[ https://issues.apache.org/jira/browse/SPARK-17791?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Apache Spark reassigned SPARK-17791: ------------------------------------ Assignee: (was: Apache Spark) > Join reordering using star schema detection > ------------------------------------------- > > Key: SPARK-17791 > URL: https://issues.apache.org/jira/browse/SPARK-17791 > Project: Spark > Issue Type: Sub-task > Components: SQL > Affects Versions: 2.1.0 > Reporter: Ioana Delaney > Priority: Critical > Attachments: StarJoinReordering1005.doc > > > This JIRA is a sub-task of SPARK-17626. > The objective is to provide a consistent performance improvement for star > schema queries. Star schema consists of one or more fact tables referencing a > number of dimension tables. In general, queries against star schema are > expected to run fast because of the established RI constraints among the > tables. This design proposes a join reordering based on natural, generally > accepted heuristics for star schema queries: > * Finds the star join with the largest fact table and places it on the > driving arm of the left-deep join. This plan avoids large tables on the > inner, and thus favors hash joins. > * Applies the most selective dimensions early in the plan to reduce the > amount of data flow. > The design description is included in the below attached document. > \\ -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org