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Bio::DB::GFF::Adaptor::dbi::caching_handle(3pm) User Contributed Perl Documentation Bio::DB::GFF::Adaptor::dbi::caching_handle(3pm)


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


 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;


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.


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:


 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.


 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.


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


 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;


Report to the author.


DBI, Bio::DB::GFF, bioperl


Lincoln Stein <>.

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.

2020-01-13 perl v5.30.0