ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> [V2] PQsendQuery (V2; original)
> [V3] PQsendQueryParams (V3)
> [V3P] PQsendQueryPrepared (V3 with prepared statements)
> V3 was 12% slower than V2, and V3P was 40% faster than V2.
Those aren't really comparable, because the functionality is different.
Did you check plain PQSendQuery on both V2 and V3?
regards, tom lane