DBI::PurePerl(3) User Contributed Perl Documentation DBI::PurePerl(3)
NAME
DBI::PurePerl -- a DBI emulation using pure perl (no C/XS compilation
required)
SYNOPSIS
BEGIN { $ENV{DBI_PUREPERL} = 2 }
use DBI;
DESCRIPTION
This is a pure perl emulation of the DBI internals. In almost all
cases you will be better off using standard DBI since the portions of
the standard version written in C make it *much* faster.
However, if you are in a situation where it isn't possible to install a
compiled version of standard DBI, and you're using pure-perl DBD
drivers, then this module allows you to use most common features of DBI
without needing any changes in your scripts.
EXPERIMENTAL STATUS
DBI::PurePerl is new so please treat it as experimental pending more
extensive testing. So far it has passed all tests with DBD::CSV,
DBD::AnyData, DBD::XBase, DBD::Sprite, DBD::mysqlPP. Please send bug
reports to Jeff Zucker at <jeff AT vpservices.com> with a cc to
<dbi-dev AT perl.org>.
USAGE
The usage is the same as for standard DBI with the exception that you
need to set the environment variable DBI_PUREPERL if you want to use
the PurePerl version.
DBI_PUREPERL == 0 (the default) Always use compiled DBI, die
if it isn't properly compiled & installed
DBI_PUREPERL == 1 Use compiled DBI if it is properly compiled
& installed, otherwise use PurePerl
DBI_PUREPERL == 2 Always use PurePerl
You may set the enviornment variable in your shell (e.g. with set or
setenv or export, etc) or else set it in your script like this:
BEGIN { $ENV{DBI_PUREPERL}=2 }
before you "use DBI;".
INSTALLATION
In most situations simply install DBI (see the DBI pod for details).
In the situation in which you can not install DBI itself, you may
manually copy DBI.pm and PurePerl.pm into the appropriate directories.
For example:
cp DBI.pm /usr/jdoe/mylibs/.
cp PurePerl.pm /usr/jdoe/mylibs/DBI/.
Then add this to the top of scripts:
BEGIN {
$ENV{DBI_PUREPERL} = 1; # or =2
unshift @INC, '/usr/jdoe/mylibs';
}
(Or should we perhaps patch Makefile.PL so that if DBI_PUREPERL is set
to 2 prior to make, the normal compile process is skipped and the files
are installed automatically?)
DIFFERENCES BETWEEN DBI AND DBI::PurePerl
Attributes
Boolean attributes still return boolean values but the actual values
used may be different, i.e., 0 or undef instead of an empty string.
Some handle attributes are either not supported or have very limited
functionality:
ActiveKids
InactiveDestroy
AutoInactiveDestroy
Kids
Taint
TaintIn
TaintOut
(and probably others)
Tracing
Trace functionality is more limited and the code to handle tracing is
only embedded into DBI:PurePerl if the DBI_TRACE environment variable
is defined. To enable total tracing you can set the DBI_TRACE
environment variable as usual. But to enable individual handle tracing
using the trace() method you also need to set the DBI_TRACE environment
variable, but set it to 0.
Parameter Usage Checking
The DBI does some basic parameter count checking on method calls.
DBI::PurePerl doesn't.
Speed
DBI::PurePerl is slower. Although, with some drivers in some contexts
this may not be very significant for you.
By way of example... the test.pl script in the DBI source distribution
has a simple benchmark that just does:
my $null_dbh = DBI->connect('dbi:NullP:','','');
my $i = 10_000;
$null_dbh->prepare('') while $i--;
In other words just prepares a statement, creating and destroying a
statement handle, over and over again. Using the real DBI this runs at
~4550 handles per second whereas DBI::PurePerl manages ~2800 per second
on the same machine (not too bad really).
May not fully support hash()
If you want to use type 1 hash, i.e., "hash($string,1)" with
DBI::PurePerl, you'll need version 1.56 or higher of Math::BigInt
(available on CPAN).
Doesn't support preparse()
The DBI->preparse() method isn't supported in DBI::PurePerl.
Doesn't support DBD::Proxy
There's a subtle problem somewhere I've not been able to identify.
DBI::ProxyServer seem to work fine with DBI::PurePerl but DBD::Proxy
does not work 100% (which is sad because that would be far more useful
:) Try re-enabling t/80proxy.t for DBI::PurePerl to see if the problem
that remains will affect you're usage.
Others
can() - doesn't have any special behaviour
Please let us know if you find any other differences between DBI and
DBI::PurePerl.
AUTHORS
Tim Bunce and Jeff Zucker.
Tim provided the direction and basis for the code. The original idea
for the module and most of the brute force porting from C to Perl was
by Jeff. Tim then reworked some core parts to boost the performance and
accuracy of the emulation. Thanks also to Randal Schwartz and John
Tobey for patches.
COPYRIGHT
Copyright (c) 2002 Tim Bunce Ireland.
See COPYRIGHT section in DBI.pm for usage and distribution rights.
perl v5.16.3 2013-04-04 DBI::PurePerl(3)