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Allow partitionwise join to handle nested FULL JOIN USING cases.

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This case didn't work because columns merged by FULL JOIN USING are
represented in the parse tree by COALESCE expressions, and the logic
for recognizing a partitionable join failed to match upper-level join
clauses to such expressions.  To fix, synthesize suitable COALESCE
expressions and add them to the nullable_partexprs lists.  This is
pretty ugly and brute-force, but it gets the job done.  (I have
ambitions of rethinking the way outer-join output Vars are
represented, so maybe that will provide a cleaner solution someday.
For now, do this.)

Amit Langote, reviewed by Justin Pryzby, Richard Guo, and myself

Discussion: https://postgr.es/m/CA+HiwqG2WVUGmLJqtR0tPFhniO=H=9qQ+Z3L_ZC+Y3-EVQHFGg@mail.gmail.com
This commit is contained in:
Tom Lane
2020-04-07 22:12:14 -04:00
parent c8434d64ce
commit 981643dcdb
4 changed files with 174 additions and 2 deletions
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3
src/include/nodes/pathnodes.h
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@ -615,6 +615,9 @@ typedef struct PartitionSchemeData *PartitionScheme;
* that expression goes in the partexprs[i] list if the base relation
* is not nullable by this join or any lower outer join, or in the
* nullable_partexprs[i] list if the base relation is nullable.
* Furthermore, FULL JOINs add extra nullable_partexprs expressions
* corresponding to COALESCE expressions of the left and right join columns,
* to simplify matching join clauses to those lists.
*----------
*/
typedef enum RelOptKind