FoundationDB/sql-layer — pull request #1000 by tjoneslo (2013-10-23 02:08:32+00:00)
Title: Add union support

Update the query processor to support UNION [ALL] and correctly process the results.

Key changes are
- Refactor the two Union operators into a single UnionBase to capture and simplify the operators
- Add two new errors for incorrectly written unions.
- The ASTStatementLoader to process the UnionNode -> Union process is brute force to manage to ensure the two streams of data into the Union operator have all the same (exact) types, and the output does too.
- The OperatorAssembler doing the Union -> Union Operator also inserts sorts for the UNION processing

Plus many new tests to verify the union works.