pgsql: postgres_fdw: Add Assert to estimate_path_cost_size().

postgres_fdw: Add Assert to estimate_path_cost_size().

When estimating the cost/size of a pre-sorted path for a given upper
relation using local stats, this function dereferences the passed-in
PgFdwPathExtraData pointer without checking that it is not NULL. But
that is not a bug as the pointer is guaranteed to be non-NULL in that
case; to avoid confusion, add an Assert to ensure that it is not NULL
before dereferencing it.

Reported-by: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>
Author: Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com>
Reviewed-by: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAEudQArgiALbV1akQpeZOgim7XP05n%3DbDP1%3DTcOYLA43nRX_vA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/21c9756db6458f859e6579a6754c78154321cb39

Modified Files
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contrib/postgres_fdw/postgres_fdw.c | 7 +++++++
1 file changed, 7 insertions(+)