pgsql: Remove useless lookup of root partitioned rel inExecInitModifyT

Remove useless lookup of root partitioned rel in ExecInitModifyTable().

node->partitioned_rels is only set in UPDATE/DELETE cases, but
ExecInitModifyTable only uses its "rel" variable in INSERT cases,
so the extra logic to find the root rel is just a waste of complexity
and cycles.

Etsuro Fujita, reviewed by Amit Langote

Discussion: https://postgr.es/m/93cf9816-2f7d-0f67-8ed2-4a4e497a6ab8@lab.ntt.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/dca48d145e0e757f0549430ec48687d12c6b6751

Modified Files
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src/backend/executor/nodeModifyTable.c | 19 +------------------
1 file changed, 1 insertion(+), 18 deletions(-)