Bugzilla::DB::Schema - Abstract database schema for Bugzilla
# Obtain MySQL database schema.
# Do not do this. Use Bugzilla::DB instead.
use Bugzilla::DB::Schema;
my $mysql_schema = new Bugzilla::DB::Schema('Mysql');
# Recommended way to obtain database schema.
use Bugzilla::DB;
my $dbh = Bugzilla->dbh;
my $schema = $dbh->_bz_schema();
# Get the list of tables in the Bugzilla database.
my @tables = $schema->get_table_list();
# Get the SQL statements need to create the bugs table.
my @statements = $schema->get_table_ddl('bugs');
# Get the database-specific SQL data type used to implement
# the abstract data type INT1.
my $db_specific_type = $schema->sql_type('INT1');
This module implements an object-oriented, abstract database schema. It should be considered package-private to the Bugzilla::DB module. That means that CGI scripts should never call any function in this module directly, but should instead rely on methods provided by Bugzilla::DB.
If this is your first time looking at Schema.pm, especially if you are making changes to the database, please take a look at http://www.bugzilla.org/docs/developer.html#sql-schema to learn more about how this integrates into the rest of Bugzilla.
SCHEMA_VERSIONThe 'version' of the internal schema structure. This version number is incremented every time the the fundamental structure of Schema internals changes.
This is NOT changed every time a table or a column is added. This number is incremented only if the internal structures of this Schema would be incompatible with the internal structures of a previous Schema version.
In general, unless you are messing around with serialization and deserialization of the schema, you don't need to worry about this constant.
ABSTRACT_SCHEMAThe abstract database schema structure consists of a hash reference in which each key is the name of a table in the Bugzilla database.
The value for each key is a hash reference containing the keys FIELDS and INDEXES which in turn point to array references containing information on the table's fields and indexes.
A field hash reference should must contain the key TYPE. Optional field keys include PRIMARYKEY, NOTNULL, and DEFAULT.
The INDEXES array reference contains index names and information regarding the index. If the index name points to an array reference, then the index is a regular index and the array contains the indexed columns. If the index name points to a hash reference, then the hash must contain the key FIELDS. It may also contain the key TYPE, which can be used to specify the type of index such as UNIQUE or FULLTEXT.
Bugzilla::DB::Schema supports "foreign keys", a way of saying that "Column X may only contain values from Column Y in Table Z". For example, in Bugzilla, bugs.resolution should only contain values from the resolution.values field.
It does this by adding an additional item to a column, called REFERENCES. This is a hash with the following members:
TABLEThe table the foreign key points at
COLUMNThe column pointed at in that table.
DELETEWhat to do if the row in the parent table is deleted. Choices are RESTRICT, CASCADE, or SET NULL.
RESTRICT means the deletion of the row in the parent table will be forbidden by the database if there is a row in this table that still refers to it. This is the default, if you don't specify DELETE.
CASCADE means that this row will be deleted along with that row.
SET NULL means that the column will be set to NULL when the parent row is deleted. Note that this is only valid if the column can actually be set to NULL. (That is, the column isn't NOT NULL.)
UPDATEWhat to do if the value in the parent table is updated. You can set this to CASCADE or RESTRICT, which mean the same thing as they do for "DELETE". This variable defaults to CASCADE, which means "also update this column in this table."
Note: Methods which can be implemented generically for all DBs are implemented in this module. If needed, they can be overridden with DB-specific code in a subclass. Methods which are prefixed with _ are considered protected. Subclasses may override these methods, but other modules should not invoke these methods directly.
new Description: Public constructor method used to instantiate objects of this
class. However, it also can be used as a factory method to
instantiate database-specific subclasses when an optional
driver argument is supplied.
Parameters: $driver (optional) - Used to specify the type of database.
This routine C<die>s if no subclass is found for the specified
driver.
$schema (optional) - A reference to a hash. Callers external
to this package should never use this parameter.
Returns: new instance of the Schema class or a database-specific subclass
_initialize Description: Protected method that initializes an object after
instantiation with the abstract schema. All subclasses should
override this method. The typical subclass implementation
should first call the C<_initialize> method of the superclass,
then do any database-specific initialization (especially
define the database-specific implementation of the all
abstract data types), and then call the C<_adjust_schema>
method.
Parameters: $abstract_schema (optional) - A reference to a hash. If
provided, this hash will be used as the internal
representation of the abstract schema instead of our
default abstract schema. This is intended for internal
use only by deserialize_abstract.
Returns: the instance of the Schema class
_adjust_schema Description: Protected method that alters the abstract schema at
instantiation-time to be database-specific. It is a generic
enough routine that it can be defined here in the base class.
It takes the abstract schema and replaces the abstract data
types with database-specific data types.
Parameters: none
Returns: the instance of the Schema class
get_type_ddlPublic method to convert abstract (database-generic) field specifiers to database-specific data types suitable for use in a CREATE TABLE or ALTER TABLE SQL statment. If no database-specific field type has been defined for the given field type, then it will just return the same field type.
$def - A reference to a hash of a field containing the following keys: TYPE (required), NOTNULL (optional), DEFAULT (optional), PRIMARYKEY (optional), REFERENCES (optional)A DDL string suitable for describing a field in a CREATE TABLE or ALTER TABLE SQL statement
_get_fk_ddlProtected method. Translates the REFERENCES item of a column into SQL.
$table - The name of the table the reference is from.$column - The name of the column the reference is from$references - The REFERENCES hashref from a column.SQL for to define the foreign key, or an empty string if $references is undefined.
convert_typeConverts a TYPE from the "ABSTRACT_SCHEMA" format into the real SQL type.
get_column($table, $column) Description: Public method to get the abstract definition of a column.
Parameters: $table - the table name
$column - a column in the table
Returns: a hashref containing information about the column, including its
type (C<TYPE>), whether or not it can be null (C<NOTNULL>),
its default value if it has one (C<DEFAULT), etc.
Returns undef if the table or column does not exist.
get_table_list Description: Public method for discovering what tables should exist in the
Bugzilla database.
Parameters: none
Returns: An array of table names, in alphabetical order.
get_table_columns Description: Public method for discovering what columns are in a given
table in the Bugzilla database.
Parameters: $table - the table name
Returns: array of column names
get_table_ddl Description: Public method to generate the SQL statements needed to create
the a given table and its indexes in the Bugzilla database.
Subclasses may override or extend this method, if needed, but
subclasses probably should override C<_get_create_table_ddl>
or C<_get_create_index_ddl> instead.
Parameters: $table - the table name
Returns: an array of strings containing SQL statements
_get_create_table_ddl Description: Protected method to generate the "create table" SQL statement
for a given table.
Parameters: $table - the table name
Returns: a string containing the DDL statement for the specified table
_get_create_index_ddl Description: Protected method to generate a "create index" SQL statement
for a given table and index.
Parameters: $table_name - the name of the table
$index_name - the name of the index
$index_fields - a reference to an array of field names
$index_type (optional) - specify type of index (e.g., UNIQUE)
Returns: a string containing the DDL statement
get_add_column_ddl($table, $column, \%definition, $init_value) Description: Generate SQL to add a column to a table.
Params: $table - The table containing the column.
$column - The name of the column being added.
\%definition - The new definition for the column,
in standard C<ABSTRACT_SCHEMA> format.
$init_value - (optional) An initial value to set
the column to. Should already be SQL-quoted
if necessary.
Returns: An array of SQL statements.
get_add_index_ddl Description: Gets SQL for creating an index.
NOTE: Subclasses should not override this function. Instead,
if they need to specify a custom CREATE INDEX statement,
they should override C<_get_create_index_ddl>
Params: $table - The name of the table the index will be on.
$name - The name of the new index.
$definition - An index definition. Either a hashref
with FIELDS and TYPE or an arrayref
containing a list of columns.
Returns: An array of SQL statements that will create the
requested index.
get_alter_column_ddl($table, $column, \%definition) Description: Generate SQL to alter a column in a table.
The column that you are altering must exist,
and the table that it lives in must exist.
Params: $table - The table containing the column.
$column - The name of the column being changed.
\%definition - The new definition for the column,
in standard C<ABSTRACT_SCHEMA> format.
$set_nulls_to - A value to set NULL values to, if
your new definition is NOT NULL and contains
no DEFAULT, and when there is a possibility
that the column could contain NULLs. $set_nulls_to
should be already SQL-quoted if necessary.
Returns: An array of SQL statements.
get_drop_index_ddl($table, $name) Description: Generates SQL statements to drop an index.
Params: $table - The table the index is on.
$name - The name of the index being dropped.
Returns: An array of SQL statements.
get_drop_column_ddl($table, $column) Description: Generate SQL to drop a column from a table.
Params: $table - The table containing the column.
$column - The name of the column being dropped.
Returns: An array of SQL statements.
get_drop_table_ddl($table)Description: Generate SQL to drop a table from the database. Params: $table - The name of the table to drop. Returns: An array of SQL statements.
get_rename_column_ddl($table, $old_name, $new_name) Description: Generate SQL to change the name of a column in a table.
NOTE: ANSI SQL contains no simple way to rename a column,
so this function is ABSTRACT and must be implemented
by subclasses.
Params: $table - The table containing the column to be renamed.
$old_name - The name of the column being renamed.
$new_name - The name the column is changing to.
Returns: An array of SQL statements.
get_rename_table_sqlGets SQL to rename a table in the database.
$old_name - The current name of the table.$new_name - The new name of the table.delete_table($name) Description: Deletes a table from this Schema object.
Dies if you try to delete a table that doesn't exist.
Params: $name - The name of the table to delete.
Returns: nothing
get_column_abstract($table, $column) Description: A column definition from the abstract internal schema.
cross-database format.
Params: $table - The name of the table
$column - The name of the column that you want
Returns: A hash reference. For the format, see the docs for
C<ABSTRACT_SCHEMA>.
Returns undef if the column or table does not exist.
get_indexes_on_column_abstract($table, $column) Description: Gets a list of indexes that are on a given column.
Params: $table - The table the column is on.
$column - The name of the column.
Returns: Indexes in the standard format of an INDEX
entry on a table. That is, key-value pairs
where the key is the index name and the value
is the index definition.
If there are no indexes on that column, we return
undef.
get_index_abstract($table, $index) Description: Returns an index definition from the internal abstract schema.
Params: $table - The table the index is on.
$index - The name of the index.
Returns: A hash reference representing an index definition.
See the C<ABSTRACT_SCHEMA> docs for details.
Returns undef if the index does not exist.
get_table_abstract($table) Description: Gets the abstract definition for a table in this Schema
object.
Params: $table - The name of the table you want a definition for.
Returns: An abstract table definition, or undef if the table doesn't
exist.
add_table($name, \%definition) Description: Creates a new table in this Schema object.
If you do not specify a definition, we will
simply create an empty table.
Params: $name - The name for the new table.
\%definition (optional) - An abstract definition for
the new table.
Returns: nothing
rename_tableRenames a table from $old_name to $new_name in this Schema object.
delete_column($table, $column) Description: Deletes a column from this Schema object.
Params: $table - Name of the table that the column is in.
The table must exist, or we will fail.
$column - Name of the column to delete.
Returns: nothing
rename_column($table, $old_name, $new_name) Description: Renames a column on a table in the Schema object.
The column that you are renaming must exist.
Params: $table - The table the column is on.
$old_name - The current name of the column.
$new_name - The new name of hte column.
Returns: nothing
set_column($table, $column, \%new_def) Description: Changes the definition of a column in this Schema object.
If the column doesn't exist, it will be added.
The table that you specify must already exist in the Schema.
NOTE: This does not affect the database on the disk.
Use the C<Bugzilla::DB> "Schema Modification Methods"
if you want to do that.
Params: $table - The name of the table that the column is on.
$column - The name of the column.
\%new_def - The new definition for the column, in
C<ABSTRACT_SCHEMA> format.
Returns: nothing
set_fk($table, $column \%fk_def)Sets the REFERENCES item on the specified column.
set_index($table, $name, $definition) Description: Changes the definition of an index in this Schema object.
If the index doesn't exist, it will be added.
The table that you specify must already exist in the Schema.
NOTE: This does not affect the database on the disk.
Use the C<Bugzilla::DB> "Schema Modification Methods"
if you want to do that.
Params: $table - The table the index is on.
$name - The name of the index.
$definition - A hashref or an arrayref. An index
definition in C<ABSTRACT_SCHEMA> format.
Returns: nothing
delete_index($table, $name) Description: Removes an index definition from this Schema object.
If the index doesn't exist, we will fail.
The table that you specify must exist in the Schema.
NOTE: This does not affect the database on the disk.
Use the C<Bugzilla::DB> "Schema Modification Methods"
if you want to do that.
Params: $table - The table the index is on.
$name - The name of the index that we're removing.
Returns: nothing
columns_equal($col_one, $col_two) Description: Tells you if two columns have entirely identical definitions.
The TYPE field's value will be compared case-insensitive.
However, all other fields will be case-sensitive.
Params: $col_one, $col_two - The columns to compare. Hash
references, in C<ABSTRACT_SCHEMA> format.
Returns: C<1> if the columns are identical, C<0> if they are not.
serialize_abstract() Description: Serializes the "abstract" schema into a format
that deserialize_abstract() can read in. This is
a method, called on a Schema instance.
Parameters: none
Returns: A scalar containing the serialized, abstract schema.
Do not attempt to manipulate this data directly,
as the format may change at any time in the future.
The only thing you should do with the returned value
is either store it somewhere (coupled with appropriate
SCHEMA_VERSION) or deserialize it.
deserialize_abstract($serialized, $version) Description: Used for when you've read a serialized Schema off the disk,
and you want a Schema object that represents that data.
Params: $serialized - scalar. The serialized data.
$version - A number. The "version"
of the Schema that did the serialization.
See the docs for C<SCHEMA_VERSION> for more details.
Returns: A Schema object. It will have the methods of (and work
in the same fashion as) the current version of Schema.
However, it will represent the serialized data instead of
ABSTRACT_SCHEMA.
These methods are generally called on the class instead of on a specific object.
get_empty_schema() Description: Returns a Schema that has no tables. In effect, this
Schema is totally "empty."
Params: none
Returns: A "empty" Schema object.
The size and range data provided here is only intended as a guide. See your database's Bugzilla module (in this directory) for the most up-to-date values for these data types. The following abstract data types are used:
BOOLEANLogical value 0 or 1 where 1 is true, 0 is false.
INT1Integer values (-128 - 127 or 0 - 255 unsigned).
INT2Integer values (-32,768 - 32767 or 0 - 65,535 unsigned).
INT3Integer values (-8,388,608 - 8,388,607 or 0 - 16,777,215 unsigned)
INT4Integer values (-2,147,483,648 - 2,147,483,647 or 0 - 4,294,967,295 unsigned)
SMALLSERIALAn auto-increment "INT2"
MEDIUMSERIALAn auto-increment "INT3"
INTSERIALAn auto-increment "INT4"
TINYTEXTVariable length string of characters up to 255 (2^8 - 1) characters wide.
MEDIUMTEXTVariable length string of characters up to 4000 characters wide. May be longer on some databases.
LONGTEXTVariable length string of characters up to 16M (2^24 - 1) characters wide.
LONGBLOBVariable length string of binary data up to 4M (2^32 - 1) bytes wide
DATETIMEDATETIME support varies from database to database, however, it's generally safe to say that DATETIME entries support all date/time combinations greater than 1900-01-01 00:00:00. Note that the format used is YYYY-MM-DD hh:mm:ss to be safe, though it's possible that your database may not require leading zeros. For greatest compatibility, however, please make sure dates are formatted as above for queries to guarantee consistent results.
Database-specific subclasses should define the implementation for these data types as a hash reference stored internally in the schema object as db_specific. This is typically done in overridden _initialize method.
The following abstract boolean values should also be defined on a database-specific basis:
TRUEFALSEhttp://www.bugzilla.org/docs/developer.html#sql-schema