[KUDU-1807] GetTableSchema() is O(n) in the number of tablets

• Type: Sub-task
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.6.0
• Component/s: master, perf
• Labels: data-scalability
• Target Version/s: 1.6.0
• Code Review: https://gerrit.cloudera.org/#/c/8027
• Assignee: Adar Dembo
• Reporter: Todd Lipcon
• Created: 13/Dec/16 06:12
• Updated: 18/Sep/17 23:47
• Resolved: 18/Sep/17 23:47

Description

GetTableSchema calls TableInfo::IsCreateTableDone. This method checks each tablet for whether it is in the correct state, which requires acquiring the RWC lock for every tablet. This is somewhat slow for large tables with thousands of tablets, and this is actually a relatively hot path because every task in an Impala query ends up calling GetTableSchema() when it opens its scanner.