Bentley Systems, Incorporated
Maintaining a class hierarchy of an object-oriented data model using shared columns and/or overflow tables

Abstract:

Techniques are provided for maintaining a class hierarchy of an object-oriented data model in tables of a relational database that minimize performance impact (e.g., in terms of both processing resources and storage footprint). In one embodiment, an object-relational mapping system accesses a class hierarchy of an object-oriented data model. A plurality of tables of a relational database are generated, including a primary table, a joined table and an overflow table. The object-relational mapping system maps classes of the class hierarchy to the primary table, joined table and overflow table, wherein the mapping maps properties of classes to columns of the primary table and joined table until a column threshold is reached and then maps excess properties to columns of the overflow table, and the mapping shares at least one column of the primary table, joined table or overflow table among classes such that multiple different properties are mapped to the shared column. The properties of the classes are stored to the plurality of tables according to the mapping.