There are some main responsibilities of index handler, they are:
– At the time of CREATE INDEX, it validates the format of the base table and also generates the structure of the index table (if any). Moreover, it fills any additional information into the index’s storage descriptor as well.
– Further, it produces a plan for reading the base table’s data and writing to the index storage and/or index table, at the time of REBUILD.
– Moreover, it deletes any index-specific storage, during DROP.
Note: index tables are dropped automatically by Hive
– Also, at the time of queries, index handler participates in optimization, to convert operators like filters into index access plans.