Merge remote-tracking branch 'upstream/master'
ParsedUnionStmt
Union Assembler
Union - work in progress
ee side union plan node update
Fixed multiple unions in one statement. Added unit tests
UNION/UNION ALL set operations
Code review comments. EXCEPT/INTERSECT operations
Disallow T Union T
Partition check enhancement
Added Plan Processor
Allow UNIONs with multiple set operations
UnionSubPlanAssembler
Min cost bug fix
Code clean-up
Code review comments implementation
Merge branch 'master' into ENG-3091
ENG-3091 String expression indexes -- passes function tests.
Merge branch 'master' into ENG-3091
Add assert and safety comments.