{"id":8065,"date":"2020-01-20T22:29:32","date_gmt":"2020-01-21T06:29:32","guid":{"rendered":"https:\/\/www.couchbase.com\/blog\/?p=8065"},"modified":"2025-06-13T17:21:51","modified_gmt":"2025-06-14T00:21:51","slug":"couchbase-6-5-rms-for-indexing-service","status":"publish","type":"post","link":"https:\/\/www.couchbase.com\/blog\/couchbase-6-5-rms-for-indexing-service\/","title":{"rendered":"Couchbase 6.5 – RMS for Indexing Service"},"content":{"rendered":"

Couchbase 6.5 release includes an extensive list of Enterprise Grade Database Query capability that allows customers to expand the adoption of NoSQL database into traditional database applications. The release has added transactional capability, Analytical Window functions, user defined JS functions, as well as Index Advisor to improve query performance.\u00a0 As performance is one of the most important aspects of the Couchbase platform, the new release also includes a set of new enhancements to further strengthen the Couchbase Index Service and improve operational efficiency. These features are grouped together under the general heading of Reliability, Manageability, and Serviceability – Index Service RMS.<\/span><\/p>\n

1. ALTER INDEX to change index replica count<\/span><\/h4>\n

In 6.5.0, we have added the much asked-for support for changing the number of replicas for an index using the ALTER INDEX command. The replica count can be changed using ALTER command as in below example –<\/span><\/p>\n

ALTER INDEX `travel-sample`.airlines_idx WITH {\"action\":\"replica_count\",\"num_replica\": 3}'\r\n<\/pre>\n
action<\/strong><\/em> for ALTER INDEX is <\/span>replica_count<\/b> and the parameter <\/span>num_replica<\/b> specifies the new number of replicas for the index. If num_replica value in the ALTER statement is greater than the current count of replicas, additional replicas are created; if it is lesser than current replica count, replicas are removed.\u00a0<\/span><\/p>\n
2. ALTER INDEX to drop an index replica<\/span><\/h4>\n
ALTER INDEX command has further been enhanced to drop an individual index replica using syntax as below:<\/span><\/p>\n
ALTER INDEX `travel-sample`.airlines_idx WITH {\"action\":\"drop_replica\",\"replicaId\": 2}'<\/pre>\n
action<\/strong><\/em> is <\/span>drop_index<\/b> and <\/span>replicaId<\/b> is the ID of the replica which is a number identifying a replica. The replicaId of a replica and host it resides in can be obtained from REST API getIndexStatus.<\/span><\/p>\n
What are the benefits: Better manageability of index replicas – easier way to increase\/decrease replica count or drop a specific index replica. Find more information at:<\/span><\/p>\n
https:\/\/docs.couchbase.com\/server\/6.5\/n1ql\/n1ql-language-reference\/alterindex.html<\/span><\/a><\/p>\n
3. Improve DCP Rollback handling<\/span><\/h4>\n
DCP rollback happens in the index service when one of the data node gets failed over, and a data replica gets promoted to active. Not every failover leads to rollback. This situation only happens when the index service has more data\/recent vbuuid than the data replica before failover. If the data replica becomes active after a failover, the index service will receive a rollback. Please refer to the DCP documentation<\/span><\/a> for more details. In worst case scenario, DCP could ask index service to rollback to 0.<\/p>\n
With this enhancement, DCP rollback handling for the index service has been made more robust.
\nWhen the index service receives a DCP rollback to 0, it will try to revert to its most current index snapshots, instead of rebuilding the entire index.<\/p>\n
What are the benefits:\u00a0<\/span><\/p>\n