|
DBIx::SystemCatalog - Perl module for accessing system catalog in common databases |
DBIx::SystemCatalog - Perl module for accessing system catalog in common databases (access through DBI(3))
use DBI;
use DBIx::SystemCatalog;
# create DBIx::SystemCatalog object and bind DBI
my $dbh = DBI->connect('dbi:Oracle:','login','password');
my $catalog = new DBIx::SystemCatalog $dbh;
# fetch all database schemas
my @schemas = $catalog->schemas;
# select one schema (e.g. first schema)
$catalog->schema($schemas[0]);
# fetch all tables and views with types of objects
my @tables = $catalog->tables_with_types;
# fetch columns of first fetched table
my @columns = $catalog->table_columns($tables[0]->{name});
# fetch all relationships between tables and views
my @relationships = $catalog->relationships;
# fetch all primary keys for table
my @primary_keys = $catalog->primary_keys($tables[0]->{name});
# fetch all unique indexes for table
my @unique_indexes = $catalog->unique_indexes($tables[0]->{name});
# fetch all indexes for table
my @indexes = $catalog->indexes($table[0]->{name});
# disconnect database
$dbh->disconnect;
This module can access to system catalog of database through DBI(3) interface.
Basic methods access to objects through standard DBI(3) interface
(call tables() for list of objects and selectall_arrayref() with basic
SQL to get structure of objects).
Constructor looks for specific module implemented database interface for used DBD driver (obtained from DBI(3)). These module can add faster and better functions such as relationships or types of objects.
Constructor create instance of this class and bind DBI(3) connection.
Then obtain used driver name from DBI(3) class and look for descendant
of this class for this driver (e.g. DBIx::SystemCatalog::Oracle module
for Oracle driver). If success, return instance of this more specific class,
otherwise return itself.
You must passed connected DBI(3) instance as first argument to constructor
and you can't disconnect that instance while you use this instance of
DBIx::SystemCatalog.
$catalog = new DBIx::SystemCatalog $dbh
Because new() is quite complicated, descendant inherits this new()
constructor and redefine init() constructor which is called from new().
init() gets all arguments from new() with one exception - instead of
name of class this constructor get instance of object.
Constructor must return true value to make successful of creating instance
of object. In this base class is init() abstract, always true.
This method isn't called directly from user.
Method must return list of schemas from database. In this base class method
always return empty list, because standard DBI(3) method can't get list of
schemas.
my @schemas = $catalog->schemas()
Method set current schema name. Other methods work only with this schema. Because working with one schema is typical work, all methods in specific class need this schema name. Method can set schema (descendant need not redefine it).
$catalog->schema('IS')
Method must return list of storage objects from database (mean tables and
views). In this base class method use DBI(3) function tables() for
fetching this list. Specific class ussually redefine method for faster
access and return all objects (list of views is in DBI(3) functions
uncertain).
my @tables = $catalog->tables()
Method return list of names of constants SC_TYPE_*.
my @types = $catalog->sc_types()
Method must return list of columns for object in argument (table or view). In this base class method use SQL query
SELECT * FROM object WHERE 0 = 1
and fetch names of returned columns. Specific class can redefine method for faster access.
In future this method (or similar extended method) return more details about columns. This feature must add specific class. API for returned values are not still specified.
my @columns = $catalog->table_column('USERS')
Method return constant SC_TYPE_* according to type of object passed
as argument (table or view). In this base class method return
SC_TYPE_UNKNOWN. Specific class ussually redefine method for correct
result.
my $type = $catalog->table_type('USERS')
Method combine tables() and table_type() and return list of hashes
with keys name (table name) and type (same meaning as returned value
from table_type()). Base class implement this method as tables() and
for each table call table_type(). Specific class ussually redefine it for
faster access.
for my $object ($catalog->tables_with_types()) {
my $name = $object->{name};
my $type = $object->{type};
}
Method return list of all relationships in schema. Each item in list is hash with keys:
table (table name) and
column (column name). I think all table will be same as from_table key
in returning hash, but only God know true.
from_columns item of returning hash.
Base class don't implement this method (return empty list), but specific class can redefine it (for database which support foreign keys or another form of relationships).
for my $relationship ($catalog->relationships()) {
for (%$relationship) {
print "$_: ";
if (ref $relationship{$_}) {
print join ',',@{$relationship{$_}};
} else {
print $relationship{$_};
}
print "\n";
}
}
Method return list of all columns which are primary keys of specified table.
my @primary_keys = $catalog->primary_keys($tablename);
Method return list of all columns which contain unique indexes of specified table. Returns list of lists.
my @unique_indexes = $catalog->unique_indexes($tablename);
Method return list of all columns which contain indexes of specified table. Returns list of lists.
my @indexes = $catalog->indexes($tablename);
Emulating filesystem for dbsh - method must return list of names according to CWD. All items ended by / are directories. We must return ../ in subdirectories.
Standard module produce next structure:
/Schema
/Schema/Tables
/Schema/Views
and generate tables and views (or unknown table objects) into this structure.
my @files = $catalog->fs_ls('/');
I currently support only Oracle and Pg (PostgreSQL) specific class. Returned API is described in this man page. I think man pages for specific classes we don't need because functions are described in this man page.
If you want contribute another specific class, please mail me.
Support for mySQL database, fetching detailed structure of tables, fetching definition of views, stored procedures and functions, fetching other objects and their specific properties.
0.06
(c) 2001 Milan Sorm, sorm@pef.mendelu.cz at Faculty of Economics, Mendel University of Agriculture and Forestry in Brno, Czech Republic.
This module was needed for making SchemaView Plus (svplus) for fetching
schema structure and relationships between objects in schema.
perl(1), DBI(3), svplus(1).
|
DBIx::SystemCatalog - Perl module for accessing system catalog in common databases |