm_type} ||= $dbh->{dbm_type} || 'SDBM_File'; $meta->{dbm_mldbm} ||= $dbh->{dbm_mldbm} if ( $dbh->{dbm_mldbm} ); $meta->{dbm_berkeley_flags} ||= $dbh->{dbm_berkeley_flags}; defined $meta->{f_ext} or $meta->{f_ext} = $dbh->{f_ext}; unless ( defined( $meta->{f_ext} ) ) { my $ext; if ( $meta->{dbm_type} eq 'SDBM_File' or $meta->{dbm_type} eq 'ODBM_File' ) { $ext = '.pag/r'; } elsif ( $meta->{dbm_type} eq 'NDBM_File' ) { # XXX NDBM_File on FreeBSD (and elsewhere?) may actually be Berkeley # behind the scenes and so create a single .db file. if ( $^O =~ /bsd/i or lc($^O) eq 'darwin' ) { $ext = '.db/r'; } elsif ( $^O eq 'SunOS' or $^O eq 'Solaris' or $^O eq 'AIX' ) { $ext = '.pag/r'; # here it's implemented like dbm - just a bit improved } # else wrapped GDBM } defined($ext) and $meta->{f_ext} = $ext; } $self->SUPER::bootstrap_table_meta( $dbh, $meta, $table ); } sub init_table_meta { my ( $self, $dbh, $meta, $table ) = @_; $meta->{f_dontopen} = 1; unless ( defined( $meta->{dbm_tietype} ) ) { my $tie_type = $meta->{dbm_type}; $INC{"$tie_type.pm"} or require "$tie_type.pm"; $tie_type eq 'BerkeleyDB' and $tie_type = 'BerkeleyDB::Hash'; if ( $meta->{dbm_mldbm} ) { $INC{"MLDBM.pm"} or require "MLDBM.pm"; $meta->{dbm_usedb} = $tie_type; $tie_type = 'MLDBM'; } $meta->{dbm_tietype} = $tie_type; } unless ( defined( $meta->{dbm_store_metadata} ) ) { my $store = $dbh->{dbm_store_metadata}; defined($store) or $store = 1; $meta->{dbm_store_metadata} = $store; } unless ( defined( $meta->{col_names} ) ) { defined( $dbh->{dbm_cols} ) and $meta->{col_names} = $dbh->{dbm_cols}; } $self->SUPER::init_table_meta( $dbh, $meta, $table ); } sub open_data { my ( $className, $meta, $attrs, $flags ) = @_; $className->SUPER::open_data( $meta, $attrs, $flags ); unless ( $flags->{dropMode} ) { # TIEING # # XXX allow users to pass in a pre-created tied object # my @tie_args; if ( $meta->{dbm_type} eq 'BerkeleyDB' ) { my $DB_CREATE = BerkeleyDB::DB_CREATE(); my $DB_RDONLY = BerkeleyDB::DB_RDONLY(); my %tie_flags; if ( my $f = $meta->{dbm_berkeley_flags} ) { defined( $f->{DB_CREATE} ) and $DB_CREATE = delete $f->{DB_CREATE}; defined( $f->{DB_RDONLY} ) and $DB_RDONLY = delete $f->{DB_RDONLY}; %tie_flags = %$f; } my $open_mode = $flags->{lockMode} || $flags->{createMode} ? $DB_CREATE : $DB_RDONLY; @tie_args = ( -Filename => $meta->{f_fqbn}, -Flags => $open_mode, %tie_flags ); } else { my $open_mode = O_RDONLY; $flags->{lockMode} and $open_mode = O_RDWR; $flags->{createMode} and $open_mode = O_RDWR | O_CREAT | O_TRUNC; @tie_args = ( $meta->{f_fqbn}, $open_mode, 0666 ); } if ( $meta->{dbm_mldbm} ) { $MLDBM::UseDB = $meta->{dbm_usedb}; $MLDBM::Serializer = $meta->{dbm_mldbm}; } $meta->{hash} = {}; my $tie_class = $meta->{dbm_tietype}; eval { tie %{ $meta->{hash} }, $tie_class, @tie_args }; $@ and croak "Cannot tie(\%h $tie_class @tie_args): $@"; -f $meta->{f_fqfn} or croak( "No such file: '" . $meta->{f_fqfn} . "'" ); } unless ( $flags->{createMode} ) { my ( $meta_data, $schema, $col_names ); if ( $meta->{dbm_store_metadata} ) { $meta_data = $col_names = $meta->{hash}->{"_metadata \0"}; if ( $meta_data and $meta_data =~ m~(.+)~is ) { $schema = $col_names = $1; $schema =~ s~.*(.+).*~$1~is; $col_names =~ s~.*(.+).*~$1~is; } } $col_names ||= $meta->{col_names} || [ 'k', 'v' ]; $col_names = [ split /,/, $col_names ] if ( ref $col_names ne 'ARRAY' ); if ( $meta->{dbm_store_metadata} and not $meta->{hash}->{"_metadata \0"} ) { $schema or $schema = ''; $meta->{hash}->{"_metadata \0"} = "" . "$schema" . "" . join( ",", @{$col_names} ) . "" . ""; } $meta->{schema} = $schema; $meta->{col_names} = $col_names; } } # you must define drop # it is called from execute of a SQL DROP statement # sub drop ($$) { my ( $self, $data ) = @_; my $meta = $self->{meta}; $meta->{hash} and untie %{ $meta->{hash} }; $self->SUPER::drop($data); # XXX extra_files -f $meta->{f_fqbn} . $dirfext and $meta->{f_ext} eq '.pag/r' and unlink( $meta->{f_fqbn} . $dirfext ); return 1; } # you must define fetch_row, it is called on all fetches; # it MUST return undef when no rows are left to fetch; # checking for $ary[0] is specific to hashes so you'll # probably need some other kind of check for nothing-left. # as Janis might say: "undef's just another word for # nothing left to fetch" :-) # sub fetch_row ($$) { my ( $self, $data ) = @_; my $meta = $self->{meta}; # fetch with %each # my @ary = each %{ $meta->{hash} }; $meta->{dbm_store_metadata} and $ary[0] and $ary[0] eq "_metadata \0" and @ary = each %{ $meta->{hash} }; my ( $key, $val ) = @ary; unless ($key) { delete $self->{row}; return; } my @row = ( ref($val) eq 'ARRAY' ) ? ( $key, @$val ) : ( $key, $val ); $self->{row} = @row ? \@row : undef; return wantarray ? @row : \@row; } # you must define push_row except insert_new_row and update_specific_row is defined # it is called on inserts and updates as primitive # sub insert_new_row ($$$) { my ( $self, $data, $row_aryref ) = @_; my $meta = $self->{meta}; my $ncols = scalar( @{ $meta->{col_names} } ); my $nitems = scalar( @{$row_aryref} ); $ncols == $nitems or croak "You tried to insert $nitems, but table is created with $ncols columns"; my $key = shift @$row_aryref; my $exists; eval { $exists = exists( $meta->{hash}->{$key} ); }; $exists and croak "Row with PK '$key' already exists"; $meta->{hash}->{$key} = $meta->{dbm_mldbm} ? $row_aryref : $row_aryref->[0]; return 1; } # this is where you grab the column names from a CREATE statement # if you don't need to do that, it must be defined but can be empty # sub push_names ($$$) { my ( $self, $data, $row_aryref ) = @_; my $meta = $self->{meta}; # some sanity checks ... my $ncols = scalar(@$row_aryref); $ncols < 2 and croak "At least 2 columns are required for DBD::DBM tables ..."; !$meta->{dbm_mldbm} and $ncols > 2 and croak "Without serializing with MLDBM only 2 columns are supported, you give $ncols"; $meta->{col_names} = $row_aryref; return unless $meta->{dbm_store_metadata}; my $stmt = $data->{sql_stmt}; my $col_names = join( ',', @{$row_aryref} ); my $schema = $data->{Database}->{Statement}; $schema =~ s/^[^$]+\((.+)$$/$1/s; $schema = $stmt->schema_str() if ( $stmt->can('schema_str') ); $meta->{hash}->{"_metadata \0"} = "" . "$schema" . "$col_names" . ""; } # fetch_one_row, delete_one_row, update_one_row # are optimized for hash-style lookup without looping; # if you don't need them, omit them, they're optional # but, in that case you may need to define # truncate() and seek(), see below # sub fetch_one_row ($$;$) { my ( $self, $key_only, $key ) = @_; my $meta = $self->{meta}; $key_only and return $meta->{col_names}->[0]; exists $meta->{hash}->{$key} or return; my $val = $meta->{hash}->{$key}; $val = ( ref($val) eq 'ARRAY' ) ? $val : [$val]; my $row = [ $key, @$val ]; return wantarray ? @{$row} : $row; } sub delete_one_row ($$$) { my ( $self, $data, $aryref ) = @_; my $meta = $self->{meta}; delete $meta->{hash}->{ $aryref->[0] }; } sub update_one_row ($$$) { my ( $self, $data, $aryref ) = @_; my $meta = $self->{meta}; my $key = shift @$aryref; defined $key or return; my $row = ( ref($aryref) eq 'ARRAY' ) ? $aryref : [$aryref]; $meta->{hash}->{$key} = $meta->{dbm_mldbm} ? $row : $row->[0]; } sub update_specific_row ($$$$) { my ( $self, $data, $aryref, $origary ) = @_; my $meta = $self->{meta}; my $key = shift @$origary; my $newkey = shift @$aryref; return unless ( defined $key ); $key eq $newkey or delete $meta->{hash}->{$key}; my $row = ( ref($aryref) eq 'ARRAY' ) ? $aryref : [$aryref]; $meta->{hash}->{$newkey} = $meta->{dbm_mldbm} ? $row : $row->[0]; } # you may not need to explicitly DESTROY the ::Table # put cleanup code to run when the execute is done # sub DESTROY ($) { my $self = shift; my $meta = $self->{meta}; $meta->{hash} and untie %{ $meta->{hash} }; $self->SUPER::DESTROY(); } # truncate() and seek() must be defined to satisfy DBI::SQL::Nano # *IF* you define the *_one_row methods above, truncate() and # seek() can be empty or you can use them without actually # truncating or seeking anything but if you don't define the # *_one_row methods, you may need to define these # if you need to do something after a series of # deletes or updates, you can put it in truncate() # which is called at the end of executing # sub truncate ($$) { # my ( $self, $data ) = @_; return 1; } # seek() is only needed if you use IO::File # though it could be used for other non-file operations # that you need to do before "writes" or truncate() # sub seek ($$$$) { # my ( $self, $data, $pos, $whence ) = @_; return 1; } # Th, th, th, that's all folks! See DBD::File and DBD::CSV for other # examples of creating pure perl DBDs. I hope this helped. # Now it's time to go forth and create your own DBD! # Remember to check in with dbi-dev@perl.org before you get too far. # We may be able to make suggestions or point you to other related # projects. 1; __END__ =pod =head1 NAME DBD::DBM - a DBI driver for DBM & MLDBM files =head1 SYNOPSIS use DBI; $dbh = DBI->connect('dbi:DBM:'); # defaults to SDBM_File $dbh = DBI->connect('DBI:DBM(RaiseError=1):'); # defaults to SDBM_File $dbh = DBI->connect('dbi:DBM:dbm_type=DB_File'); # defaults to DB_File $dbh = DBI->connect('dbi:DBM:dbm_mldbm=Storable'); # MLDBM with SDBM_File # or $dbh = DBI->connect('dbi:DBM:', undef, undef); $dbh = DBI->connect('dbi:DBM:', undef, undef, { f_ext => '.db/r', f_dir => '/path/to/dbfiles/', f_lockfile => '.lck', dbm_type => 'BerkeleyDB', dbm_mldbm => 'FreezeThaw', dbm_store_metadata => 1, dbm_berkeley_flags => { '-Cachesize' => 1000, # set a ::Hash flag }, }); and other variations on connect() as shown in the L docs, L and L shown below. Use standard DBI prepare, execute, fetch, placeholders, etc., see L for an example. =head1 DESCRIPTION DBD::DBM is a database management system that works right out of the box. If you have a standard installation of Perl and DBI you can begin creating, accessing, and modifying simple database tables without any further modules. You can add other modules (e.g., SQL::Statement, DB_File etc) for improved functionality. The module uses a DBM file storage layer. DBM file storage is common on many platforms and files can be created with it in many programming languages using different APIs. That means, in addition to creating files with DBI/SQL, you can also use DBI/SQL to access and modify files created by other DBM modules and programs and vice versa. B that in those cases it might be necessary to use a common subset of the provided features. DBM files are stored in binary format optimized for quick retrieval when using a key field. That optimization can be used advantageously to make DBD::DBM SQL operations that use key fields very fast. There are several different "flavors" of DBM which use different storage formats supported by perl modules such as SDBM_File and MLDBM. This module supports all of the flavors that perl supports and, when used with MLDBM, supports tables with any number of columns and insertion of Perl objects into tables. DBD::DBM has been tested with the following DBM types: SDBM_File, NDBM_File, ODBM_File, GDBM_File, DB_File, BerkeleyDB. Each type was tested both with and without MLDBM and with the Data::Dumper, Storable, FreezeThaw, YAML and JSON serializers using the DBI::SQL::Nano or the SQL::Statement engines. =head1 QUICK START DBD::DBM operates like all other DBD drivers - it's basic syntax and operation is specified by DBI. If you're not familiar with DBI, you should start by reading L and the documents it points to and then come back and read this file. If you are familiar with DBI, you already know most of what you need to know to operate this module. Just jump in and create a test script something like the one shown below. You should be aware that there are several options for the SQL engine underlying DBD::DBM, see L. There are also many options for DBM support, see especially the section on L. But here's a sample to get you started. use DBI; my $dbh = DBI->connect('dbi:DBM:'); $dbh->{RaiseError} = 1; for my $sql( split /;\n+/," CREATE TABLE user ( user_name TEXT, phone TEXT ); INSERT INTO user VALUES ('Fred Bloggs','233-7777'); INSERT INTO user VALUES ('Sanjay Patel','777-3333'); INSERT INTO user VALUES ('Junk','xxx-xxxx'); DELETE FROM user WHERE user_name = 'Junk'; UPDATE user SET phone = '999-4444' WHERE user_name = 'Sanjay Patel'; SELECT * FROM user "){ my $sth = $dbh->prepare($sql); $sth->execute; $sth->dump_results if $sth->{NUM_OF_FIELDS}; } $dbh->disconnect; =head1 USAGE This section will explain some usage cases in more detail. To get an overview about the available attributes, see L. =head2 Specifying Files and Directories DBD::DBM will automatically supply an appropriate file extension for the type of DBM you are using. For example, if you use SDBM_File, a table called "fruit" will be stored in two files called "fruit.pag" and "fruit.dir". You should B specify the file extensions in your SQL statements. DBD::DBM recognizes following default extensions for following types: =over 4 =item .pag/r Chosen for dbm_type C<< SDBM_File >>, C<< ODBM_File >> and C<< NDBM_File >> when an implementation is detected which wraps C<< -ldbm >> for C<< NDBM_File >> (e.g. Solaris, AIX, ...). For those types, the C<< .dir >> extension is recognized, too (for being deleted when dropping a table). =item .db/r Chosen for dbm_type C<< NDBM_File >> when an implementation is detected which wraps BerkeleyDB 1.x for C<< NDBM_File >> (typically BSD's, Darwin). =back C<< GDBM_File >>, C<< DB_File >> and C<< BerkeleyDB >> don't usually use a file extension. If your DBM type uses an extension other than one of the recognized types of extensions, you should set the I attribute to the extension B file a bug report as described in DBI with the name of the implementation and extension so we can add it to DBD::DBM. Thanks in advance for that :-). $dbh = DBI->connect('dbi:DBM:f_ext=.db'); # .db extension is used $dbh = DBI->connect('dbi:DBM:f_ext='); # no extension is used # or $dbh->{f_ext}='.db'; # global setting $dbh->{f_meta}->{'qux'}->{f_ext}='.db'; # setting for table 'qux' By default files are assumed to be in the current working directory. To use other directories specify the I attribute in either the connect string or by setting the database handle attribute. For example, this will look for the file /foo/bar/fruit (or /foo/bar/fruit.pag for DBM types that use that extension) my $dbh = DBI->connect('dbi:DBM:f_dir=/foo/bar'); # and this will too: my $dbh = DBI->connect('dbi:DBM:'); $dbh->{f_dir} = '/foo/bar'; # but this is recommended my $dbh = DBI->connect('dbi:DBM:', undef, undef, { f_dir => '/foo/bar' } ); # now you can do my $ary = $dbh->selectall_arrayref(q{ SELECT x FROM fruit }); You can also use delimited identifiers to specify paths directly in SQL statements. This looks in the same place as the two examples above but without setting I: my $dbh = DBI->connect('dbi:DBM:'); my $ary = $dbh->selectall_arrayref(q{ SELECT x FROM "/foo/bar/fruit" }); You can also tell DBD::DBM to use a specified path for a specific table: $dbh->{dbm_tables}->{f}->{file} = q(/foo/bar/fruit); Please be aware that you cannot specify this during connection. If you have SQL::Statement installed, you can use table aliases: my $dbh = DBI->connect('dbi:DBM:'); my $ary = $dbh->selectall_arrayref(q{ SELECT f.x FROM "/foo/bar/fruit" AS f }); See the L for using DROP on tables. =head2 Table locking and flock() Table locking is accomplished using a lockfile which has the same basename as the table's file but with the file extension '.lck' (or a lockfile extension that you supply, see below). This lock file is created with the table during a CREATE and removed during a DROP. Every time the table itself is opened, the lockfile is flocked(). For SELECT, this is a shared lock. For all other operations, it is an exclusive lock (except when you specify something different using the I attribute). Since the locking depends on flock(), it only works on operating systems that support flock(). In cases where flock() is not implemented, DBD::DBM will simply behave as if the flock() had occurred although no actual locking will happen. Read the documentation for flock() for more information. Even on those systems that do support flock(), locking is only advisory - as is always the case with flock(). This means that if another program tries to access the table file while DBD::DBM has the table locked, that other program will *succeed* at opening unless it is also using flock on the '.lck' file. As a result DBD::DBM's locking only really applies to other programs using DBD::DBM or other program written to cooperate with DBD::DBM locking. =head2 Specifying the DBM type Each "flavor" of DBM stores its files in a different format and has different capabilities and limitations. See L for a comparison of DBM types. By default, DBD::DBM uses the C<< SDBM_File >> type of storage since C<< SDBM_File >> comes with Perl itself. If you have other types of DBM storage available, you can use any of them with DBD::DBM. It is strongly recommended to use at least C<< DB_File >>, because C<< SDBM_File >> has quirks and limitations and C<< ODBM_file >>, C<< NDBM_File >> and C<< GDBM_File >> are not always available. You can specify the DBM type using the I attribute which can be set in the connection string or with C<< $dbh->{dbm_type} >> and C<< $dbh->{f_meta}->{$table_name}->{type} >> for per-table settings in cases where a single script is accessing more than one kind of DBM file. In the connection string, just set C<< dbm_type=TYPENAME >> where C<< TYPENAME >> is any DBM type such as GDBM_File, DB_File, etc. Do I use MLDBM as your I as that is set differently, see below. my $dbh=DBI->connect('dbi:DBM:'); # uses the default SDBM_File my $dbh=DBI->connect('dbi:DBM:dbm_type=GDBM_File'); # uses the GDBM_File # You can also use $dbh->{dbm_type} to set the DBM type for the connection: $dbh->{dbm_type} = 'DB_File'; # set the global DBM type print $dbh->{dbm_type}; # display the global DBM type If you have several tables in your script that use different DBM types, you can use the $dbh->{dbm_tables} hash to store different settings for the various tables. You can even use this to perform joins on files that have completely different storage mechanisms. # sets global default of GDBM_File my $dbh->('dbi:DBM:type=GDBM_File'); # overrides the global setting, but only for the tables called # I and I my $dbh->{f_meta}->{foo}->{dbm_type} = 'DB_File'; my $dbh->{f_meta}->{bar}->{dbm_type} = 'BerkeleyDB'; # prints the dbm_type for the table "foo" print $dbh->{f_meta}->{foo}->{dbm_type}; B that you must change the I of a table before you access it for first time. =head2 Adding multi-column support with MLDBM Most of the DBM types only support two columns and even if it would support more, DBD::DBM would only use two. However a CPAN module called MLDBM overcomes this limitation by allowing more than two columns. MLDBM does this by serializing the data - basically it puts a reference to an array into the second column. It can also put almost any kind of Perl object or even B into columns. If you want more than two columns, you B install MLDBM. It's available for many platforms and is easy to install. MLDBM is by default distributed with three serializers - Data::Dumper, Storable, and FreezeThaw. Data::Dumper is the default and Storable is the fastest. MLDBM can also make use of user-defined serialization methods or other serialization modules (e.g. L or L. You select the serializer using the I attribute. Some examples: $dbh=DBI->connect('dbi:DBM:dbm_mldbm=Storable'); # use MLDBM with Storable $dbh=DBI->connect( 'dbi:DBM:dbm_mldbm=MySerializer' # use MLDBM with a user defined module ); $dbh=DBI->connect('dbi::dbm:', undef, undef, { dbm_mldbm => 'YAML' }); # use 3rd party serializer $dbh->{dbm_mldbm} = 'YAML'; # same as above print $dbh->{dbm_mldbm} # show the MLDBM serializer $dbh->{f_meta}->{foo}->{dbm_mldbm}='Data::Dumper'; # set Data::Dumper for table "foo" print $dbh->{f_meta}->{foo}->{mldbm}; # show serializer for table "foo" MLDBM works on top of other DBM modules so you can also set a DBM type along with setting dbm_mldbm. The examples above would default to using SDBM_File with MLDBM. If you wanted GDBM_File instead, here's how: # uses DB_File with MLDBM and Storable $dbh = DBI->connect('dbi:DBM:', undef, undef, { dbm_type => 'DB_File', dbm_mldbm => 'Storable', }); SDBM_File, the default I is quite limited, so if you are going to use MLDBM, you should probably use a different type, see L. See below for some L about MLDBM. =head2 Support for Berkeley DB The Berkeley DB storage type is supported through two different Perl modules - DB_File (which supports only features in old versions of Berkeley DB) and BerkeleyDB (which supports all versions). DBD::DBM supports specifying either "DB_File" or "BerkeleyDB" as a I, with or without MLDBM support. The "BerkeleyDB" dbm_type is experimental and it's interface is likely to change. It currently defaults to BerkeleyDB::Hash and does not currently support ::Btree or ::Recno. With BerkeleyDB, you can specify initialization flags by setting them in your script like this: use BerkeleyDB; my $env = new BerkeleyDB::Env -Home => $dir; # and/or other Env flags $dbh = DBI->connect('dbi:DBM:', undef, undef, { dbm_type => 'BerkeleyDB', dbm_mldbm => 'Storable', dbm_berkeley_flags => { 'DB_CREATE' => DB_CREATE, # pass in constants 'DB_RDONLY' => DB_RDONLY, # pass in constants '-Cachesize' => 1000, # set a ::Hash flag '-Env' => $env, # pass in an environment }, }); Do I set the -Flags or -Filename flags as those are determined and overwritten by the SQL (e.g. -Flags => DB_RDONLY is set automatically when you issue a SELECT statement). Time has not permitted us to provide support in this release of DBD::DBM for further Berkeley DB features such as transactions, concurrency, locking, etc. We will be working on these in the future and would value suggestions, patches, etc. See L and L for further details. =head2 Optimizing the use of key fields Most "flavors" of DBM have only two physical columns (but can contain multiple logical columns as explained above in L). They work similarly to a Perl hash with the first column serving as the key. Like a Perl hash, DBM files permit you to do quick lookups by specifying the key and thus avoid looping through all records (supported by DBI::SQL::Nano only). Also like a Perl hash, the keys must be unique. It is impossible to create two records with the same key. To put this more simply and in SQL terms, the key column functions as the I or UNIQUE INDEX. In DBD::DBM, you can take advantage of the speed of keyed lookups by using DBI::SQL::Nano and a WHERE clause with a single equal comparison on the key field. For example, the following SQL statements are optimized for keyed lookup: CREATE TABLE user ( user_name TEXT, phone TEXT); INSERT INTO user VALUES ('Fred Bloggs','233-7777'); # ... many more inserts SELECT phone FROM user WHERE user_name='Fred Bloggs'; The "user_name" column is the key column since it is the first column. The SELECT statement uses the key column in a single equal comparison - "user_name='Fred Bloggs'" - so the search will find it very quickly without having to loop through all the names which were inserted into the table. In contrast, these searches on the same table are not optimized: 1. SELECT phone FROM user WHERE user_name < 'Fred'; 2. SELECT user_name FROM user WHERE phone = '233-7777'; In #1, the operation uses a less-than (<) comparison rather than an equals comparison, so it will not be optimized for key searching. In #2, the key field "user_name" is not specified in the WHERE clause, and therefore the search will need to loop through all rows to find the requested row(s). B that the underlying DBM storage needs to loop over all I pairs when the optimized fetch is used. SQL::Statement has a massively improved where clause evaluation which costs around 15% of the evaluation in DBI::SQL::Nano - combined with the loop in the DBM storage the speed improvement isn't so impressive. Even if lookups are faster by around 50%, DBI::SQL::Nano and SQL::Statement can benefit from the key field optimizations on updating and deleting rows - and here the improved where clause evaluation of SQL::Statement might beat DBI::SQL::Nano every time the where clause contains not only the key field (or more than one). =head2 Supported SQL syntax DBD::DBM uses a subset of SQL. The robustness of that subset depends on what other modules you have installed. Both options support basic SQL operations including CREATE TABLE, DROP TABLE, INSERT, DELETE, UPDATE, and SELECT. B