NAME
Protocol::Database::PostgreSQL - support for the PostgreSQL wire
protocol
SYNOPSIS
use strict;
use warnings;
use mro;
package Example::PostgreSQL::Client;
sub new { bless { @_[1..$#_] }, $_[0] }
sub protocol {
my ($self) = @_;
$self->{protocol} //= Protocol::Database::PostgresQL->new(
outgoing => $self->outgoing,
)
}
# Any received packets will arrive here
sub incoming { shift->{incoming} //= Ryu::Source->new }
# Anything we want to send goes here
sub outgoing { shift->{outgoing} //= Ryu::Source->new }
...
# We raise events on our incoming source in this example -
# if you prefer to handle each message as it's extracted you
# could add that directly in the loop
$self->incoming
->switch_str(
sub { $_->type },
authentication_request => sub { ... },
sub { warn 'unknown message - ' . $_->type }
);
# When there's something to write, we'll get an event here
$self->outgoing
->each(sub { $sock->write($_) });
while(1) {
$sock->read(my $buf, 1_000_000);
while(my $msg = $self->protocol->extract_message(\$buf)) {
$self->incoming->emit($msg);
}
}
DESCRIPTION
Provides protocol-level support for PostgreSQL 7.4+, as defined in
http://www.postgresql.org/docs/current/static/protocol.html.
How do I use this?
The short answer: don't.
Use Database::Async::Engine::PostgreSQL instead, unless you're writing
a driver for talking to PostgreSQL (or compatible) systems.
This distribution provides the abstract protocol handling, meaning that
it understands the packets that make up the PostgreSQL communication
protocol, but it does not attempt to send or receive those packets
itself. You need to provide the transport layer (typically this would
involve TCP or Unix sockets).
Connection states
Possible states:
* Unconnected - we have a valid instantiated PostgreSQL object, but
no connection yet.
* Connected - transport layer has made a connection for us
* AuthRequested - the server has challenged us to identify
* Authenticated - we have successfully identified with the server
* Idle - session is active and ready for commands
* Parsing - a statement has been passed to the server for parsing
* Describing - the indicated statement is being described, called
after the transport layer has sent the Describe request
* Binding - parameters for a given query have been transmitted
* Executing - we have sent a request to execute
* ShuttingDown - terminate request sent
* CopyIn - the server is expecting data for a COPY command
Message types
The "type" in Protocol::Database::Backend for incoming messages can
currently include the following:
* send_request - Called each time there is a new message to be sent
to the other side of the connection.
* authenticated - Called when authentication is complete
* copy_data - we have received data from an ongoing COPY request
* copy_complete - the active COPY request has completed
For the client, the following additional callbacks are available:
* request_ready - the server is ready for the next request
* bind_complete - a Bind request has completed
* close_complete - the Close request has completed
* command_complete - the requested command has finished, this will
typically be followed by an on_request_ready event
* copy_in_response - indicates that the server is ready to receive
COPY data
* copy_out_response - indicates that the server is ready to send COPY
data
* copy_both_response - indicates that the server is ready to exchange
COPY data (for replication)
* data_row - data from the current query
* empty_query - special-case response when sent an empty query, can
be used for 'ping'. Typically followed by on_request_ready
* error - server has raised an error
* function_call_result - results from a function call
* no_data - indicate that a query returned no data, typically
followed by on_request_ready
* notice - server has sent us a notice
* notification - server has sent us a NOTIFY
* parameter_description - parameters are being described
* parameter_status - parameter status...
* parse_complete - parsing is done
* portal_suspended - the portal has been suspended, probably hit the
row limit
* ready_for_query - we're ready for queries
* row_description - descriptive information about the rows we're
likely to be seeing shortly
And there are also these potential events back from the server:
* copy_fail - the frontend is indicating that the copy has failed
* describe - request for something to be described
* execute - request execution of a given portal
* flush - request flush
* function_call - request execution of a given function
* parse - request to parse something
* password - password information
* query - simple query request
* ssl_request - we have an SSL request
* startup_message - we have an SSL request
* sync - sync request
* terminate - termination request
METHODS
new
Instantiate a new object. Blesses an empty hashref and calls
"configure", subclasses can bypass this entirely and just call
"configure" directly after instantiation.
configure
Does the real preparation for the object.
frontend_bind
Bind parameters to an existing prepared statement.
frontend_copy_data
frontend_close
frontend_copy_done
frontend_describe
Describe expected SQL results
frontend_execute
Execute either a named or anonymous portal (prepared statement with
bind vars)
frontend_parse
Parse SQL for a prepared statement
frontend_password_message
Password data, possibly encrypted depending on what the server
specified.
frontend_query
Simple query
frontend_startup_message
Initial mesage informing the server which database and user we want
frontend_sync
Synchonise after a prepared statement has finished execution.
frontend_terminate
is_authenticated
Returns true if we are authenticated (and can start sending real data).
is_first_message
Returns true if this is the first message, as per
http://developer.postgresql.org/pgdocs/postgres/protocol-overview.html:
"For historical reasons, the very first message sent by the client (the startup message)
has no initial message-type byte."
send_message
Send a message.
method_for_frontend_type
Returns the method name for the given frontend type.
is_known_frontend_message_type
Returns true if the given frontend type is one that we know how to
handle.
message
Creates a new message of the given type.
handle_message
Handle an incoming message from the server.
message_length
Returns the length of the given message.
simple_query
Send a simple query to the server - only supports plain queries (no
bind parameters).
copy_data
Send copy data to the server.
copy_done
Indicate that the COPY data from the client is complete.
backend_state
Accessor for current backend state.
is_ready
Returns true if we're ready to send more data to the server.
send_copy_data
Send COPY data to the server. Takes an arrayref and replaces any
reserved characters with quoted versions.
build_message
Construct a new message.
SEE ALSO
Some PostgreSQL-related modules - plenty of things build on these so
have a look at the relevant reverse deps if you're after something
higher level:
* DBD::Pg - uses the official library and (unlike this module)
provides full support for DBI
* Pg::PQ - another libpq wrapper
* Postgres - quite an old (1998) libpq binding
* Pg - slightly less old (2000) libpq binding
* DBD::PgPP - provides another pure-Perl implemmentation, with the
focus on DBI compatibility
Other related database protocols:
* Protocol::MySQL - Oracle's popular database product
* Protocol::TDS - the tabular data stream protocol, mainly of
interest for SQL Server users
AUTHOR
Tom Molesworth <
[email protected]>
LICENSE
Copyright Tom Molesworth 2010-2019. Licensed under the same terms as
Perl itself.
