Torsten Raudssus > DBIx-Class > DBIx::Class::Storage::DBI

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NAME ^

DBIx::Class::Storage::DBI - DBI storage handler

SYNOPSIS ^

  my $schema = MySchema->connect('dbi:SQLite:my.db');

  $schema->storage->debug(1);

  my @stuff = $schema->storage->dbh_do(
    sub {
      my ($storage, $dbh, @args) = @_;
      $dbh->do("DROP TABLE authors");
    },
    @column_list
  );

  $schema->resultset('Book')->search({
     written_on => $schema->storage->datetime_parser->format_datetime(DateTime->now)
  });

DESCRIPTION ^

This class represents the connection to an RDBMS via DBI. See DBIx::Class::Storage for general information. This pod only documents DBI-specific methods and behaviors.

METHODS ^

connect_info

This method is normally called by "connection" in DBIx::Class::Schema, which encapsulates its argument list in an arrayref before passing them here.

The argument list may contain:

Please note that the DBI docs recommend that you always explicitly set AutoCommit to either 0 or 1. DBIx::Class further recommends that it be set to 1, and that you perform transactions via our "txn_do" in DBIx::Class::Schema method. DBIx::Class will set it to 1 if you do not do explicitly set it to zero. This is the default for most DBDs. See "DBIx::Class and AutoCommit" for details.

DBIx::Class specific connection attributes

In addition to the standard DBI connection attributes, DBIx::Class recognizes the following connection options. These options can be mixed in with your other DBI connection attributes, or placed in a separate hashref (\%extra_attributes) as shown above.

Every time connect_info is invoked, any previous settings for these options will be cleared before setting the new ones, regardless of whether any options are specified in the new connect_info.

on_connect_do

Specifies things to do immediately after connecting or re-connecting to the database. Its value may contain:

a scalar

This contains one SQL statement to execute.

an array reference

This contains SQL statements to execute in order. Each element contains a string or a code reference that returns a string.

a code reference

This contains some code to execute. Unlike code references within an array reference, its return value is ignored.

on_disconnect_do

Takes arguments in the same form as "on_connect_do" and executes them immediately before disconnecting from the database.

Note, this only runs if you explicitly call "disconnect" on the storage object.

on_connect_call

A more generalized form of "on_connect_do" that calls the specified connect_call_METHOD methods in your storage driver.

  on_connect_do => 'select 1'

is equivalent to:

  on_connect_call => [ [ do_sql => 'select 1' ] ]

Its values may contain:

a scalar

Will call the connect_call_METHOD method.

a code reference

Will execute $code->($storage)

an array reference

Each value can be a method name or code reference.

an array of arrays

For each array, the first item is taken to be the connect_call_ method name or code reference, and the rest are parameters to it.

Some predefined storage methods you may use:

do_sql

Executes a SQL string or a code reference that returns a SQL string. This is what "on_connect_do" and "on_disconnect_do" use.

It can take:

a scalar

Will execute the scalar as SQL.

an arrayref

Taken to be arguments to "do" in DBI, the SQL string optionally followed by the attributes hashref and bind values.

a code reference

Will execute $code->($storage) and execute the return array refs as above.

datetime_setup

Execute any statements necessary to initialize the database session to return and accept datetime/timestamp values used with DBIx::Class::InflateColumn::DateTime.

Only necessary for some databases, see your specific storage driver for implementation details.

on_disconnect_call

Takes arguments in the same form as "on_connect_call" and executes them immediately before disconnecting from the database.

Calls the disconnect_call_METHOD methods as opposed to the connect_call_METHOD methods called by "on_connect_call".

Note, this only runs if you explicitly call "disconnect" on the storage object.

disable_sth_caching

If set to a true value, this option will disable the caching of statement handles via "prepare_cached" in DBI.

limit_dialect

Sets a specific SQL::Abstract::Limit-style limit dialect, overriding the default "sql_limit_dialect" setting of the storage (if any). For a list of available limit dialects see DBIx::Class::SQLMaker::LimitDialects.

quote_names

When true automatically sets "quote_char" and "name_sep" to the characters appropriate for your particular RDBMS. This option is preferred over specifying "quote_char" directly.

quote_char

Specifies what characters to use to quote table and column names.

quote_char expects either a single character, in which case is it is placed on either side of the table/column name, or an arrayref of length 2 in which case the table/column name is placed between the elements.

For example under MySQL you should use quote_char => '`', and for SQL Server you should use quote_char => [qw/[ ]/].

name_sep

This parameter is only useful in conjunction with quote_char, and is used to specify the character that separates elements (schemas, tables, columns) from each other. If unspecified it defaults to the most commonly used ..

unsafe

This Storage driver normally installs its own HandleError, sets RaiseError and ShowErrorStatement on, and sets PrintError off on all database handles, including those supplied by a coderef. It does this so that it can have consistent and useful error behavior.

If you set this option to a true value, Storage will not do its usual modifications to the database handle's attributes, and instead relies on the settings in your connect_info DBI options (or the values you set in your connection coderef, in the case that you are connecting via coderef).

Note that your custom settings can cause Storage to malfunction, especially if you set a HandleError handler that suppresses exceptions and/or disable RaiseError.

auto_savepoint

If this option is true, DBIx::Class will use savepoints when nesting transactions, making it possible to recover from failure in the inner transaction without having to abort all outer transactions.

cursor_class

Use this argument to supply a cursor class other than the default DBIx::Class::Storage::DBI::Cursor.

Some real-life examples of arguments to "connect_info" and "connect" in DBIx::Class::Schema

  # Simple SQLite connection
  ->connect_info([ 'dbi:SQLite:./foo.db' ]);

  # Connect via subref
  ->connect_info([ sub { DBI->connect(...) } ]);

  # Connect via subref in hashref
  ->connect_info([{
    dbh_maker => sub { DBI->connect(...) },
    on_connect_do => 'alter session ...',
  }]);

  # A bit more complicated
  ->connect_info(
    [
      'dbi:Pg:dbname=foo',
      'postgres',
      'my_pg_password',
      { AutoCommit => 1 },
      { quote_char => q{"} },
    ]
  );

  # Equivalent to the previous example
  ->connect_info(
    [
      'dbi:Pg:dbname=foo',
      'postgres',
      'my_pg_password',
      { AutoCommit => 1, quote_char => q{"}, name_sep => q{.} },
    ]
  );

  # Same, but with hashref as argument
  # See parse_connect_info for explanation
  ->connect_info(
    [{
      dsn         => 'dbi:Pg:dbname=foo',
      user        => 'postgres',
      password    => 'my_pg_password',
      AutoCommit  => 1,
      quote_char  => q{"},
      name_sep    => q{.},
    }]
  );

  # Subref + DBIx::Class-specific connection options
  ->connect_info(
    [
      sub { DBI->connect(...) },
      {
          quote_char => q{`},
          name_sep => q{@},
          on_connect_do => ['SET search_path TO myschema,otherschema,public'],
          disable_sth_caching => 1,
      },
    ]
  );

on_connect_do

This method is deprecated in favour of setting via "connect_info".

on_disconnect_do

This method is deprecated in favour of setting via "connect_info".

dbh_do

Arguments: ($subref | $method_name), @extra_coderef_args?

Execute the given $subref or $method_name using the new exception-based connection management.

The first two arguments will be the storage object that dbh_do was called on and a database handle to use. Any additional arguments will be passed verbatim to the called subref as arguments 2 and onwards.

Using this (instead of $self->_dbh or $self->dbh) ensures correct exception handling and reconnection (or failover in future subclasses).

Your subref should have no side-effects outside of the database, as there is the potential for your subref to be partially double-executed if the database connection was stale/dysfunctional.

Example:

  my @stuff = $schema->storage->dbh_do(
    sub {
      my ($storage, $dbh, @cols) = @_;
      my $cols = join(q{, }, @cols);
      $dbh->selectrow_array("SELECT $cols FROM foo");
    },
    @column_list
  );

disconnect

Our disconnect method also performs a rollback first if the database is not in AutoCommit mode.

with_deferred_fk_checks

Arguments: $coderef
Return Value: The return value of $coderef

Storage specific method to run the code ref with FK checks deferred or in MySQL's case disabled entirely.

connected

Arguments: none
Return Value: 1|0

Verifies that the current database handle is active and ready to execute an SQL statement (e.g. the connection did not get stale, server is still answering, etc.) This method is used internally by "dbh".

dbh

Returns a $dbh - a data base handle of class DBI. The returned handle is guaranteed to be healthy by implicitly calling "connected", and if necessary performing a reconnection before returning. Keep in mind that this is very expensive on some database engines. Consider using "dbh_do" instead.

select

Arguments: $ident, $select, $condition, $attrs

Handle a SQL select statement.

sql_limit_dialect

This is an accessor for the default SQL limit dialect used by a particular storage driver. Can be overridden by supplying an explicit "limit_dialect" to "connect" in DBIx::Class::Schema. For a list of available limit dialects see DBIx::Class::SQLMaker::LimitDialects.

last_insert_id

Return the row id of the last insert.

_native_data_type

Arguments: $type_name

This API is EXPERIMENTAL, will almost definitely change in the future, and currently only used by ::AutoCast and ::Sybase::ASE.

The default implementation returns undef, implement in your Storage driver if you need this functionality.

Should map types from other databases to the native RDBMS type, for example VARCHAR2 to VARCHAR.

Types with modifiers should map to the underlying data type. For example, INTEGER AUTO_INCREMENT should become INTEGER.

Composite types should map to the container type, for example ENUM(foo,bar,baz) becomes ENUM.

sqlt_type

Returns the database driver name.

bind_attribute_by_data_type

Given a datatype from column info, returns a database specific bind attribute for $dbh->bind_param($val,$attribute) or nothing if we will let the database planner just handle it.

Generally only needed for special case column types, like bytea in postgres.

is_datatype_numeric

Given a datatype from column_info, returns a boolean value indicating if the current RDBMS considers it a numeric value. This controls how "set_column" in DBIx::Class::Row decides whether to mark the column as dirty - when the datatype is deemed numeric a != comparison will be performed instead of the usual eq.

create_ddl_dir

Arguments: $schema \@databases, $version, $directory, $preversion, \%sqlt_args

Creates a SQL file based on the Schema, for each of the specified database engines in \@databases in the given directory. (note: specify SQL::Translator names, not DBI driver names).

Given a previous version number, this will also create a file containing the ALTER TABLE statements to transform the previous schema into the current one. Note that these statements may contain DROP TABLE or DROP COLUMN statements that can potentially destroy data.

The file names are created using the ddl_filename method below, please override this method in your schema if you would like a different file name format. For the ALTER file, the same format is used, replacing $version in the name with "$preversion-$version".

See "METHODS" in SQL::Translator for a list of values for \%sqlt_args. The most common value for this would be { add_drop_table => 1 } to have the SQL produced include a DROP TABLE statement for each table created. For quoting purposes supply quote_table_names and quote_field_names.

If no arguments are passed, then the following default values are assumed:

databases - ['MySQL', 'SQLite', 'PostgreSQL']
version - $schema->schema_version
directory - './'
preversion - <none>

By default, \%sqlt_args will have

 { add_drop_table => 1, ignore_constraint_names => 1, ignore_index_names => 1 }

merged with the hash passed in. To disable any of those features, pass in a hashref like the following

 { ignore_constraint_names => 0, # ... other options }

WARNING: You are strongly advised to check all SQL files created, before applying them.

deployment_statements

Arguments: $schema, $type, $version, $directory, $sqlt_args

Returns the statements used by "deploy" and "deploy" in DBIx::Class::Schema.

The SQL::Translator (not DBI) database driver name can be explicitly provided in $type, otherwise the result of "sqlt_type" is used as default.

$directory is used to return statements from files in a previously created "create_ddl_dir" directory and is optional. The filenames are constructed from "ddl_filename" in DBIx::Class::Schema, the schema name and the $version.

If no $directory is specified then the statements are constructed on the fly using SQL::Translator and $version is ignored.

See "METHODS" in SQL::Translator for a list of values for $sqlt_args.

datetime_parser

Returns the datetime parser class

datetime_parser_type

Defines the datetime parser class - currently defaults to DateTime::Format::MySQL

build_datetime_parser

See "datetime_parser"

is_replicating

A boolean that reports if a particular DBIx::Class::Storage::DBI is set to replicate from a master database. Default is undef, which is the result returned by databases that don't support replication.

lag_behind_master

Returns a number that represents a certain amount of lag behind a master db when a given storage is replicating. The number is database dependent, but starts at zero and increases with the amount of lag. Default in undef

relname_to_table_alias

Arguments: $relname, $join_count

DBIx::Class uses DBIx::Class::Relationship names as table aliases in queries.

This hook is to allow specific DBIx::Class::Storage drivers to change the way these aliases are named.

The default behavior is "$relname_$join_count" if $join_count > 1, otherwise "$relname".

USAGE NOTES ^

DBIx::Class and AutoCommit

DBIx::Class can do some wonderful magic with handling exceptions, disconnections, and transactions when you use AutoCommit => 1 (the default) combined with txn_do for transaction support.

If you set AutoCommit => 0 in your connect info, then you are always in an assumed transaction between commits, and you're telling us you'd like to manage that manually. A lot of the magic protections offered by this module will go away. We can't protect you from exceptions due to database disconnects because we don't know anything about how to restart your transactions. You're on your own for handling all sorts of exceptional cases if you choose the AutoCommit => 0 path, just as you would be with raw DBI.

AUTHORS ^

Matt S. Trout <mst@shadowcatsystems.co.uk>

Andy Grundman <andy@hybridized.org>

LICENSE ^

You may distribute this code under the same terms as Perl itself.

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