NAME
Mojo::PgX::Cursor - Cursor Extension for Mojo::Pg
SYNOPSIS
require Mojo::PgX::Cursor;
my $pg = Mojo::PgX::Cursor->new(...);
my $results = $pg->db->cursor('select * from some_table');
while (my $row = $results->hash) {
...
}DESCRIPTION
Mojo::PgX::Cursor is an extension for Mojo::Pg that abstract away the (modest) complications of using a PostgreSQL cursor so that you can use a familiar iterable interface.
PostgreSQL cursors are useful because the DBD::Pg driver has a long-standing limitation that it fetches all results to the client as soon as the statement is executed. This makes, for example, iterating over a whole table very memory-expensive. To work around the issue DBD::Pg recommends using a cursor but with that comes a few complications:
- Cursors must be named.
- Cursors are a resource that should be managed.
- Cursors require a double loop to iterate through all rows.
METHODS
db
Overrides Mojo::Pg's implementation in order to subclass the resulting Mojo::Pg::Database object into a Mojo::PgX::Cursor::Database.
MONKEYPATCH
require Mojo::Pg;
require Mojo::PgX::Cursor;
use Mojo::Util 'monkey_patch';
monkey_patch 'Mojo::Pg::Database', 'cursor', \&Mojo::PgX::Cursor::Database::cursor;Just because you can doesn't mean you should but if you want you can monkey_patch Mojo::Pg::Database rather than swapping out your construction of Mojo::Pg objects with the Mojo::PgX::Cursor subclass.
DISCUSSION
This whole thing would be irrelevant if DBD::Pg did not fetch all rows during execute and since libpq supports that it would be much better to implement that than to implement this. However, I don't really know C and I'm not really sure I want to spend time learning it over another language.
CONTRIBUTING
If you would like to submit bug reports, feature requests, questions, etc. you should create an issue on the <GitHub Issue Tracker|https://github.com/nnutter/mojo-pgx-cursor/issues> for this module.
REFERENCES
LICENSE
Copyright (C) Nathaniel Nutter.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
AUTHOR
Nathaniel Nutter nnutter@cpan.org