pgsql: Assert index_attnos[0] == 1 in ri_FastPathFlushArray()

Assert index_attnos[0] == 1 in ri_FastPathFlushArray()

ri_FastPathFlushArray() handles single-column FKs only, so
index_attnos[0] is always 1.  Add an Assert to make this invariant
explicit, as a followup to 980c1a85d819.

Suggested-by: Junwang Zhao <zhjwpku@gmail.com> (offlist)
Discussion:
https://www.postgresql.org/message-id/CADfhSr-pCkbDxmiOVYSAGE5QGjsQ48KKH_W424SPk%2BpwzKZFaQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/155c03ee9d449589fa93aabcac41d643d03875b9

Modified Files
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src/backend/utils/adt/ri_triggers.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)