NAME
Protocol::PostgreSQL::Statement - prepared statement handling
VERSION
version 0.008
SYNOPSIS
use Protocol::PostgreSQL;
my %cache;
# Helper method to apply the returned values
my $set_cache = sub {
my ($sth, $row) = @_;
my ($k, $v) = map { $row->[$_]{data} } 0..1;
warn "Set $k to $v\n";
$cache{$k} = $v;
};
# Prepared statement to insert a new value, called when no existing value was found
my $add_sth = Protocol::PostgreSQL::Statement->new(
dbh => $dbh,
sql => 'insert into sometable (name) values $1 returning id, name',
on_data_row => $set_cache,
on_no_data => sub {
die "Had no response when trying to add value";
}
);
# Find existing value from table
my $find_sth = Protocol::PostgreSQL::Statement->new(
dbh => $dbh,
sql => 'select id, name from sometable where id = ?',
on_data_row => $set_cache,
on_no_data => sub {
my ($sth) = shift;
warn "No data found, inserting\n";
$add_sth->execute($sth->current_bind_values);
}
);
$find_sth->execute(471, "some data");
print "Value for 471 was " . $cache{471};DESCRIPTION
Provides prepared-statement support for Protocol::PostgreSQL.
Sequence of events for a prepared statement:
Parse - check the supplied SQL, generate a prepared statement
Bind - binds values to a statement to generate a portal ('' is the empty portal)
Execute - execute a given portal
Sync - inform the server we're done and that we want to go back to "ReadyForQuery" in Protocol::PostgreSQL state.
Once an execute is running, we avoid sending anything else to the server until we get a ReadyForQuery response.
On instantiation, the statement will be parsed immediately. When this is complete, we are able to bind then execute. Any requests to bind or execute before the statement is ready will be queued.
METHODS
new
Instantiate a new object, takes the following named parameters:
dbh - Protocol::PostgreSQL-compatible object for the parent database handle
sql - actual SQL query to run, with placeholders specified as ?
statement - name to assign to this statement
Will send the parse request immediately.
parse_complete
Callback when parsing is complete.
execute
Bind variables to the current statement.
current_bind_values
Returns the bind values from the currently-executing query, suitable for passing to "execute".
data_row
Callback when we have a data row.
Maintains a running count of how many rows we've seen, and passes the data on to the data_row callback if defined.
command_complete
Callback for end of statement. We'll hit this if we completed without error and there's no more data available to read.
Will call the no_data callback if we had no rows, and the command_complete callback in either case.
bind_complete
Called when the bind is complete. Since our bind+execute handling is currently combined, this doesn't do anything at the moment.
_execute
Execute this query.
describe
Describe this query. Causes PostgreSQL to send RowDescription response indicating what we expect to get back from the server. Beats trying to parse the query for ourselves although it incurs an extra send/receive for each statement.
row_description
Accessor to return or update the internal row description information.
on_ready
Called when we've finished parsing and describing this query.
finish
Finish the current statement.
Should issue a Sync to trigger a ReadyForQuery response, but that's now handled elsewhere.
dbh
Accessor for the database handle (Protocol::PostgreSQL object).
sap
Generate a callback with weakened copy of $self.
AUTHOR
Tom Molesworth <cpan@entitymodel.com>
LICENSE
Copyright Tom Molesworth 2010-2011. Licensed under the same terms as Perl itself.