Text search index creation
A text search index is a compilation of significant terms extracted from text documents. Each term is associated with the document from which it was extracted.
You create a text search index once for each column that contains
text to be searched. When you create a text search index, you also
create the following objects:
- A staging table
- This keeps track of all changed rows in the user table.
- An auxiliary staging table (optional)
- This keeps track of inserts and updates in the user table via integrity processing.
- An event table
- This collects information about the status of an update index command or any errors encountered during its processing. If errors occur during indexing, index update events are added to the event table.
- Triggers on the user table
- These add information to the staging table whenever a document
in the column is added, deleted, or changed. The information is necessary
for index synchronization when indexing time next occurs. Note: If you use the LOAD command to populate your documents, triggers are not activated, and incremental indexing of the loaded documents will not work. Instead, use the IMPORT command, which does activate triggers. Alternatively you can add the auxiliary infrastructure for integrity processing, this will recognize changes for example, with the LOAD INSERT command.
After you create a text search index, it is empty and, therefore, not searchable, until you update it. When creating the text search index, you can specify a frequency which is used by the scheduler to check periodically whether an update of the text search index is required and that the update command is to be run if necessary.