NAME¶
Rose::DB - A DBI wrapper and abstraction layer.
SYNOPSIS¶
package My::DB;
use Rose::DB;
our @ISA = qw(Rose::DB);
My::DB->register_db(
domain => 'development',
type => 'main',
driver => 'Pg',
database => 'dev_db',
host => 'localhost',
username => 'devuser',
password => 'mysecret',
server_time_zone => 'UTC',
);
My::DB->register_db(
domain => 'production',
type => 'main',
driver => 'Pg',
database => 'big_db',
host => 'dbserver.acme.com',
username => 'dbadmin',
password => 'prodsecret',
server_time_zone => 'UTC',
);
My::DB->default_domain('development');
My::DB->default_type('main');
...
$db = My::DB->new;
my $dbh = $db->dbh or die $db->error;
$db->begin_work or die $db->error;
$dbh->do(...) or die $db->error;
$db->commit or die $db->error;
$db->do_transaction(sub
{
$dbh->do(...);
$sth = $dbh->prepare(...);
$sth->execute(...);
while($sth->fetch) { ... }
$dbh->do(...);
})
or die $db->error;
$dt = $db->parse_timestamp('2001-03-05 12:34:56.123');
$val = $db->format_timestamp($dt);
$dt = $db->parse_datetime('2001-03-05 12:34:56');
$val = $db->format_datetime($dt);
$dt = $db->parse_date('2001-03-05');
$val = $db->format_date($dt);
$bit = $db->parse_bitfield('0x0AF', 32);
$val = $db->format_bitfield($bit);
...
DESCRIPTION¶
Rose::DB is a wrapper and abstraction layer for DBI-related functionality. A
Rose::DB object "has a" DBI object; it is not a subclass of DBI.
Please see the tutorial (perldoc Rose::DB::Tutorial) for an example usage
scenario that reflects "best practices" for this module.
Tip: Are you looking for an object-relational mapper (ORM)? If so, please
see the Rose::DB::Object module. Rose::DB::Object is an ORM that uses this
module to manage its database connections. Rose::DB alone is simply a data
source abstraction layer; it is not an ORM.
DATABASE SUPPORT¶
Rose::DB currently supports the following DBI database drivers:
DBD::Pg (PostgreSQL)
DBD::mysql (MySQL)
DBD::SQLite (SQLite)
DBD::Informix (Informix)
DBD::Oracle (Oracle)
Rose::DB will attempt to service an unsupported database using a generic
implementation that may or may not work. Support for more drivers may be added
in the future. Patches are welcome.
All database-specific behavior is contained and documented in the subclasses of
Rose::DB. Rose::DB's constructor method (
new()) returns a
database-specific subclass of Rose::DB, chosen based on the driver value of
the selected data source. The default mapping of databases to Rose::DB
subclasses is:
DBD::Pg -> Rose::DB::Pg
DBD::mysql -> Rose::DB::MySQL
DBD::SQLite -> Rose::DB::SQLite
DBD::Informix -> Rose::DB::Informix
DBD::Oracle -> Rose::DB::Oracle
This mapping can be changed using the driver_class class method.
The Rose::DB object method documentation found here defines the purpose of each
method, as well as the default behavior of the method if it is not overridden
by a subclass. You must read the subclass documentation to learn about
behaviors that are specific to each type of database.
Subclasses may also add methods that do not exist in the parent class, of
course. This is yet another reason to read the documentation for the subclass
that corresponds to your data source's database software.
FEATURES¶
The basic features of Rose::DB are as follows.
Data Source Abstraction¶
Instead of dealing with "databases" that exist on "hosts" or
are located via some vendor-specific addressing scheme, Rose::DB deals with
"logical" data sources. Each logical data source is currently backed
by a single "physical" database (basically a single DBI connection).
Multiplexing, fail-over, and other more complex relationships between logical
data sources and physical databases are not part of Rose::DB. Some basic types
of fail-over may be added to Rose::DB in the future, but right now the mapping
is strictly one-to-one. (I'm also currently inclined to encourage multiplexing
functionality to exist in a layer above Rose::DB, rather than within it or in
a subclass of it.)
The driver type of the data source determines the functionality of all methods
that do vendor-specific things (e.g., column value parsing and formatting).
Rose::DB identifies data sources using a two-level namespace made of a
"domain" and a "type". Both are arbitrary strings. If left
unspecified, the default domain and default type (accessible via Rose::DB's
default_domain and default_type class methods) are assumed.
There are many ways to use the two-level namespace, but the most common is to
use the domain to represent the current environment (e.g.,
"development", "staging", "production") and then
use the type to identify the logical data source within that environment
(e.g., "report", "main", "archive")
A typical deployment scenario will set the default domain using the
default_domain class method as part of the configure/install process. Within
application code, Rose::DB objects can be constructed by specifying type
alone:
$main_db = Rose::DB->new(type => 'main');
$archive_db = Rose::DB->new(type => 'archive');
If there is only one database type, then all Rose::DB objects can be
instantiated with a bare constructor call like this:
$db = Rose::DB->new;
Again, remember that this is just one of many possible uses of domain and type.
Arbitrarily complex scenarios can be created by nesting namespaces within one
or both parameters (much like how Perl uses "::" to create a
multi-level namespace from single strings).
The important point is the abstraction of data sources so they can be identified
and referred to using a vocabulary that is entirely independent of the actual
DSN (data source names) used by DBI behind the scenes.
Database Handle Life-Cycle Management¶
When a Rose::DB object is destroyed while it contains an active DBI database
handle, the handle is explicitly disconnected before destruction. Rose::DB
supports a simple retain/release reference-counting system which allows a
database handle to out-live its parent Rose::DB object.
In the simplest case, Rose::DB could be used for its data source abstractions
features alone. For example, transiently creating a Rose::DB and then
retaining its DBI database handle before it is destroyed:
$main_dbh = Rose::DB->new(type => 'main')->retain_dbh
or die Rose::DB->error;
$aux_dbh = Rose::DB->new(type => 'aux')->retain_dbh
or die Rose::DB->error;
If the database handle was simply extracted via the dbh method instead of
retained with retain_dbh, it would be disconnected by the time the statement
completed.
# WRONG: $dbh will be disconnected immediately after the assignment!
$dbh = Rose::DB->new(type => 'main')->dbh or die Rose::DB->error;
Certain semantically identical column types are handled differently in different
databases. Date and time columns are good examples. Although many databases
store month, day, year, hours, minutes, and seconds using a
"datetime" column type, there will likely be significant differences
in how each of those databases expects to receive such values, and how they're
returned.
Rose::DB is responsible for converting the wide range of vendor-specific column
values for a particular column type into a single form that is convenient for
use within Perl code. Rose::DB also handles the opposite task, taking input
from the Perl side and converting it into the appropriate format for a
specific database. Not all column types that exist in the supported databases
are handled by Rose::DB, but support will expand in the future.
Many column types are specific to a single database and do not exist elsewhere.
When it is reasonable to do so, vendor-specific column types may be
"emulated" by Rose::DB for the benefit of other databases. For
example, an ARRAY value may be stored as a specially formatted string in a
VARCHAR field in a database that does not have a native ARRAY column type.
Rose::DB does
NOT attempt to present a unified column type system,
however. If a column type does not exist in a particular kind of database,
there should be no expectation that Rose::DB will be able to parse and format
that value type on behalf of that database.
High-Level Transaction Support¶
Transactions may be started, committed, and rolled back in a variety of ways
using the DBI database handle directly. Rose::DB provides wrappers to do the
same things, but with different error handling and return values. There's also
a method (do_transaction) that will execute arbitrary code within a single
transaction, automatically handling rollback on failure and commit on success.
SUBCLASSING¶
Subclassing is
strongly encouraged and generally works as expected. (See
the tutorial for a complete example.) There is, however, the question of how
class data is shared with subclasses. Here's how it works for the various
pieces of class data.
- alias_db, modify_db, register_db,
unregister_db, unregister_domain
- By default, all subclasses share the same data source "registry"
with Rose::DB. To provide a private registry for your subclass (the
recommended approach), see the example in the documentation for the
registry method below.
- default_domain, default_type
- If called with no arguments, and if the attribute was never set for this
class, then a left-most, breadth-first search of the parent classes is
initiated. The value returned is taken from first parent class encountered
that has ever had this attribute set.
(These attributes use the inheritable_scalar method type as defined in
Rose::Class::MakeMethods::Generic.)
- driver_class, default_connect_options
- These hashes of attributes are inherited by subclasses using a one-time,
shallow copy from a superclass. Any subclass that accesses or manipulates
the hash in any way will immediately get its own private copy of the hash
as it exists in the superclass at the time of the access or
manipulation.
The superclass from which the hash is copied is the closest ("least
super") class that has ever accessed or manipulated this hash. The
copy is a "shallow" copy, duplicating only the keys and values.
Reference values are not recursively copied.
Setting to hash to undef (using the 'reset' interface) will cause it to be
re-copied from a superclass the next time it is accessed.
(These attributes use the inheritable_hash method type as defined in
Rose::Class::MakeMethods::Generic.)
SERIALIZATION¶
A Rose::DB object may contain a DBI database handle, and DBI database handles
usually don't survive the serialize process intact. Rose::DB objects also hide
database passwords inside closures, which also don't serialize well. In order
for a Rose::DB object to survive serialization, custom hooks are required.
Rose::DB has hooks for the Storable serialization module, but there is an
important caveat. Since Rose::DB objects are blessed into a dynamically
generated class (derived from the driver class), you must load your
Rose::DB-derived class with all its registered data sources before you can
successfully thaw a frozen Rose::DB-derived object. Here's an example.
Imagine that this is your Rose::DB-derived class:
package My::DB;
use Rose::DB;
our @ISA = qw(Rose::DB);
My::DB->register_db(
domain => 'dev',
type => 'main',
driver => 'Pg',
...
);
My::DB->register_db(
domain => 'prod',
type => 'main',
driver => 'Pg',
...
);
My::DB->default_domain('dev');
My::DB->default_type('main');
In one program, a "My::DB" object is frozen using Storable:
# my_freeze_script.pl
use My::DB;
use Storable qw(nstore);
# Create My::DB object
$db = My::DB->new(domain => 'dev', type => 'main');
# Do work...
$db->dbh->db('CREATE TABLE some_table (...)');
...
# Serialize $db and store it in frozen_data_file
nstore($db, 'frozen_data_file');
Now another program wants to thaw out that "My::DB" object and use it.
To do so, it must be sure to load the My::DB module (which registers all its
data sources when loaded)
before attempting to deserialize the
"My::DB" object serialized by "my_freeze_script.pl".
# my_thaw_script.pl
# IMPORTANT: load db modules with all data sources registered before
# attempting to deserialize objects of this class.
use My::DB;
use Storable qw(retrieve);
# Retrieve frozen My::DB object from frozen_data_file
$db = retrieve('frozen_data_file');
# Do work...
$db->dbh->db('DROP TABLE some_table');
...
Note that this rule about loading a Rose::DB-derived class with all its data
sources registered prior to deserializing such an object only applies if the
serialization was done in a different process. If you freeze and thaw within
the same process, you don't have to worry about it.
ENVIRONMENT¶
There are two ways to alter the initial Rose::DB data source registry.
- •
- The ROSEDB_DEVINIT file or module, which can add, modify, or remove data
sources and alter the default domain and type.
- •
- The ROSEDBRC file, which can modify existing data sources.
ROSEDB_DEVINIT¶
The "ROSEDB_DEVINIT" file or module is used during development,
usually to set up data sources for a particular developer's database or
project. If the "ROSEDB_DEVINIT" environment variable is set, it
should be the name of a Perl module or file. If it is a Perl module and that
module has a "fixup()" subroutine, it will be called as a class
method after the module is loaded.
If the "ROSEDB_DEVINIT" environment variable is not set, or if the
specified file does not exist or has errors, then it defaults to the package
name "Rose::DB::Devel::Init::username", where "username"
is the account name of the current user.
Note: if the
getpwuid() function is unavailable (as is often the
case on Windows versions of perl) then this default does not apply and the
loading of the module named "Rose::DB::Devel::Init::username" is not
attempted.
The "ROSEDB_DEVINIT" file or module may contain arbitrary Perl code
which will be loaded and evaluated in the context of Rose::DB. Example:
Rose::DB->default_domain('development');
Rose::DB->modify_db(domain => 'development',
type => 'main_db',
database => 'main',
username => 'jdoe',
password => 'mysecret');
1;
Remember to end the file with a true value.
The "ROSEDB_DEVINIT" file or module must be read explicitly by calling
the auto_load_fixups class method.
ROSEDBRC¶
The "ROSEDBRC" file contains configuration "fix-up"
information. This file is most often used to dynamically set passwords that
are too sensitive to be included directly in the source code of a
Rose::DB-derived class.
The path to the fix-up file is determined by the "ROSEDBRC"
environment variable. If this variable is not set, or if the file it points to
does not exist, then it defaults to "/etc/rosedbrc".
This file should be in YAML format. To read this file, you must have either
YAML::Syck or some reasonably modern version of YAML installed (0.66 or later
recommended). YAML::Syck will be preferred if both are installed.
The "ROSEDBRC" file's contents have the following structure:
---
somedomain:
sometype:
somemethod: somevalue
---
otherdomain:
othertype:
othermethod: othervalue
Each entry modifies an existing registered data source. Any valid registry entry
object method can be used (in place of "somemethod" and
"othermethod" in the YAML example above).
This file must be read explicitly by calling the auto_load_fixups class method
after setting up all your data sources. Example:
package My::DB;
use Rose::DB;
our @ISA = qw(Rose::DB);
__PACKAGE__->use_private_registry;
# Register all data sources
__PACKAGE__->register_db(
domain => 'development',
type => 'main',
driver => 'Pg',
database => 'dev_db',
host => 'localhost',
username => 'devuser',
password => 'mysecret',
);
...
# Load fix-up files, if any
__PACKAGE__->auto_load_fixups;
CLASS METHODS¶
- alias_db PARAMS
- Make one data source an alias for another by pointing them both to the
same registry entry. PARAMS are name/value pairs that must include domain
and type values for both the source and alias parameters. Example:
Rose::DB->alias_db(source => { domain => 'dev', type => 'main' },
alias => { domain => 'dev', type => 'aux' });
This makes the "dev/aux" data source point to the same registry
entry as the "dev/main" data source. Modifications to either
registry entry (via modify_db) will be reflected in both.
- auto_load_fixups
- Attempt to load both the YAML-based ROSEDBRC and Perl-based ROSEDB_DEVINIT
fix-up files, if any exist, in that order. The ROSEDBRC file will modify
the data source registry of the calling class. See the ENVIRONMENT section
above for more information.
- db_cache [CACHE]
- Get or set the Rose::DB::Cache-derived object used to cache Rose::DB
objects on behalf of this class. If no such object exists, a new cache
object of db_cache_class class will be created, stored, and returned.
- db_cache_class [CLASS]
- Get or set the name of the Rose::DB::Cache-derived class used to cache
Rose::DB objects on behalf of this class. The default value is
Rose::DB::Cache.
- db_exists PARAMS
- Returns true of the data source specified by PARAMS is registered, false
otherwise. PARAMS are name/value pairs for "domain" and
"type". If they are omitted, they default to default_domain and
default_type, respectively. If default values do not exist, a fatal error
will occur. If a single value is passed instead of name/value pairs, it is
taken as the value of the "type" parameter.
- default_connect_options [HASHREF | PAIRS]
- Get or set the default DBI connect options hash. If a reference to a hash
is passed, it replaces the default connect options hash. If a series of
name/value pairs are passed, they are added to the default connect options
hash.
The default set of default connect options is:
AutoCommit => 1,
RaiseError => 1,
PrintError => 1,
ChopBlanks => 1,
Warn => 0,
See the connect_options object method for more information on how the
default connect options are used.
- default_domain [DOMAIN]
- Get or set the default data source domain. See the "Data Source
Abstraction" section for more information on data source
domains.
- default_type [TYPE]
- Get or set the default data source type. See the "Data Source
Abstraction" section for more information on data source types.
- driver_class DRIVER [, CLASS]
- Get or set the subclass used for DRIVER. The DRIVER argument is
automatically converted to lowercase. (Driver names are effectively
case-insensitive.)
$class = Rose::DB->driver_class('Pg'); # get
Rose::DB->driver_class('pg' => 'MyDB::Pg'); # set
The default mapping of driver names to class names is as follows:
mysql -> Rose::DB::MySQL
pg -> Rose::DB::Pg
informix -> Rose::DB::Informix
sqlite -> Rose::DB::SQLite
oracle -> Rose::DB::Oracle
generic -> Rose::DB::Generic
The class mapped to the special driver name "generic" will be used
for any driver name that does not have an entry in the map.
See the documentation for the new method for more information on how the
driver influences the class of objects returned by the constructor.
- default_keyword_function_calls [BOOL]
- Get or set a boolean default value for the keyword_function_calls object
attribute. Defaults to the value of the
"ROSE_DB_KEYWORD_FUNCTION_CALLS" environment variable, it set to
a defined value, or false otherwise.
- modify_db PARAMS
- Modify a data source, setting the attributes specified in PARAMS, where
PARAMS are name/value pairs. Any Rose::DB object method that sets a data
source configuration value is a valid parameter name.
# Set new username for data source identified by domain and type
Rose::DB->modify_db(domain => 'test',
type => 'main',
username => 'tester');
PARAMS should include values for both the "type" and
"domain" parameters since these two attributes are used to
identify the data source. If they are omitted, they default to
default_domain and default_type, respectively. If default values do not
exist, a fatal error will occur. If there is no data source defined for
the specified "type" and "domain", a fatal error will
occur.
- prepare_cache_for_apache_fork
- This is a convenience method that is equivalent to the following call:
Rose::DB->db_cache->prepare_for_apache_fork()
Any arguments passed to this method are passed on to the call to the
db_cache's prepare_for_apache_fork method.
Please read the Rose::DB::Cache documentation, particularly the
documentation for the use_cache_during_apache_startup method for more
information.
- register_db PARAMS
- Registers a new data source with the attributes specified in PARAMS, where
PARAMS are name/value pairs. Any Rose::DB object method that sets a data
source configuration value is a valid parameter name.
PARAMS must include a value for the "driver" parameter. If
the "type" or "domain" parameters are omitted or
undefined, they default to the return values of the default_type and
default_domain class methods, respectively.
The "type" and "domain" are used to identify the data
source. If either one is missing, a fatal error will occur. See the
"Data Source Abstraction" section for more information on data
source types and domains.
The "driver" is used to determine which class objects will be
blessed into by the Rose::DB constructor, new. The driver name is
automatically converted to lowercase. If it is missing, a fatal error will
occur.
In most deployment scenarios, register_db is called early in the compilation
process to ensure that the registered data sources are available when the
"real" code runs.
Database registration can be included directly in your Rose::DB subclass.
This is the recommended approach. Example:
package My::DB;
use Rose::DB;
our @ISA = qw(Rose::DB);
# Use a private registry for this class
__PACKAGE__->use_private_registry;
# Register data sources
My::DB->register_db(
domain => 'development',
type => 'main',
driver => 'Pg',
database => 'dev_db',
host => 'localhost',
username => 'devuser',
password => 'mysecret',
);
My::DB->register_db(
domain => 'production',
type => 'main',
driver => 'Pg',
database => 'big_db',
host => 'dbserver.acme.com',
username => 'dbadmin',
password => 'prodsecret',
);
...
Another possible approach is to consolidate data source registration in a
single module which is then "use"ed early on in the code path.
For example, imagine a mod_perl web server environment:
# File: MyCorp/DataSources.pm
package MyCorp::DataSources;
My::DB->register_db(
domain => 'development',
type => 'main',
driver => 'Pg',
database => 'dev_db',
host => 'localhost',
username => 'devuser',
password => 'mysecret',
);
My::DB->register_db(
domain => 'production',
type => 'main',
driver => 'Pg',
database => 'big_db',
host => 'dbserver.acme.com',
username => 'dbadmin',
password => 'prodsecret',
);
...
# File: /usr/local/apache/conf/startup.pl
use My::DB; # your Rose::DB subclass
use MyCorp::DataSources; # register all data sources
...
Data source registration can happen at any time, of course, but it is most
useful when all application code can simply assume that all the data
sources are already registered. Doing the registration as early as
possible (e.g., directly in your Rose::DB subclass, or in a
"startup.pl" file that is loaded from an apache/mod_perl web
server's "httpd.conf" file) is the best way to create such an
environment.
Note that the data source registry serves as an initial source of
information for Rose::DB objects. Once an object is instantiated, it is
independent of the registry. Changes to an object are not reflected in the
registry, and changes to the registry are not reflected in existing
objects.
- registry [REGISTRY]
- Get or set the Rose::DB::Registry-derived object that manages and stores
the data source registry. It defaults to an "empty"
Rose::DB::Registry object. Remember that setting a new registry will
replace the existing registry and all the data sources registered in it.
Note that Rose::DB subclasses will inherit the base class's
Rose::DB::Registry object and will therefore inherit all existing registry
entries and share the same registry namespace as the base class. This may
or may not be what you want.
In most cases, it's wise to give your subclass its own private registry if
it inherits directly from Rose::DB. To do that, just set a new registry
object in your subclass. Example:
package My::DB;
use Rose::DB;
our @ISA = qw(Rose::DB);
# Create a private registry for this class:
#
# either explicitly:
# use Rose::DB::Registry;
# __PACKAGE__->registry(Rose::DB::Registry->new);
#
# or use the convenience method:
__PACKAGE__->use_private_registry;
...
Further subclasses of "My::DB" may then inherit its registry
object, if desired, or may create their own private registries in the
manner shown above.
- unregister_db PARAMS
- Unregisters the data source having the "type" and
"domain" specified in PARAMS, where PARAMS are name/value pairs.
Returns true if the data source was unregistered successfully, false if it
did not exist in the first place. Example:
Rose::DB->unregister_db(type => 'main', domain => 'test');
PARAMS must include values for both the "type" and
"domain" parameters since these two attributes are used to
identify the data source. If either one is missing, a fatal error will
occur.
Unregistering a data source removes all knowledge of it. This may be harmful
to any existing Rose::DB objects that are associated with that data
source.
- unregister_domain DOMAIN
- Unregisters an entire domain. Returns true if the domain was unregistered
successfully, false if it did not exist in the first place. Example:
Rose::DB->unregister_domain('test');
Unregistering a domain removes all knowledge of all of the data sources that
existed under it. This may be harmful to any existing Rose::DB objects
that are associated with any of those data sources.
- use_cache_during_apache_startup [BOOL]
- This is a convenience method that is equivalent to the following call:
Rose::DB->db_cache->use_cache_during_apache_startup(...)
The boolean argument passed to this method is passed on to the call to the
db_cache's use_cache_during_apache_startup method.
Please read the Rose::DB::Cache's use_cache_during_apache_startup
documentation for more information.
- use_private_registry
- This method is used to give a class its own private registry. In other
words, this:
__PACKAGE__->use_private_registry;
is roughly equivalent to this:
use Rose::DB::Registry;
__PACKAGE__->registry(Rose::DB::Registry->new);
CONSTRUCTORS¶
- new PARAMS
- Constructs a new object based on PARAMS, where PARAMS are name/value
pairs. Any object method is a valid parameter name. Example:
$db = Rose::DB->new(type => 'main', domain => 'qa');
If a single argument is passed to new, it is used as the "type"
value:
$db = Rose::DB->new(type => 'aux');
$db = Rose::DB->new('aux'); # same thing
Each Rose::DB object is associated with a particular data source, defined by
the type and domain values. If these are not part of PARAMS, then the
default values are used. If you do not want to use the default values for
the type and domain attributes, you should specify them in the constructor
PARAMS.
The default type and domain can be set using the default_type and
default_domain class methods. See the "Data Source Abstraction"
section for more information on data sources.
Object attributes are set based on the registry entry specified by the
"type" and "domain" parameters. This registry entry
must exist or a fatal error will occur (with one exception; see below).
Any additional PARAMS will override the values taken from the registry
entry.
If "type" and "domain" parameters are not passed, but a
"driver" parameter is passed, then a new "empty"
object will be returned. Examples:
# This is ok, even if no registered data sources exist
$db = Rose::DB->new(driver => 'sqlite');
The object returned by new will be derived from a database-specific driver
class, chosen based on the driver value of the selected data source. If
there is no registered data source for the specified type and domain, a
fatal error will occur.
The default driver-to-class mapping is as follows:
pg -> Rose::DB::Pg
mysql -> Rose::DB::MySQL
informix -> Rose::DB::Informix
oracle -> Rose::DB::Oracle
sqlite -> Rose::DB::SQLite
You can change this mapping with the driver_class class method.
- new_or_cached PARAMS
- Constructs or returns a Rose::DB object based on PARAMS, where PARAMS are
any name/value pairs that can be passed to the new method. If the
db_cache's get_db method returns an existing Rose::DB object that matches
PARAMS, then it is returned. Otherwise, a new Rose::DB object is created,
stored in the db_cache, then returned.
See the Rose::DB::Cache documentation to learn about the cache API and the
default implementation.
OBJECT METHODS¶
- begin_work
- Attempt to start a transaction by calling the begin_work method on the DBI
database handle.
If necessary, the database handle will be constructed and connected to the
current data source. If this fails, undef is returned. If there is no
registered data source for the current "type" and
"domain", a fatal error will occur.
If the "AutoCommit" database handle attribute is false, the handle
is assumed to already be in a transaction and
Rose::DB::Constants::IN_TRANSACTION (-1) is returned. If the call to DBI's
begin_work method succeeds, 1 is returned. If it fails, undef is
returned.
- commit
- Attempt to commit the current transaction by calling the commit method on
the DBI database handle. If the DBI database handle does not exist or is
not connected, 0 is returned.
If the "AutoCommit" database handle attribute is true, the handle
is assumed to not be in a transaction and
Rose::DB::Constants::IN_TRANSACTION (-1) is returned. If the call to DBI's
commit method succeeds, 1 is returned. If it fails, undef is
returned.
- connect
- Constructs and connects the DBI database handle for the current data
source, calling dbi_connect to create a new DBI database handle if none
exists. If there is no registered data source for the current type and
domain, a fatal error will occur.
If any post_connect_sql statement failed to execute, the database handle is
disconnected and then discarded.
If the database handle returned by dbi_connect was originally connected by
another Rose::DB-derived object (e.g., if a subclass's custom
implementation of dbi_connect calls DBI's connect_cached method) then the
post_connect_sql statements will not be run, nor will any custom DBI
attributes be applied (e.g., Rose::DB::MySQL's mysql_enable_utf8
attribute).
Returns true if the database handle was connected successfully and all
post_connect_sql statements (if any) were run successfully, false
otherwise.
- connect_option NAME [, VALUE]
- Get or set a single connection option. Example:
$val = $db->connect_option('RaiseError'); # get
$db->connect_option(AutoCommit => 1); # set
Connection options are name/value pairs that are passed in a hash reference
as the fourth argument to the call to DBI-> connect(). See the
DBI documentation for descriptions of the various options.
- connect_options [HASHREF | PAIRS]
- Get or set the DBI connect options hash. If a reference to a hash is
passed, it replaces the connect options hash. If a series of name/value
pairs are passed, they are added to the connect options hash.
Returns a reference to the connect options has in scalar context, or a list
of name/value pairs in list context.
- dbh [DBH]
- Get or set the DBI database handle connected to the current data source.
If the database handle does not exist or was created in another process or
thread, this method will discard the old database handle (if any) and
dbi_connect will be called to create a new one.
Returns undef if the database handle could not be constructed and connected.
If there is no registered data source for the current "type" and
"domain", a fatal error will occur.
Note: when setting this attribute, you must pass in a DBI database
handle that has the same driver as the object. For example, if the driver
is "mysql" then the DBI database handle must be connected to a
MySQL database. Passing in a mismatched database handle will cause a fatal
error.
- dbi_connect [ARGS]
- This method calls DBI->connect(...), passing all ARGS and returning all
values. This method has no affect on the internal state of the object. Use
the connect method to create and store a new database handle in the
object.
Override this method in your Rose::DB subclass if you want to use a
different method (e.g. DBI-> connect_cached()) to create
database handles.
- disconnect
- Decrements the reference count for the database handle and disconnects it
if the reference count is zero and if the database handle was originally
connected by this object. (This may not be the case if, say, a subclass's
custom implementation of dbi_connect calls DBI's connect_cached method.)
Regardless of the reference count, it sets the dbh attribute to undef.
Returns true if all pre_disconnect_sql statements (if any) were run
successfully and the database handle was disconnected successfully (or if
it was simply set to undef), false otherwise.
The database handle will not be disconnected if any pre_disconnect_sql
statement fails to execute, and the pre_disconnect_sql is not run unless
the handle is going to be disconnected.
- do_transaction CODE [, ARGS]
- Execute arbitrary code within a single transaction, rolling back if any of
the code fails, committing if it succeeds. CODE should be a code
reference. It will be called with any arguments passed to do_transaction
after the code reference. Example:
# Transfer $100 from account id 5 to account id 9
$db->do_transaction(sub
{
my($amt, $id1, $id2) = @_;
my $dbh = $db->dbh or die $db->error;
# Transfer $amt from account id $id1 to account id $id2
$dbh->do("UPDATE acct SET bal = bal - $amt WHERE id = $id1");
$dbh->do("UPDATE acct SET bal = bal + $amt WHERE id = $id2");
},
100, 5, 9) or warn "Transfer failed: ", $db->error;
If the CODE block threw an exception or the transaction could not be started
and committed successfully, then undef is returned and the exception
thrown is available in the error attribute. Otherwise, a true value is
returned.
- error [MSG]
- Get or set the error message associated with the last failure. If a method
fails, check this attribute to get the reason for the failure in the form
of a text message.
- has_dbh
- Returns true if the object has a DBI database handle (dbh), false if it
does not.
- has_primary_key [ TABLE | PARAMS ]
- Returns true if the specified table has a primary key (as determined by
the primary_key_column_names method), false otherwise.
The arguments are the same as those for the primary_key_column_names method:
either a table name or name/value pairs specifying "table",
"catalog", and "schema". The "catalog" and
"schema" parameters are optional and default to the return
values of the catalog and schema methods, respectively. See the
documentation for the primary_key_column_names for more information.
- in_transaction
- Return true if the dbh is currently in the middle of a transaction, false
(but defined) if it is not. If no dbh exists, then undef is returned.
- init_db_info
- Initialize data source configuration information based on the current
values of the type and domain attributes by pulling data from the
corresponding registry entry. If there is no registered data source for
the current type and domain, a fatal error will occur. init_db_info is
called as part of the new and connect methods.
- insertid_param
- Returns the name of the DBI statement handle attribute that contains the
auto-generated unique key created during the last insert operation.
Returns undef if the current data source does not support this
attribute.
- keyword_function_calls [BOOL]
- Get or set a boolean value that indicates whether or not any string that
looks like a function call (matches "/^\w+\(.*\)$/") will be
treated as a "keyword" by the various format_* methods. Defaults
to the value returned by the default_keyword_function_calls class
method.
- last_insertid_from_sth STH
- Given a DBI statement handle, returns the value of the auto-generated
unique key created during the last insert operation. This value may be
undefined if this feature is not supported by the current data
source.
- list_tables
- Returns a list (in list context) or reference to an array (in scalar
context) of tables in the database. The current catalog and schema are
honored.
- quote_column_name NAME
- Returns the column name NAME appropriately quoted for use in an SQL
statement. (Note that "appropriate" quoting may mean no quoting
at all.)
- release_dbh
- Decrements the reference count for the DBI database handle, if it exists.
Returns 0 if the database handle does not exist.
If the reference count drops to zero, the database handle is disconnected.
Keep in mind that the Rose::DB object itself will increment the reference
count when the database handle is connected, and decrement it when
disconnect is called.
Returns true if the reference count is not 0 or if all pre_disconnect_sql
statements (if any) were run successfully and the database handle was
disconnected successfully, false otherwise.
The database handle will not be disconnected if any pre_disconnect_sql
statement fails to execute, and the pre_disconnect_sql is not run unless
the handle is going to be disconnected.
See the "Database Handle Life-Cycle Management" section for more
information on the retain/release system.
- retain_dbh
- Returns the connected DBI database handle after incrementing the reference
count. If the database handle does not exist or is not already connected,
this method will do everything necessary to do so.
Returns undef if the database handle could not be constructed and connected.
If there is no registered data source for the current type and domain, a
fatal error will occur.
See the "Database Handle Life-Cycle Management" section for more
information on the retain/release system.
- rollback
- Roll back the current transaction by calling the rollback method on the
DBI database handle. If the DBI database handle does not exist or is not
connected, 0 is returned.
If the call to DBI's rollback method succeeds or if auto-commit is enabled,
1 is returned. If it fails, undef is returned.
Data Source Configuration¶
Not all databases will use all of these values. Values that are not supported
are simply ignored.
- autocommit [VALUE]
- Get or set the value of the "AutoCommit" connect option and DBI
handle attribute. If a VALUE is passed, it will be set in both the connect
options hash and the current database handle, if any. Returns the value of
the "AutoCommit" attribute of the database handle if it exists,
or the connect option otherwise.
This method should not be mixed with the connect_options method in calls to
register_db or modify_db since connect_options will overwrite all
the connect options with its argument, and neither register_db nor
modify_db guarantee the order that its parameters will be evaluated.
- catalog [CATALOG]
- Get or set the database catalog name. This setting is only relevant to
databases that support the concept of catalogs.
- connect_options [HASHREF | PAIRS]
- Get or set the options passed in a hash reference as the fourth argument
to the call to DBI-> connect(). See the DBI documentation for
descriptions of the various options.
If a reference to a hash is passed, it replaces the connect options hash. If
a series of name/value pairs are passed, they are added to the connect
options hash.
Returns a reference to the hash of options in scalar context, or a list of
name/value pairs in list context.
When init_db_info is called for the first time on an object (either in
isolation or as part of the connect process), the connect options are
merged with the default_connect_options. The defaults are overridden in
the case of a conflict. Example:
Rose::DB->register_db(
domain => 'development',
type => 'main',
driver => 'Pg',
database => 'dev_db',
host => 'localhost',
username => 'devuser',
password => 'mysecret',
connect_options =>
{
RaiseError => 0,
AutoCommit => 0,
}
);
# Rose::DB->default_connect_options are:
#
# AutoCommit => 1,
# ChopBlanks => 1,
# PrintError => 1,
# RaiseError => 1,
# Warn => 0,
# The object's connect options are merged with default options
# since new() will trigger the first call to init_db_info()
# for this object
$db = Rose::DB->new(domain => 'development', type => 'main');
# $db->connect_options are:
#
# AutoCommit => 0,
# ChopBlanks => 1,
# PrintError => 1,
# RaiseError => 0,
# Warn => 0,
$db->connect_options(TraceLevel => 2); # Add an option
# $db->connect_options are now:
#
# AutoCommit => 0,
# ChopBlanks => 1,
# PrintError => 1,
# RaiseError => 0,
# TraceLevel => 2,
# Warn => 0,
# The object's connect options are NOT re-merged with the default
# connect options since this will trigger the second call to
# init_db_info(), not the first
$db->connect or die $db->error;
# $db->connect_options are still:
#
# AutoCommit => 0,
# ChopBlanks => 1,
# PrintError => 1,
# RaiseError => 0,
# TraceLevel => 2,
# Warn => 0,
- database [NAME]
- Get or set the database name used in the construction of the DSN used in
the DBI connect call.
- domain [DOMAIN]
- Get or set the data source domain. See the "Data Source
Abstraction" section for more information on data source
domains.
- driver [DRIVER]
- Get or set the driver name. The driver name can only be set during object
construction (i.e., as an argument to new) since it determines the object
class. After the object is constructed, setting the driver to anything
other than the same value it already has will cause a fatal error.
Even in the call to new, setting the driver name explicitly is not
recommended. Instead, specify the driver when calling register_db for each
data source and allow the driver to be set automatically based on the
domain and type.
The driver names for the currently supported database types are:
pg
mysql
informix
oracle
sqlite
Driver names should only use lowercase letters.
- dsn [DSN]
- Get or set the DBI DSN (Data Source Name) passed to the call to DBI's
connect method.
An attempt is made to parse the new DSN. Any parts successfully extracted
are assigned to the corresponding Rose::DB attributes (e.g., host, port,
database). If no value could be extracted for an attribute, it is set to
undef.
If the DSN is never set explicitly, it is built automatically based on the
relevant object attributes.
If the DSN is set explicitly, but any of host, port, database, schema, or
catalog are also provided, either in an object constructor or when the
data source is registered, the explicit DSN may be ignored as a new DSN is
constructed based on these attributes.
- handle_error [VALUE]
- Get or set the value of the "HandleError" connect option and DBI
handle attribute. If a VALUE is passed, it will be set in both the connect
options hash and the current database handle, if any. Returns the value of
the "HandleError" attribute of the database handle if it exists,
or the connect option otherwise.
This method should not be mixed with the connect_options method in calls to
register_db or modify_db since connect_options will overwrite all
the connect options with its argument, and neither register_db nor
modify_db guarantee the order that its parameters will be evaluated.
- host [NAME]
- Get or set the database server host name used in the construction of the
DSN which is passed in the DBI connect call.
- password [PASS]
- Get or set the password that will be passed to the DBI connect call.
- port [NUM]
- Get or set the database server port number used in the construction of the
DSN which is passed in the DBI connect call.
- pre_disconnect_sql [STATEMENTS]
- Get or set the SQL statements that will be run immediately before
disconnecting from the database. STATEMENTS should be a list or reference
to an array of SQL statements. Returns a reference to the array of SQL
statements in scalar context, or a list of SQL statements in list context.
The SQL statements are run in the order that they are supplied in
STATEMENTS. If any pre_disconnect_sql statement fails when executed, the
subsequent statements are ignored.
- post_connect_sql [STATEMENTS]
- Get or set the SQL statements that will be run immediately after
connecting to the database. STATEMENTS should be a list or reference to an
array of SQL statements. Returns a reference to the array of SQL
statements in scalar context, or a list of SQL statements in list context.
The SQL statements are run in the order that they are supplied in
STATEMENTS. If any post_connect_sql statement fails when executed, the
subsequent statements are ignored.
- primary_key_column_names [ TABLE | PARAMS ]
- Returns a list (in list context) or reference to an array (in scalar
context) of the names of the columns that make up the primary key for the
specified table. If the table has no primary key, an empty list (in list
context) or reference to an empty array (in scalar context) will be
returned.
The table may be specified in two ways. If one argument is passed, it is
taken as the name of the table. Otherwise, name/value pairs are expected.
Valid parameter names are:
- "catalog"
- The name of the catalog that contains the table. This parameter is
optional and defaults to the return value of the catalog method.
- "schema"
- The name of the schema that contains the table. This parameter is optional
and defaults to the return value of the schema method.
- "table"
- The name of the table. This parameter is required.
Case-sensitivity of names is determined by the underlying database. If your
database is case-sensitive, then you must pass names to this method with the
expected case.
- print_error [VALUE]
- Get or set the value of the "PrintError" connect option and DBI
handle attribute. If a VALUE is passed, it will be set in both the connect
options hash and the current database handle, if any. Returns the value of
the "PrintError" attribute of the database handle if it exists,
or the connect option otherwise.
This method should not be mixed with the connect_options method in calls to
register_db or modify_db since connect_options will overwrite all
the connect options with its argument, and neither register_db nor
modify_db guarantee the order that its parameters will be evaluated.
- raise_error [VALUE]
- Get or set the value of the "RaiseError" connect option and DBI
handle attribute. If a VALUE is passed, it will be set in both the connect
options hash and the current database handle, if any. Returns the value of
the "RaiseError" attribute of the database handle if it exists,
or the connect option otherwise.
This method should not be mixed with the connect_options method in calls to
register_db or modify_db since connect_options will overwrite all
the connect options with its argument, and neither register_db nor
modify_db guarantee the order that its parameters will be evaluated.
- schema [SCHEMA]
- Get or set the database schema name. This setting is only useful to
databases that support the concept of schemas (e.g., PostgreSQL).
- server_time_zone [TZ]
- Get or set the time zone used by the database server software. TZ should
be a time zone name that is understood by DateTime::TimeZone. The default
value is "floating".
See the DateTime::TimeZone documentation for acceptable values of TZ.
- type [TYPE]
- Get or set the data source type. See the "Data Source
Abstraction" section for more information on data source types.
- username [NAME]
- Get or set the username that will be passed to the DBI connect call.
- format_bitfield BITS [, SIZE]
- Converts the Bit::Vector object BITS into the appropriate format for the
"bitfield" data type of the current data source. If a SIZE
argument is provided, the bit field will be padded with the appropriate
number of zeros until it is SIZE bits long. If the data source does not
have a native "bit" or "bitfield" data type, a
character data type may be used to store the string of 1s and 0s returned
by the default implementation.
- format_boolean VALUE
- Converts VALUE into the appropriate format for the "boolean"
data type of the current data source. VALUE is simply evaluated in Perl's
scalar context to determine if it's true or false.
- format_date DATETIME
- Converts the DateTime object DATETIME into the appropriate format for the
"date" (month, day, year) data type of the current data
source.
- format_datetime DATETIME
- Converts the DateTime object DATETIME into the appropriate format for the
"datetime" (month, day, year, hour, minute, second) data type of
the current data source.
- format_interval DURATION
- Converts the DateTime::Duration object DURATION into the appropriate
format for the interval (years, months, days, hours, minutes, seconds)
data type of the current data source. If DURATION is undefined, a
DateTime::Duration object, a valid interval keyword (according to
validate_interval_keyword), or if it looks like a function call (matches
"/^\w+\(.*\)$/") and keyword_function_calls is true, then it is
returned unmodified.
- format_time TIMECLOCK
- Converts the Time::Clock object TIMECLOCK into the appropriate format for
the time (hour, minute, second, fractional seconds) data type of the
current data source. Fractional seconds are optional, and the useful
precision may vary depending on the data source.
- format_timestamp DATETIME
- Converts the DateTime object DATETIME into the appropriate format for the
timestamp (month, day, year, hour, minute, second, fractional seconds)
data type of the current data source. Fractional seconds are optional, and
the useful precision may vary depending on the data source.
- format_timestamp_with_time_zone DATETIME
- Converts the DateTime object DATETIME into the appropriate format for the
timestamp with time zone (month, day, year, hour, minute, second,
fractional seconds, time zone) data type of the current data source.
Fractional seconds are optional, and the useful precision may vary
depending on the data source.
- parse_bitfield BITS [, SIZE]
- Parse BITS and return a corresponding Bit::Vector object. If SIZE is not
passed, then it defaults to the number of bits in the parsed bit string.
If BITS is a string of "1"s and "0"s or matches
"/^B'[10]+'$/", then the "1"s and "0"s are
parsed as a binary string.
If BITS is a string of numbers, at least one of which is in the range 2-9,
it is assumed to be a decimal (base 10) number and is converted to a
bitfield as such.
If BITS matches any of these regular expressions:
/^0x/
/^X'.*'$/
/^[0-9a-f]+$/
it is assumed to be a hexadecimal number and is converted to a bitfield as
such.
Otherwise, undef is returned.
- parse_boolean STRING
- Parse STRING and return a boolean value of 1 or 0. STRING should be
formatted according to the data source's native "boolean" data
type. The default implementation accepts 't', 'true', 'y', 'yes', and '1'
values for true, and 'f', 'false', 'n', 'no', and '0' values for false.
If STRING is a valid boolean keyword (according to validate_boolean_keyword)
or if it looks like a function call (matches "/^\w+\(.*\)$/")
and keyword_function_calls is true, then it is returned unmodified.
Returns undef if STRING could not be parsed as a valid "boolean"
value.
- parse_date STRING
- Parse STRING and return a DateTime object. STRING should be formatted
according to the data source's native "date" (month, day, year)
data type.
If STRING is a valid date keyword (according to validate_date_keyword) or if
it looks like a function call (matches "/^\w+\(.*\)$/") and
keyword_function_calls is true, then it is returned unmodified. Returns
undef if STRING could not be parsed as a valid "date"
value.
- parse_datetime STRING
- Parse STRING and return a DateTime object. STRING should be formatted
according to the data source's native "datetime" (month, day,
year, hour, minute, second) data type.
If STRING is a valid datetime keyword (according to
validate_datetime_keyword) or if it looks like a function call (matches
"/^\w+\(.*\)$/") and keyword_function_calls is true, then it is
returned unmodified. Returns undef if STRING could not be parsed as a
valid "datetime" value.
- parse_interval STRING [, MODE]
- Parse STRING and return a DateTime::Duration object. STRING should be
formatted according to the data source's native "interval"
(years, months, days, hours, minutes, seconds) data type.
If STRING is a DateTime::Duration object, a valid interval keyword
(according to validate_interval_keyword), or if it looks like a function
call (matches "/^\w+\(.*\)$/") and keyword_function_calls is
true, then it is returned unmodified. Otherwise, undef is returned if
STRING could not be parsed as a valid "interval" value.
This optional MODE argument determines how math is done on duration objects.
If defined, the "end_of_month" setting for each
DateTime::Duration object created by this column will have its mode set to
MODE. Otherwise, the "end_of_month" parameter will not be passed
to the DateTime::Duration constructor.
Valid modes are "wrap", "limit", and
"preserve". See the documentation for DateTime::Duration for a
full explanation.
- parse_time STRING
- Parse STRING and return a Time::Clock object. STRING should be formatted
according to the data source's native "time" (hour, minute,
second, fractional seconds) data type.
If STRING is a valid time keyword (according to validate_time_keyword) or if
it looks like a function call (matches "/^\w+\(.*\)$/") and
keyword_function_calls is true, then it is returned unmodified. Returns
undef if STRING could not be parsed as a valid "time"
value.
- parse_timestamp STRING
- Parse STRING and return a DateTime object. STRING should be formatted
according to the data source's native "timestamp" (month, day,
year, hour, minute, second, fractional seconds) data type. Fractional
seconds are optional, and the acceptable precision may vary depending on
the data source.
If STRING is a valid timestamp keyword (according to
validate_timestamp_keyword) or if it looks like a function call (matches
"/^\w+\(.*\)$/") and keyword_function_calls is true, then it is
returned unmodified. Returns undef if STRING could not be parsed as a
valid "timestamp" value.
- parse_timestamp_with_time_zone STRING
- Parse STRING and return a DateTime object. STRING should be formatted
according to the data source's native "timestamp with time zone"
(month, day, year, hour, minute, second, fractional seconds, time zone)
data type. Fractional seconds are optional, and the acceptable precision
may vary depending on the data source.
If STRING is a valid timestamp keyword (according to
validate_timestamp_keyword) or if it looks like a function call (matches
"/^\w+\(.*\)$/") and keyword_function_calls is true, then it is
returned unmodified. Returns undef if STRING could not be parsed as a
valid "timestamp with time zone" value.
- validate_boolean_keyword STRING
- Returns true if STRING is a valid keyword for the "boolean" data
type of the current data source, false otherwise. The default
implementation accepts the values "TRUE" and
"FALSE".
- validate_date_keyword STRING
- Returns true if STRING is a valid keyword for the "date" (month,
day, year) data type of the current data source, false otherwise. The
default implementation always returns false.
- validate_datetime_keyword STRING
- Returns true if STRING is a valid keyword for the "datetime"
(month, day, year, hour, minute, second) data type of the current data
source, false otherwise. The default implementation always returns
false.
- validate_interval_keyword STRING
- Returns true if STRING is a valid keyword for the "interval"
(years, months, days, hours, minutes, seconds) data type of the current
data source, false otherwise. The default implementation always returns
false.
- validate_time_keyword STRING
- Returns true if STRING is a valid keyword for the "time" (hour,
minute, second, fractional seconds) data type of the current data source,
false otherwise. The default implementation always returns false.
- validate_timestamp_keyword STRING
- Returns true if STRING is a valid keyword for the "timestamp"
(month, day, year, hour, minute, second, fractional seconds) data type of
the current data source, false otherwise. The default implementation
always returns false.
DEVELOPMENT POLICY¶
The Rose development policy applies to this, and all "Rose::*"
modules. Please install Rose from CPAN and then run ""perldoc
Rose"" for more information.
SUPPORT¶
Any Rose::DB questions or problems can be posted to the Rose::DB::Object mailing
list. (If the volume ever gets high enough, I'll create a separate list for
Rose::DB, but it isn't an issue right now.) To subscribe to the list or view
the archives, go here:
<
http://groups.google.com/group/rose-db-object>
Although the mailing list is the preferred support mechanism, you can also email
the author (see below) or file bugs using the CPAN bug tracking system:
<
http://rt.cpan.org/NoAuth/Bugs.html?Dist=Rose-DB>
There's also a wiki and other resources linked from the Rose project home page:
<
http://rose.googlecode.com>
CONTRIBUTORS¶
Kostas Chatzikokolakis, Peter Karman, Brian Duggan, Lucian Dragus, Ask Bjorn
Hansen, Sergey Leschenko, Ron Savage
AUTHOR¶
John C. Siracusa (siracusa@gmail.com)
LICENSE¶
Copyright (c) 2010 by John C. Siracusa. All rights reserved. This program is
free software; you can redistribute it and/or modify it under the same terms
as Perl itself.