5.13 Altering a Semantic Index

You can use the ALTER INDEX statement with a semantic index.

For a local semantic index, the ALTER INDEX statement applies to a specified partition. The general syntax of the ALTER INDEX command for a semantic index is as follows:

ALTER INDEX <index-name> REBUILD [PARTITION <index-partition-name>]
  [PARAMETERS ('-<action_for_policy> <policy-name>')];

• Rebuilding Content for All Existing Policies in a Semantic Index
  
• Rebuilding to Add Content for a New Policy to a Semantic Index
  
• Rebuilding Content for an Existing Policy from a Semantic Index
  
• Rebuilding to Drop Content for an Existing Policy from a Semantic Index
  

5.13.1 Rebuilding Content for All Existing Policies in a Semantic Index

If the PARAMETERS clause is not included in the ALTER INDEX statement, the content of the semantic index (or index partition) is rebuilt for every policy presently associated with the index. The following are two examples:

ALTER INDEX ArticleIndex REBUILD;
ALTER INDEX ArticleLocalIndex REBUILD PARTITION p1;

5.13.2 Rebuilding to Add Content for a New Policy to a Semantic Index

Using add_policy for <action_for_policy>, you can add content for a new base policy or a dependent policy to a semantic index (or index partition). If a dependent policy is being added and if its base policy is not already a part of the index, then content for the base policy is also added implicitly (by invoking the extractor specified as part of the base policy definition). The following is an example:

ALTER INDEX ArticleIndex REBUILD PARAMETERS ('-add_policy MY_POLICY');

5.13.3 Rebuilding Content for an Existing Policy from a Semantic Index

Using rebuild_policy for <action_for_policy>, you can rebuild the content of the semantic index (or index partition) for an existing policy presently associated with the index. The following is an example:

ALTER INDEX ArticleIndex REBUILD PARAMETERS ('-rebuild_policy MY_POLICY');

5.13.4 Rebuilding to Drop Content for an Existing Policy from a Semantic Index

Using drop_policy for <action_for_policy>, you can drop content corresponding to an existing base policy or a dependent policy from a semantic index (or index partition). Note that dropping the content for a base policy will fail if it is the only policy for the index (or index partition) or if it is used by dependent policies associated with this index (or index partition).

The following example drops the content for a policy from an index:

ALTER INDEX ArticleIndex REBUILD PARAMETERS ('-drop_policy MY_POLICY');