About CTXCAT Subindexes and Their Costs

A CTXCAT index contains subindexes that you define as part of your index set. You create a subindex on one or more columns to improve mixed query performance. However, the time Oracle Text takes to create a CTXCAT index depends on its total size, and the total size of a CTXCAT index is directly related to the following factors:

• Total text to be indexed

• Number of subindexes in the index set

• Number of columns in the base table that make up the subindexes

Many component indexes in your index set also degrade the performance of insert, update, and delete operations, because more indexes must be updated.

Because of the added index time and disk space costs for creating a CTXCAT index, before adding it to your index set, carefully consider the query performance benefit that each component index gives your application.

Note: You can use I_ROWID_INDEX_CLAUSE of BASIC_STORAGE to speed up creation of a CTXCAT index. This clause is described in Oracle Text Reference.