Relational databases.

摘要

A plurality of packed descriptions is provided as a column in a table each entry containing data defining attributes associated with a different object (such as a table or view defined to the database) and all its component objects (such as related columns and indexes). Accessing the row corresponding to a particular object returns a description of all of the attributes of the object's component objects, as well as information describing the object itself. The packed description information is redundantly stored conventionally in other system catalogs for use IN at IN querying physical definitions of objects in a manner consistent with other database products. The database state information comprising the packed descriptions is retained in internal format whereas the correlative redundant information is in a user-readable external format. By denormalising the schema for schema data whereby identifying relationships between objects is simplified, time required for compilation of statements referencing objects is substantially reduced. All information concerning attributes of an object specified in statement and its component objects necessary to compile the statement may thereby be fetched from the packed description field corresponding to the object in one I/O operation. Objects' descriptions must otherwise be retrieved from numerous I/Os to separate system catalogs and rows collectively containing the descriptions.