When you perform operations in Creating a Vector Index, if IVF_GRAPH and IVF_GRAPH_PQ index algorithms are selected, you need to pre-build and register the center point vector.

Context

The vector index acceleration algorithms IVF_GRAPH and IVF_GRAPH_PQ are suitable for ultra-large-scale computing. These two algorithms allow you to narrow down the query range by dividing a vector space into subspaces through clustering or random sampling. Before pre-build, you need to obtain all center point vectors by clustering or random sampling.

Then, pre-construct and register the center point vectors to create the GRAPH or GRAPH_PQ index and register them with the Elasticsearch cluster. All nodes in the cluster can share the index file. Reuse of the center index among shards can effectively reduce the training overhead and the number of center index queries, improving the write and query performance.

Procedure

On the Clusters page, locate the target cluster, and click Access Kibana in the Operation column.
Click Dev Tools in the navigation tree on the left.

Create a center point index table.

For example, if the created index is named my_dict, number_of_shards of the index must be set to 1. Otherwise, the index cannot be registered.
If you want to use the IVF_GRAPH index, set algorithm of the center point index to GRAPH.
If you want to use the IVF_GRAPH_PQ index, set algorithm of the center point index to GRAPH_PQ.

PUT my_dict 
 { 
   "settings": { 
     "index": { 
       "vector": true 
     }, 
     "number_of_shards": 1, 
     "number_of_replicas": 0 
   }, 
   "mappings": { 
     "properties": { 
       "my_vector": { 
         "type": "vector", 
         "dimension": 2, 
         "indexing": true, 
         "algorithm": "GRAPH", 
         "metric": "euclidean" 
       } 
     } 
   } 
 }

Write the center point vector to the created index.
Write the center point vector obtained through sampling or clustering into the created my_dict index by referring to Importing Vector Data.
Call the registration API.
Register the created my_dict index with a Dict object with a globally unique identifier name (dict_name).
```
PUT _vector/register/my_dict 
 { 
   "dict_name": "my_dict" 
 }
```

Create an IVF_GRAPH or IVF_GRAPH_PQ index.

You do not need to specify the dimension and metric information. Simply specify the registered dictionary name.

PUT my_index 
 { 
   "settings": { 
     "index": { 
       "vector": true 
     } 
   }, 
   "mappings": { 
     "properties": { 
       "my_vector": { 
         "type": "vector", 
         "indexing": true, 
         "algorithm": "IVF_GRAPH", 
         "dict_name": "my_dict", 
         "offload_ivf": false 
       } 
     } 
   } 
 }

**Table 1** Field mappings parameters
Parameter	Description
dict_name	Specifies the name of the depended central point index. The vector dimension and measurement metric of the index are the same as those of the Dict index.
offload_ivf	Unloads the IVF inverted index implemented by the underlying index to Elasticsearch. In this way, the use of non-heap memory and the overhead of write and merge operations are reduced. However, the query performance also deteriorates. You can use the default value. Value: true or false Default value: false

(Optional) Pre-Building and Registering a Center Point Vector

Context

Procedure