feat(hogql): support UNION ALL #14593
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Twixes
reviewed
Mar 7, 2023
posthog/hogql/printer.py
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| @@ -137,6 +137,14 @@ def visit_select_query(self, node: ast.SelectQuery): | |||
| if node.limit_with_ties: | |||
| clauses.append("WITH TIES") | |||
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| if len(node.union_all or []) > 0: | |||
| # :TRICKY: union queries are not "children" the parent select, but "siblings". Adjust the stack for the visit | |||
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Perhaps UNION should be a level above SELECT? That's how ClickHouse does this (https://github.com/ClickHouse/ClickHouse/blob/6d48bb25ff2519b84306a7abb1c17ffe60034f20/src/Analyzer/UnionNode.h) – there's UnionNode (which represents either UNION, EXCEPT, or INTERSECT) with the constituent queries as children. Then on the query tree level, they treat SELECT ... and SELECT ... UNION SELECT ... as interchangeable constructs (https://github.com/ClickHouse/ClickHouse/blob/6d48bb25ff2519b84306a7abb1c17ffe60034f20/src/Analyzer/QueryTreeBuilder.cpp#LL142C33-L142C33).
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I guess that makes sense. I've updated the code to do just that. Ready for another look.
Twixes
approved these changes
Mar 10, 2023
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Changes
Support
UNION ALLsyntax.How did you test this code?
Added a few tests