Schema

Schema encapsulates a data structure representing databases and tables.  Although in MySQL “schema” is technically equivalent to “databae”, we use “schema” loosely to mean a collection of schema objects: databases, tables, and columns.  These objects are organized in a hash keyed on database and table names.  The hash is called schema and looks like,

  db1 => {
     tbl1 => {
        db         => 'db1',
        tbl        => 'tbl1',
        tbl_struct => <TableParser::parse()>
        ddl        => "CREATE TABLE `tbl` ( ...",
     }
  }
(stop code)
Each table has at least a db and tbl key and probably a tbl_struct.

The important thing about a Schema object is that it should be the only
data structure with this data, and other modules should reference and add
data to it rather than creating other similar copies.  <ColumnMap> does
this for example.

The other important thing about a Schema object is that the data structure
is the standard.  Other modules should take db or tbl hashrefs pointing
into the data structure.  Tbl hashrefs should always have at least at db
and tbl key (which is redundant but necessary so that each tbl hashref
includes its own database and table name).

Schema objects are usually added by a <SchemaIterator>, but you can add
them manually if needed; see <add_schema_object()>.