Add CTE support #47
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Add CTE support #47
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thoshiai
reviewed
Jan 20, 2023
Simple CTEs which does not contain aggregates or DISTINCT are now supported similarly to simple sub-queries. Before a view is maintained, all CTEs are converted to corresponding subqueries to enable to treat CTEs as same as subqueries. For this end, codes of the static fnction inline_cte in the core (optimizer/plan/subselect.c) was imported.
When a table in a unreferenced CTE is TRUNCATEd, the contents of the IMMV is not affected so it must not be truncated. For confirming it at the maintenance time, we have to check if the modified table used in a CTE is actually referenced. Although it would possible, we just disallow to create such IMMVs for now since such unreferenced CTE is useless unless it doesn't contain modifying commands, that is already prohibited. Some error messages are fixed to use "WITH query" instead of "CTE" as same as in the PostgreSQL core code. Also, add tests for nested CTE and multiply-referenced CTE, and a test for nested-subquery in passing.
thoshiai
approved these changes
Jan 29, 2023
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Simple CTEs which does not contain aggregates or DISTINCT are now supported similarly to simple sub-queries.
Before a view is maintained, all CTEs are converted to corresponding subqueries to enable to treat CTEs as same as subqueries. For this end, codes of the static fnction inline_cte in the core (optimizer/plan/subselect.c) was imported.