Namit Jain created HIVE-3922: -------------------------------- Summary: repeated columns in join keys and join values Key: HIVE-3922 URL: https://issues.apache.org/jira/browse/HIVE-3922 Project: Hive Issue Type: Improvement Components: Query Processor Reporter: Namit Jain
A simple query like: > explain select a.*, b.* from src a join src b on a.key = b.key; OK ABSTRACT SYNTAX TREE: (TOK_QUERY (TOK_FROM (TOK_JOIN (TOK_TABREF (TOK_TABNAME src) a) (TOK_TABREF (TOK_TABNAME src) b) (= (. (TOK_TABLE_OR_COL a) key) (. (TOK_TABLE_OR_COL b) key)))) (TOK_INSERT (TOK_DESTINATION (TOK_DIR TOK_TMP_FILE)) (TOK_SELECT (TOK_SELEXPR (TOK_ALLCOLREF (TOK_TABNAME a))) (TOK_SELEXPR (TOK_ALLCOLREF (TOK_TABNAME b)))))) STAGE DEPENDENCIES: Stage-1 is a root stage Stage-0 is a root stage STAGE PLANS: Stage: Stage-1 Map Reduce Alias -> Map Operator Tree: a TableScan alias: a Reduce Output Operator key expressions: expr: key type: string sort order: + Map-reduce partition columns: expr: key type: string tag: 0 value expressions: expr: key type: string expr: value type: string b TableScan alias: b Reduce Output Operator key expressions: expr: key type: string sort order: + Map-reduce partition columns: expr: key type: string tag: 1 value expressions: expr: key type: string expr: value type: string shows that a.key and b.key are transferred twice across the map-reduce boundaries. This should be done away with. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira