[IGNITE-16315] Calcite engine. Query start request contains a lot of data

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Labels: calcite calcite3-required
• Assignee: Aleksey Plekhanov
• Reporter: Aleksey Plekhanov
• Created: 17/Jan/22 16:38
• Updated: 22/Mar/22 15:11
• Resolved: 03/Feb/22 07:43

Description

For simple queries SQL engine most of the time spend in writing/reading query start requests, which contains a lot of data. Nested instances of ColocationGroup class contain assignments for each partition (List<List<UUID>>). Transferred size can be reduced if we compact assignments somehow. The target colocation group from fragment description contains redundant synthetic partitions, this also can be optimized.

Messages workflow is not optimal too. First, we send QueryStartRequest to the remote nodes, remotes reply with the QueryStartResponse messages. After that remotes send batches with data to the target nodes and receive acks for each batch (acks required to limit inbox workload). When query execution is finished, the node initiator sends QueryCloseMessage to the remote nodes, remotes close queries, and sends back ErrorMessage to the initiator with the ExecutionCancelledException error (which is ignored on the initiator node).  

Also, some other optimizations are possible. Proposed changes:

• Implement compaction of assignments of ColocationGroup
• Reduce target colocation group partitions count
• Fix caching of query plans (store original SQL as key, not parsed SQL, to avoid redundant parsing)
• Change messages workflow (don't send ack messages for the last batch since it is redundant, self-close remote queries, and don't send close query messages to remote nodes, if we know for sure that it's already self-closed, don't send query start response if we already have sent batch for the same fragment before)
• Reduce count of RexBuilder creation on the execution phase (RexBuilder is stateless and can be used one static instance)
• Reduce count of Calcite types creation on the execution phase

Issue Links

• blocks: IGNITE-15436 Calcite engine. Merge Calcite SQL Engine to Ignite 2.x
• is duplicated by: IGNITE-12586 Calcite integration. NodesMapping simplification.
• is part of: IGNITE-12248 Apache Calcite based query execution engine
• links to: GitHub Pull Request #9751