George Caragea created HAWQ-97:
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Summary: Improve performance of Metadata Versioning by eliminating
redundant versioning events
Key: HAWQ-97
URL: https://issues.apache.org/jira/browse/HAWQ-97
Project: Apache HAWQ
Issue Type: Improvement
Components: Metadata Versioning
Reporter: George Caragea
Assignee: George Caragea
A DDL command usually generates more than one Nuke Versioning event during its
execution. All these nuke events are then pushed to Shared Versioning Queue
(SVQ) at commit, and then all of them get propagated to other backends.
This is extra work and it can be optimized. We should push only one Nuke VE
instead of several.
Also, when moving messages from the Current Command Invalidation Queue (CVQ) to
the Prior Command Invalidation Queue (XVQ), pre-process the event queue to
eliminate any events that will have no effect. If a versioning event is
followed by a nuke event, it will have no effect.
Moreover, when a nuke event is moved to XVQ, everything prior in XVQ will
also have no effect.
Solution is to look for Nuke events in CVQ. Find the last one (in the order of
creation), then move all messages from then on to XVQ, overwriting XVQ.
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