roadmap.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "Roadmap 3"
.TH Roadmap 3 "2005-03-25" "perl v5.10.0" "User Contributed Perl Documentation"
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.SH "NAME"
DBI::Roadmap \- Planned Enhancements for the DBI
.PP
Tim Bunce \- 12th November 2004
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
This document gives a high level overview of the future of the Perl
\&\s-1DBI\s0 module.
.PP
The \s-1DBI\s0 module is the standard database interface for Perl applications.
It is used worldwide in countless applications, in every kind of
business, and on platforms from clustered super-computers to PDAs.
Database interface drivers are available for all common databases
and many not-so-common ones.
.PP
The planned enhancements cover testing, performance, high availability
and load balancing, batch statements, Unicode, database portability,
and more.
.PP
Addressing these issues together, in coordinated way, will help
ensure maximum future functionality with minimal disruptive
(incompatible) upgrades.
.SH "SCOPE"
.IX Header "SCOPE"
Broad categories of changes are outlined here along with some
rationale, but implementation details and minor planned enhancements
are omitted.  More details can be found in:
<http://svn.perl.org/modules/dbi/trunk/ToDo>
.SH "CHANGES AND ENHANCEMENTS"
.IX Header "CHANGES AND ENHANCEMENTS"
These are grouped into categories and are not listed in any particular order.
.Sh "Performance"
.IX Subsection "Performance"
The \s-1DBI\s0 has always treated performance as a priority. Some parts
of the implementation, however, remain unoptimized, especially in
relation to threads.
.PP
* When the \s-1DBI\s0 is used with a Perl built with thread support enabled
(such as for Apache mod_perl 2, and some common Linux distributions)
it runs significantly slower. There are two reasons for this and
both can be fixed but require non-trivial changes to both the \s-1DBI\s0
and drivers.
.PP
* Connection pooling in a threaded application, such as mod_perl,
is difficult because \s-1DBI\s0 handles cannot be passed between threads.
An alternative mechanism for passing connections between threads
has been defined, and an experimental connection pool module
implemented using it, but development has stalled.
.PP
* The majority of \s-1DBI\s0 handle creation code is implemented in Perl.
Moving most of this to C will speed up handle creation significantly.
.PP
* The popular \fIfetchrow_hashref()\fR method is many times slower than
\&\fIfetchrow_arrayref()\fR. It has to get the names of the columns, then
create and load a new hash each time. A \f(CW$h\fR\->{FetchHashReuse} attribute
would allow the same hash to be reused each time making \fIfetchrow_hashref()\fR
about the same speed as \fIfetchrow_arrayref()\fR.
.PP
* Support for asynchronous (non-blocking) \s-1DBI\s0 method calls would
enable applications to continue processing in parallel with database
activity.  This is also relevant for \s-1GUI\s0 and other event-driven
applications.  The \s-1DBI\s0 needs to define a standard interface for
this so drivers can implement it in a portable way, where possible.
.PP
These changes would significantly enhance the performance of the
\&\s-1DBI\s0 and many applications which use the \s-1DBI\s0.
.Sh "Testing"
.IX Subsection "Testing"
The \s-1DBI\s0 has a test suite. Every driver has a test suite.  Each is
limited in its scope.  The driver test suite is testing for behavior
that the driver author \fIthinks\fR the \s-1DBI\s0 specifies, but may be
subtly incorrect.  These test suites are poorly maintained because
the return on investment for a single driver is too low to provide
sufficient incentive.
.PP
A common test suite that can be reused by all the drivers is needed.
It would:
.PP
* Improve the quality of the \s-1DBI\s0 and drivers.
.PP
* Ensure all drivers conform to the \s-1DBI\s0 specification.  Easing the
porting of applications between databases, and the implementation
of database independent modules layered over the \s-1DBI\s0.
.PP
* Improve the \s-1DBI\s0 specification by clarifying unclear issues in
order to implement test cases.
.PP
* Encourage expansion of the test suite as driver authors and others
will be motivated by the greater benefits of their contributions.
.PP
* Detect and record optional functionality that a driver has not
yet implemented.
.PP
* Improve the testing of \s-1DBI\s0 subclassing, DBI::PurePerl and the
various \*(L"transparent\*(R" drivers, such as DBD::Proxy and DBD::Multiplex,
by automatically running the test suite through them.
.PP
These changes would improve the quality of all applications using
the \s-1DBI\s0.
.Sh "High Availability and Load Balancing"
.IX Subsection "High Availability and Load Balancing"
* The DBD::Multiplex driver provides a framework to enable a wide
range of dynamic functionality, including support for high-availability,
failover, load-balancing, caching, and access to distributed data.
It is currently being enhanced but development has stalled.
.PP
* The DBD::Proxy module is complex and relatively inefficient because
it's trying to be a complete proxy for most \s-1DBI\s0 method calls.  For
many applications a simpler proxy architecture that operates with
a single round-trip to the server would be simpler, faster, and more