Creating an Index -- 创建一个索引

CREATE TABLE employees (
  name         STRING,
  salary       FLOAT,
  subordinates ARRAY,
  deductions   MAP,
  address      STRUCT
)
PARTITIONED BY (country STRING, state STRING);

Let’s index on the country partition only:

CREATE INDEX employees_index
ON TABLE employees (country)
AS 'org.apache.hadoop.hive.ql.index.compact.CompactIndexHandler'
WITH DEFERRED REBUILD
IDXPROPERTIES ('creator = 'me', 'created_at' = 'some_time')
IN TABLE employees_index_table
PARTITIONED BY (country, name)
COMMENT 'Employees indexed by country and name.';

Bitmap Indexes

Hive v0.8.0 adds a built-in bitmap index handler. Bitmap indexes are commonly used
for columns with few distinct values. Here is our previous example rewritten to use the
bitmap index handler:

CREATE INDEX employees_index
ON TABLE employees (country)
AS 'BITMAP'
WITH DEFERRED REBUILD
IDXPROPERTIES ('creator = 'me', 'created_at' = 'some_time')
IN TABLE employees_index_table
PARTITIONED BY (country, name)
COMMENT 'Employees indexed by country and name.';

Rebuilding the Index

ALTER INDEX employees_index
ON TABLE employees
PARTITION (country = 'US')
REBUILD;

Showing an Index

SHOW FORMATTED INDEX ON employees;

Dropping an Index

DROP INDEX IF EXISTS employees_index ON TABLE employees;