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https://issues.apache.org/jira/browse/PHOENIX-671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14258135#comment-14258135
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James Taylor commented on PHOENIX-671:
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Adding support for UNION would be pretty straightforward. Here's what would be
required:
- Add support to PhoenixSQL.g for UNION. This would just be a select_statement
followed by one or more { UNION select_statement}.
- Modify QueryCompiler for the case of union to compile each individual
select_statement through the standard QueryCompile method.
- Produce a RowProjector that is the union of all projected expressions across
all select_statements.
- Produce a new UnionPlan which would pass in a List<QueryPlan> for the
compilation of all other statements.
- Implement the iterator() method of UnionPlan to just instantiate a
ConcatIterator which is the concatenation of all iterators from the
List<QueryPlan> child plans.
In this case, the output would just be the concatenation of running all the
select statements, one after the other, with a bit of intelligence in the
formation of the RowProjector (which defines the "schema" of the tuples
returned across all select statements).
> Support UNION
> -------------
>
> Key: PHOENIX-671
> URL: https://issues.apache.org/jira/browse/PHOENIX-671
> Project: Phoenix
> Issue Type: Task
> Reporter: James Taylor
>
> This is particularly useful for Pentaho support.
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