Hadoop Hive - Hadoop Hive- Joins
join_table: table_reference JOIN table_factor [join_condition] | table_reference {LEFT|RIGHT|FULL} [OUTER] JOIN table_reference join_condition | table_reference LEFT SEMI JOIN table_reference join_condition table_reference: table_factor | join_table table_factor: tbl_name [alias] | table_subquery alias | ( table_references ) join_condition: ON equality_expression ( AND equality_expression )* equal
Join optimization in hive
This document discusses optimization techniques for map join in Hive. It describes: 1) Previous approaches to common join and map join in Hive and their limitations. 2) Optimized map join techniques like uploading small tables to distributed cache and performing local joins to avoid shuffle. 3) Using JDBM for hash tables caused performance issues so alternative approaches were evaluated. 4) Automa
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Join Strategies in Hive Liyin Tang, Namit Jain Software Engineer Facebook 1 Common Join 2 Map Join 3 Auto MapJoin 4 Bucket Map Join 5 Bucket Sort Merge Map Join 6 Skew Join Agenda Common Join Task A Mapper Mapper Table X Mapper … … Mapper Mapper… Ma
