pgsql: postgres_fdw: Remove redundancy inpostgresAcquireSampleRowsFunc

postgres_fdw: Remove redundancy in postgresAcquireSampleRowsFunc().

Previously, in the loop in postgresAcquireSampleRowsFunc() to iterate
fetching rows from a given remote table, we redundantly 1) determined the
fetch size by parsing the table's server/table-level options and then 2)
constructed the fetch command; remove that redundancy.

Author: Etsuro Fujita
Reviewed-by: Julien Rouhaud
Discussion: https://postgr.es/m/CAPmGK17_urk9qkLV65_iYMFw64z5qhdfhY=tMVV6Jg4KNYx8+w@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2a1612104cadbfdc739ff0370f279779f323c3b5

Modified Files
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contrib/postgres_fdw/postgres_fdw.c | 63 ++++++++++++++++++++-----------------
1 file changed, 34 insertions(+), 29 deletions(-)