NAME

Bio::DB::GFF::Adaptor::dbi::caching_handle -- Cache for database handles

SYNOPSIS

use Bio::DB::GFF::Adaptor::dbi::caching_handle;
$db  = Bio::DB::GFF::Adaptor::dbi::caching_handle->new('dbi:mysql:test');
$sth = $db->prepare('select * from foo');
@h   = $sth->fetch_rowarray;
$sth->finish

DESCRIPTION

This module handles a pool of database handles. It was motivated by the MYSQL driver's {mysql_use_result} attribute, which dramatically improves query speed and memory usage, but forbids additional query statements from being evaluated while an existing one is in use.

This module is a plug-in replacement for vanilla DBI. It automatically activates the {mysql_use_result} attribute for the mysql driver, but avoids problems with multiple active statement handlers by creating new database handles as needed.

USAGE

The object constructor is Bio::DB::GFF::Adaptor::dbi::caching_handle->new(). This is called like DBI->connect() and takes the same arguments. The returned object looks and acts like a conventional database handle.

In addition to all the standard DBI handle methods, this package adds the following:

dbi_quote

Title   : dbi_quote
Usage   : $string = $db->dbi_quote($sql,@args)
Function: perform bind variable substitution
Returns : query string
Args    : the query string and bind arguments
Status  : public

This method replaces the bind variable "?" in a SQL statement with appropriately quoted bind arguments. It is used internally to handle drivers that don't support argument binding.

do_query

Title   : do_query
Usage   : $sth = $db->do_query($query,@args)
Function: perform a DBI query
Returns : a statement handler
Args    : query string and list of bind arguments
Status  : Public

This method performs a DBI prepare() and execute(), returning a statement handle. You will typically call fetch() of fetchrow_array() on the statement handle. The parsed statement handle is cached for later use.

debug

Title   : debug
Usage   : $debug = $db->debug([$debug])
Function: activate debugging messages
Returns : current state of flag
Args    : optional new setting of flag
Status  : public

attribute

Title   : attribute
Usage   : $value = $db->attribute(AttributeName , [$newvalue])
Function: get/set DBI::db handle attribute
Returns : current state of the attribute
Args    : name of the attribute and optional new setting of attribute
Status  : public

 Under Bio::DB::GFF::Adaptor::dbi::caching_handle the DBI::db
 attributes that are usually set using hashref calls are unavailable.
 Use attribute() instead.  For example, instead of:

   $dbh->{AutoCommit} = 0;

 use

   $dbh->attribute(AutoCommit=>0);

BUGS

Report to the author.

SEE ALSO

DBI, Bio::DB::GFF, bioperl

AUTHOR

Lincoln Stein <lstein@cshl.org>.

Copyright (c) 2001 Cold Spring Harbor Laboratory.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.