txt: ## dist_cpan-CTILMES-DB-MySQL.md
  # 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
  
  ```
  use DB::MySQL;
  my $mysql = DB::MySQL.new();  # You can pass in various options
  
  ```
  
  Execute a query, and get a single value:
  
  ```
  say $mysql.execute('select 42').value;
  # 42
  
  ```
  
  Create a table:
  
  ```
  $mysql.execute('create table foo (x int, y varchar(80))');
  
  ```
  
  Insert some values using placeholders:
  
  ```
  $mysql.query('insert into foo (x,y) values (?,?)', 1, 'this');
  
  ```
  
  Execute a query returning a row as an array or hash;
  
  ```
  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:
  
  ```
  .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:
  
  ```
  .say for $mysql.query('select * from foo').arrays;
  
  ```
  
  ```
  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:
  
  ```
  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:
  
  ```
  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.
  
  ```
  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:
  
  ```
  {
      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.
  
  ```
  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:
  
  ```
  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.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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