ALTER INDEX

Purpose

To make changes to hybrid vector indexes.

Syntax

ALTER INDEX [schema.]index_name REBUILD 
  PARAMETERS(
      ['UPDATE VECTOR INDEX [VECTOR_IDXTYPE HNSW/IVF]']
      ['REPLACE vectorizer vectorizer_pref_name']
      )
  [PARALLEL n];

Note:

If you do not specify the PARAMETERS clause, then all parts of the hybrid vector index (both Oracle Text index and vector index) are recreated with existing preference settings.
Renaming hybrid vector indexes using the ALTER INDEX RENAME syntax is not supported.
The ALTER INDEX parameter UDPATE VECTOR INDEX is not supported for Local HVI and HNSW vector indexes.

[schema.]index_name

Specifies name of the hybrid vector index that you want to modify.

PARAMETERS(UPDATE VECTOR INDEX)

Rebuilds both text part and vector part of the hybrid vector index. For text part, the rebuild uses the preferences which are specified during the index creation or the default preferences if not specified. For the vector part (chunking, embedding and vector index creation), rebuild uses the new vectorizer preference specified in the ALTER INDEX REBUILD syntax. See CREATE HYBRID VECTOR INDEX for detailed information on the preferences set during the index creation.

PARAMETERS(REPLACE vectorizer vectorizer_pref_name)

Recreates only the vector index part of a hybrid vector index with the specified vectorizer preference settings.

Note:

For non HVI index, replace operation would throw an error, as it cannot replace something that was not present.

PARALLEL

Specifies parallel indexing, as described for the CREATE HYBRID VECTOR INDEX statement.

For detailed information on the PARALLEL clause, see CREATE HYBRID VECTOR INDEX.

Examples

Here are some examples on how you can modify existing hybrid vector indexes:

To rebuild all parts of a hybrid vector index:

Use the following syntax to rebuild all parts of a hybrid vector index (both Oracle Text index and vector index) with the original preference settings:

Syntax:

ALTER INDEX index_name REBUILD [PARALLEL n];

Note that you do not need to specify any PARAMETERS clause when rebuilding both parts of a hybrid vector index.

Example:

ALTER INDEX my_hybrid_idx REBUILD;

SELECT (select id from doc_table where rowid = jt.doc_rowid) as doc,
       jt.chunk
FROM JSON_TABLE(
         DBMS_HYBRID_VECTOR.SEARCH(
           json(
             '{ "hybrid_index_name" : "my_hybrid_idx",
                "vector" : 
                 { "search_text"    : "vector based search capabilities",
                   "search_mode"    : "CHUNK"
                 },
                "return" : 
                 { "topN"           : 10 }
             }')
           ),
           '$[*]' COLUMNS doc_rowid  PATH '$.rowid',
                          chunk      PATH '$.chunk_text') jt;

To rebuild only the vector index part:

Use the following syntax to rebuild only the vector index part of a hybrid vector index with the original preference settings:

Syntax:

ALTER INDEX index_name REBUILD 
  PARAMETERS('UPDATE VECTOR INDEX') [PARALLEL n];

Example:

ALTER INDEX my_hybrid_idx REBUILD 
  PARAMETERS('UPDATE VECTOR INDEX') PARALLEL 3;

SELECT (select id from doc_table where rowid = jt.doc_rowid) as doc,
       jt.chunk
FROM JSON_TABLE(
         DBMS_HYBRID_VECTOR.SEARCH(
           json(
             '{ "hybrid_index_name" : "my_hybrid_idx",
                "vector" : 
                 { "search_text"    : "vector based search capabilities",
                   "search_mode"    : "CHUNK"
                 },
                "return" : 
                 { "topN"           : 10 }
             }')
           ),
           '$[*]' COLUMNS doc_rowid  PATH '$.rowid',
                          chunk      PATH '$.chunk_text') jt;

To recreate indexes with a vectorizer preference:

You can create a vectorizer preference using the DBMS_VECTOR_CHAIN.CREATE_PREFERENCE PL/SQL function. For detailed information on how to create a vectorizer preference, see CREATE_PREFERENCE. After creating the preference, use the REPLACE vectorizer parameter to pass the preference name here.

Syntax:
```
ALTER INDEX index_name REBUILD 
  parameters('REPLACE vectorizer vectorizer_pref_name') [PARALLEL n];
```
Note:
For non-HVI index, the REPLACE operation would throw an error.

Example:
```
ALTER INDEX my_hybrid_idx REBUILD 
  parameters('REPLACE vectorizer my_vectorizer_pref') [PARALLEL n];
```
To replace only the model and/or vector index type

For an existing HVI index, you can replace the model and/or the index type without specifying the full vectorizer preference using the following syntax.

Syntax:
```
ALTER INDEX schema.index_name REBUILD[
parameters('REPLACE MODEL model_name VECTOR_IDXTYPE hnsw/ivf')];
```
Example:
```
ALTER INDEX schema.my_hybrid_idx REBUILD[
parameters('REPLACE MODEL my_model_name VECTOR_IDXTYPE ivf')];
```
Note:
For non HVI indexes, this syntax would throw an error. If a vectorizer is also specified alongside the model and/or vector_idxtype, it would lead to an error, as only one of either vectorizer or model/vector_idxtype is allowed.