5.4.4 Notation-correction-search text-index specification (CORRECTIONRULE)
To use correction search, define a text index that supports correction search. For details about correction search, see 2.17.1 Correction search.
If you define a text index that supports correction search, you can reduce the number of pages to be loaded when you perform the following search operations. This improves table retrieval performance.
-
Perform correction search by specifying the scalar function CONTAINS.
-
Use a regular expression to perform case-insensitive search by specifying IGNORECASE (or I) for FLAG in the LIKE_REGEX predicate.
To define a text index that supports correction search, you specify CORRECTIONRULE (notation-correction-search text-index specification) in a CREATE INDEX statement.
Note that the index data in a text index that supports correction search is larger than the index data in an ordinary text index. Therefore, before you define a text index, obtain the size of index data, and confirm that you can define a text index without problems. For details, see 5.8.5 Determining the number of storage pages for each text index segment.
- Important
-
If the character encoding used on the HADB server is Shift-JIS (that is, the value specified for the environment variable ADBLANG is SJIS), you cannot define a text index that supports correction search.
A text index that supports correction search can also be used as an ordinary text index.