Access to the database itself from your Perl function can be done
via the function spi_exec_query
described
below, or via an experimental module
DBD::PgSPI
(also available at CPAN mirror sites). This module makes available a
DBI-compliant database-handle named
$pg_dbh
that can be used to perform queries with
normal DBI
syntax.
PL/Perl itself presently provides two additional Perl commands:
spi_exec_query
(query
[, max-rows
])
spi_exec_query
(command
)
Executes an SQL command. Here is an example of a query
(SELECT
command) with the optional maximum
number of rows:
$rv = spi_exec_query('SELECT * FROM my_table', 5);
This returns up to 5 rows from the table
my_table
. If my_table
has a column my_column
, you can get that
value from row $i
of the result like this:
$foo = $rv->{rows}[$i]->{my_column};
The total number of rows returned from a SELECT
query can be accessed like this:
$nrows = $rv->{processed}
Here is an example using a different command type:
$query = "INSERT INTO my_table VALUES (1, 'test')"; $rv = spi_exec_query($query);
You can then access the command status (e.g.,
SPI_OK_INSERT
) like this:
$res = $rv->{status};
To get the number of rows affected, do:
$nrows = $rv->{processed};
Here is a complete example:
CREATE TABLE test ( i int, v varchar ); INSERT INTO test (i, v) VALUES (1, 'first line'); INSERT INTO test (i, v) VALUES (2, 'second line'); INSERT INTO test (i, v) VALUES (3, 'third line'); INSERT INTO test (i, v) VALUES (4, 'immortal'); CREATE FUNCTION test_munge() RETURNS SETOF test AS $$ my $res = []; my $rv = spi_exec_query('select i, v from test;'); my $status = $rv->{status}; my $nrows = $rv->{processed}; foreach my $rn (0 .. $nrows - 1) { my $row = $rv->{rows}[$rn]; $row->{i} += 200 if defined($row->{i}); $row->{v} =~ tr/A-Za-z/a-zA-Z/ if (defined($row->{v})); push @$res, $row; } return $res; $$ LANGUAGE plperl; SELECT * FROM test_munge();
elog
(level
, msg
)
Emit a log or error message. Possible levels are
DEBUG
, LOG
, INFO
,
NOTICE
, WARNING
, and ERROR
.
ERROR
raises an error condition; if this is not trapped by the surrounding
Perl code, the error propagates out to the calling query, causing
the current transaction or subtransaction to be aborted. This
is effectively the same as the Perl die
command.
The other levels only generate messages of different
priority levels.
Whether messages of a particular priority are reported to the client,
written to the server log, or both is controlled by the
log_min_messages and
client_min_messages configuration
variables. See Section 16.4, “Run-time Configuration” for more
information.