You can use Apache Hive explain logging to check that a materialized view used a
query rewrite.
By default explain logging is set to false in CDP.
-
In Cloudera Manager, enable explain logging: Navigate to , search for
hive.log.explain.output, check
HiveServer2 Default Group, and click Save Changes.
-
Verify that the query rewrite used the materialized view by running an extended
EXPLAIN statement:
EXPLAIN EXTENDED SELECT empid, deptname
FROM emps
JOIN depts
ON (emps.deptno = depts.deptno)
WHERE hire_date >= '2017-01-01'
AND hire_date <= '2019-01-01';
The output shows the alias
default.mv1 for the
materialized view in the TableScan section of the plan.
OPTIMIZED SQL: SELECT `empid`, `deptname`
FROM `default`.`mv1`
WHERE TIMESTAMP '2019-01-01 00:00:00.000000000' >= `hire_date`
STAGE DEPENDENCIES:
Stage-0 is a root stage
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: default.mv1
filterExpr: (hire_date <= TIMESTAMP'2019-01-01
00:00:00') (type: boolean) |
GatherStats: false
Filter Operator
isSamplingPred: false
predicate: (hire_date <= TIMESTAMP'2019-01-01
00:00:00') (type: boolean)
Select Operator
expressions: empid (type: int), deptname (type: varchar(256))
outputColumnNames: _col0, _col1
ListSink
