Paul Rogers created IMPALA-8021: ----------------------------------- Summary: Add estimated cardinality to EXPLAIN output Key: IMPALA-8021 URL: https://issues.apache.org/jira/browse/IMPALA-8021 Project: IMPALA Issue Type: Improvement Components: Frontend Affects Versions: Impala 3.1.0 Reporter: Paul Rogers Assignee: Paul Rogers
The EXPLAIN output provides much useful information in the plan tree. But, it lacks a vital piece of information: the expected cardinality at each step. All our planning decisions are based on this cardinality; we need it to make sense of the generated plan. Add cardinality to each node so it appears something like this: {noformat} HASH JOIN [INNER JOIN, BROADCAST] | rows=1.23G | |--SCAN HDFS [db.table] | partitions=2/123 files=2 size=4.56MB rows=7.89M {noformat} Only the scan and join have interesting cardinality numbers: Exchange nodes always have the same as their child. Aggregation may also be useful. -- This message was sent by Atlassian JIRA (v7.6.3#76005)