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Manual Reference Pages  -  DBIX::CLASS::STORAGE::DBI (3)

.ds Aq ’

NAME

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

CONTENTS

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:
o The same 4-element argument set one would normally pass to connect in DBI, optionally followed by extra attributes recognized by DBIx::Class:



  $connect_info_args = [ $dsn, $user, $password, \%dbi_attributes?, \%extra_attributes? ];



o A single code reference which returns a connected DBI database handle optionally followed by extra attributes recognized by DBIx::Class:



  $connect_info_args = [ sub { DBI->connect (...) }, \%extra_attributes? ];



o A single hashref with all the attributes and the dsn/user/password mixed together:



  $connect_info_args = [{
    dsn => $dsn,
    user => $user,
    password => $pass,
    %dbi_attributes,
    %extra_attributes,
  }];

  $connect_info_args = [{
    dbh_maker => sub { DBI->connect (...) },
    %dbi_attributes,
    %extra_attributes,
  }];



This is particularly useful for Catalyst based applications, allowing the following config (Config::General style):



  <Model::DB>
    schema_class   App::DB
    <connect_info>
      dsn          dbi:mysql:database=test
      user         testuser
      password     TestPass
      AutoCommit   1
    </connect_info>
  </Model::DB>



The dsn/user/password combination can be substituted by the dbh_maker key whose value is a coderef that returns a connected DBI database handle

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 <B>expensiveB> on some database engines. Consider using dbh_do instead.

    connect_call_datetime_setup

A no-op stub method, provided so that one can always safely supply the connection option



 on_connect_call => datetime_setup



This way one does not need to know in advance whether the underlying storage requires any sort of hand-holding when dealing with calendar data.

    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 <B>EXPERIMENTALB>, 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.

This method is always called after the driver has been determined and a DBI connection has been established. Therefore you can refer to DBI::$constant and/or DBD::$driver::$constant directly, without worrying about loading the correct modules.

    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_identifiers.

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 in DBIx::Class::Storage 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
Return Value: $alias
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.

FURTHER QUESTIONS?

Check the list of additional DBIC resources.

COPYRIGHT AND LICENSE

This module is free software copyright by the DBIx::Class (DBIC) authors. You can redistribute it and/or modify it under the same terms as the DBIx::Class library.
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