Executable external table should be able to stop the external program in time after it get enough rows for the query.

[lij55]

Currently the 'executable external web table' need to run and wait the program finish even if there is a limit in query. for example,

test=# CREATE EXTERNAL web TABLE huge_data
(
    data text
)
EXECUTE E'for i in `seq 1 100000000`;do  echo "hello greenplum";done' ON MASTER
FORMAT 'CSV';
CREATE EXTERNAL TABLE
test=# select * from huge_data limit 3;

I tested in on GP6 but think both GP6 and GP7 are the same. this limitation will make any query on gp_toolkit.__gp_log_master_ext extremely slow if the pg_log directory is big.