Ingres 9.2 Migration Guide - Actian

DBMS Server EnhancementsAutomatic Storage Structure for New TablesThe storage structure of a base table, when created, is automaticallydetermined based on the syntax used for the CREATE TABLE statement. If theCREATE TABLE statement includes at least a primary key, unique constraint, orreferential (foreign key) constraint, the base table structure is set to B-treeand the usual secondary index is not built.If the table definition includes more than one constraint, it chooses theprimary key constraint over a unique constraint, and the first unique constraintover any referential constraint. For primary key or unique constraints, it alsoadds the UNIQUE_SCOPE=STATEMENT attribute to the base table structure. Adependency is added between the constraint and the base table structure sothat the constraint must be explicitly dropped and re-added if the base tablestructure is modified.This feature improves the initial performance of the table. Previously, all newtables were created with a heap structure, by default.This feature is enabled or disabled in a given DBMS Server by setting theconfiguration parameter table_auto_structure to ON or OFF. The default is ON.146 Migration Guide