To answer your question about getting the first 10 rows, you can use the LIMIT clause, which will influence the planner's decisions. Or you can declare a cursor for your query and only fetch the first 10 rows.

As for GCC, it's usually up to the packagers, but the source tree after running ./configure gets compiled with:

  -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wformat-security -fno-strict-aliasing -fwrapv