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.
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@vpservices.com> with a cc to
<dbi-dev@perl.org>.
The usage is the same as for standard DBI with the exception
that you need to set the enviornment 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 DBIif 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} = 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?)
Trace functionality is more limited and the code to handle tracing is
only embeded 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.
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).
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.
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.
