DB::MySQL - MySQL access for Perl 6 =================================== [![Build Status](https://travis-ci.org/CurtTilmes/perl6-dbmysql.svg)](https://travis-ci.org/CurtTilmes/perl6-dbmysql) This is a reimplementation of Perl 6 bindings for MySQL. Basic usage ----------- ```perl6 use DB::MySQL; my $mysql = DB::MySQL.new(); # You can pass in various options ``` Execute a query, and get a single value: ```perl6 say $mysql.execute('select 42').value; # 42 ``` Create a table: ```perl6 $mysql.execute('create table foo (x int, y varchar(80))'); ``` Insert some values using placeholders: ```perl6 $mysql.query('insert into foo (x,y) values (?,?)', 1, 'this'); ``` Execute a query returning a row as an array or hash; ```perl6 say $mysql.query('select * from foo where x = ?', 1).array; say $mysql.query('select * from foo where x = ?', 1).hash; ``` Execute a query returning a bunch of rows as arrays or hashes: ```perl6 .say for $mysql.query('select * from foo').arrays; .say for $mysql.query('select * from foo').hashes; ``` `.query()` caches a prepared statement, and can have placeholders and arguments - `.execute()` does not prepare/cache and can't have placeholders. Both can return results. Installation ------------ This module relies on `libmysqlclient.so`. For Ubuntu, I install this with: ``` sudo apt install libmysqlclient-dev ``` I worked with version 5.7 of the API. It may or may not work with other versions. You can see the client version with: ``` perl6 -MDB::MySQL::Native -e 'say mysql_get_client_info' ``` There are likely 64-bit Linux dependencies in the code. Patches welcome if someone wants to make it on other OSes. Connection Information ---------------------- There are many options that can be specified to `DB::MySQL.new()`: * `:host` - defaults to `localhost` * `:port` - defaults to `3306` * `:user` * `:password` * `:socket` * `:database` - optional, sets current database * `:connect-timeout` - timeout in seconds for a connect attempt. * `:read-timeout` - timeout in seconds for each attempt to read from the servers. * `:write-timeout` - timeout in seconds for each attempt to write to the server. * `:default-file` - Read options from the named file instead of `my.cnf`. * `:group` - defaults to 'client'. Reads options from the specified group in the `.my.cnf` file. Undefine this to ignore defaults file. The easiest way to connect is to put your options in `.my.cnf`. DB::MySQL::Connection ---------------------- The main **DB::MySQL** object acts as a factory for connections, maintaining a cache of connections already created. A new connection can be requested with the `.db` method, but often this isn't needed. When you are finished with a connection, you can explicitly return it to the cache with `.finish`. You can call `.query()` or `.execute()` on the main **DB::SQLite** object, but all they really do is allocate a **DB::SQLite::Connection** (either from the cache, or create a new one) and call those methods on it, then return the connection to the cache. These are equivalent: ```perl6 .say for $mysql.query('select * from foo').arrays; ``` ```perl6 my $db = $mysql.db; .say for $mysql.query('select * from foo').arrays; $db.finish; ``` The connection object also has some extra methods for separately preparing and executing the query: ```perl6 my $db = $mysql.db; my $sth = $db.prepare('insert into foo (x,y) values (?,?)'); $sth.execute(1, 'this'); $sth.execute(2, 'that'); $db.finish; ``` You can also call `.finish()` on the statement: ```perl6 my $sth = $mysql.db.prepare('insert into foo (x,y) values (?,?)'); $sth.execute(1, 'this'); $sth.execute(2, 'that'); $sth.finish; ``` The statement will finish the associated connection, returning it to the cache. Yet another way to do it is to pass `:finish` in to the execute. ```perl6 my $sth = $mysql.db.prepare('insert into foo (x,y) values (?,?)'); $sth.execute(1, 'this'); $sth.execute(2, 'that', :finish); ``` And finally, a cool Perl 6ish way is the `will` trait to install a Phaser directly on the variable: ```perl6 { my $sth will leave { .finish } = $mysql.db.prepare('insert into foo (x,y) values (?,?)'); $sth.execute(1, 'this'); $sth.execute(2, 'that'); } ``` Calling `.prepare()` on the **DB::MySQL::Connection** prepares and returns a **DB::MySQL::Statement** that can then be `.execute()`ed. The prepared statement is also retained in a cache with the connection. If the same statement is prepared again on the same connection, the cached object will be returned instead of re-preparing. If you don't want it to be cached, you can pass in the `:nocache` option. ```perl6 my $sth = $mysql.db.prepare('insert into foo (x,y) values (?,?)', :nocache); $sth.execute(1, 'this'); $sth.execute(2, 'that', :finish); ``` You must still take care to call `.finish()` to return the connection to the connection cache so it will get reused. (Or take care NOT to call `.finish()` if you don't want the connection to be reused, possibly in another thread.) For the main object, or the connection object, `.execute()` is used instead of `.query()` if you don't need placeholders/arguments. Transactions ------------ The database connection object can also manage transactions with the `.begin`, `.commit`, and `.rollback` methods: ```perl6 my $db = $mysql.db; my $sth = $db.prepare('insert into foo (x,y) values (?,?)'); $db.begin; $sth.execute(1, 'this'); $sth.execute(2, 'that'); $db.commit; $db.finish; ``` The `begin`/`commit` ensure that the statements between them happen atomically, either all or none. Transactions can also dramatically improve performance for some actions, such as performing thousands of inserts/deletes/updates since the indexes for the affected table can be updated in bulk once for the entire transaction. If you `.finish` the database prior to a `.commit`, an uncommitted transaction will automatically be rolled back. As a convenience, `.commit` also returns the database object, so you can just `$db.commit.finish`. Results ------- Calling `.query()` on a **DB::MySQL** or **DB::MySQL::Connection**, or calling `.execute()` on a **DB::SQLite::Statement** with an SQL SELECT or something that returns data, a `DB::SQLite::Result` object will be returned. The query results can be consumed from that object with the following methods: * `.value` - a single scalar result * `.array` - a single array of results from one row * `.hash` - a single hash of results from one row * `.arrays` - a sequence of arrays of results from all rows * `.hashes` - a sequence of hashes of results from all rows If the query isn't a select or otherwise doesn't return data, such as an INSERT, UPDATE, or DELETE, it will return the number of rows affected. By default, the entire result of the query is retrieved immediately from the server to the client. You can pass in the `:nostore` option to `.query` or `.execute` to avoid this behavior. It will then retrieve the results from the server as you consume them on the client. This will hold up server resources while you retrieve the results, so exercise care with this. Exceptions ---------- All database errors, including broken SQL queries, are thrown as exceptions. Acknowledgements ---------------- Inspiration taken from the existing Perl6 [DBIish](https://github.com/perl6/DBIish) module as well as the Perl 5 [Mojo::Pg](http://mojolicious.org/perldoc/Mojo/Pg) from the Mojolicious project. License ------- Portions thanks to DBIish: Copyright © 2009-2016, the DBIish contributors All rights reserved. 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