[ https://issues.apache.org/jira/browse/IMPALA-1374?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Armstrong reassigned IMPALA-1374: ------------------------------------- Assignee: (was: Alexander Behm) > Improve Join Order Planning > --------------------------- > > Key: IMPALA-1374 > URL: https://issues.apache.org/jira/browse/IMPALA-1374 > Project: IMPALA > Issue Type: Bug > Components: Frontend > Affects Versions: Impala 1.3.2 > Reporter: Ryan Bosshart > Priority: Minor > Labels: performance, planner > Attachments: consolidatedqueries_fast, consolidatedqueries_slow > > > The join order is determined entirely by total size (#rows * column width). > This makes sense in general. However, when the fact table size (after > partition pruning) is close to the dim table, it can be a wrong choice > because the join key from the fact table is duplicated many many times. This > will make the hash chain very long. > On an almost identical query (similar join condition, tables, & number of > results), this caused a query time of ~10 seconds for one query and ~3 > minutes for the other (first row fetched, queries attached). -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org