[IMPALA-8405] Document UDA state machine

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Docs
• Labels: impala_user_docs_open
• Epic Color: ghx-label-7
• Assignee: Unassigned
• Reporter: Tim Armstrong
• Created: 10/Apr/19 20:08
• Updated: 16/Mar/20 17:18

Description

The documentation in "The Underlying Functions for a UDA" doesn't do a good job of explaining the state transitions that a UDA can go through. E.g. when is Serialize() called. It's complicated because data needs to be serialized to go over the network, but sometimes is serialized to spill to disk, which changes the sequence of function calls.

See https://community.cloudera.com/t5/Interactive-Short-cycle-SQL/Function-execution-flow-in-UDAs-and-memory-implications-for/m-p/88892#M5532?eid=1&aid=1 for a user who is trying to understand this.