Milan Sorm > SchemaView-Plus > DBIx::SystemCatalog

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Module Version: 0.06   Source  

NAME ^

DBIx::SystemCatalog - Perl module for accessing system catalog in common databases (access through DBI(3))

SYNOPSIS ^

        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;

DESCRIPTION ^

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.

CONSTANTS ^

Type of object

SC_TYPE_UNKNOWN
SC_TYPE_TABLE
SC_TYPE_VIEW

THE DBIx::SystemCatalog CLASS ^

new (DBI)

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

init

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.

schemas

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()

schema (NAME)

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')

tables

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()

sc_types

Method return list of names of constants SC_TYPE_*.

        my @types = $catalog->sc_types()

table_columns (OBJECT)

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')

table_type (OBJECT)

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')

tables_with_types

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};
        }

relationships

Method return list of all relationships in schema. Each item in list is hash with keys:

name

Name of relationship

from_table

Name of source table with foreign key

to_table

Name of destination table with reference for foreign key

from_columns

List of source columns, each item is hash with key 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.

to_columns

List of destination columns, each item has same structure as items in 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";
                }
        }

primary_keys

Method return list of all columns which are primary keys of specified table.

        my @primary_keys = $catalog->primary_keys($tablename);

unique_indexes

Method return list of all columns which contain unique indexes of specified table. Returns list of lists.

        my @unique_indexes = $catalog->unique_indexes($tablename);

indexes

Method return list of all columns which contain indexes of specified table. Returns list of lists.

        my @indexes = $catalog->indexes($tablename);

fs_ls CWD

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('/');

SPECIFIC CLASSES ^

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.

TODO ^

Support for mySQL database, fetching detailed structure of tables, fetching definition of views, stored procedures and functions, fetching other objects and their specific properties.

VERSION ^

0.06

AUTHOR ^

(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.

SEE ALSO ^

perl(1), DBI(3), svplus(1).

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