explain postgres pecularity for param query out parameters

1 files changed, 21 insertions, 4 deletions

diff --git a/lib/odbc/test/postgres.erl b/lib/odbc/test/postgres.erl
index 811d5ebaed..0c1761b835 100644
--- a/lib/odbc/test/postgres.erl
+++ b/lib/odbc/test/postgres.erl
@@ -294,6 +294,7 @@ describe_dec_num() ->
 describe_timestamp() ->
     {ok, [{"field", sql_timestamp}]}.
 
+%-------------------------------------------------------------------------
 drop_proc() ->
     "drop function test_proc1(OUT integer, OUT integer);".
 
@@ -308,10 +309,26 @@ stored_proc_integer_out() ->
         "END " ++
         "$$ LANGUAGE plpgsql ".
 
+%% This does not test what you might think it is supposed to test.
+%% Since the stored procedure has got 2 out parameters and no
+%% in parameters it is of arity 0 as called below.
+%%
+%% The port program odbcserver.c will marshal these out parameters
+%% and hand them to ODBC. The ODBC driver for postgres will
+%% apparently not give a hoot about these out parameters and instead
+%% return the result in a regular result select set. The port program
+%% will assume it has the result in the out parameters and marshal
+%% these as they are i.e as it itself had packed them, so they
+%% come back unchanged.
+%%
+%% The real function result goes into the void but the code in odbcserver.c
+%% that marshals out parameters returned from ODBC will be run
+%% so that is what this test tests...
+%%
 param_query(Ref) ->
-    odbc:param_query(Ref, "select * from test_proc1(?, ?)",
-                     [{sql_integer, out, [123]},
-                      {sql_integer, out, [456]}]).
+    odbc:param_query(Ref, "select * from test_proc1()",
+                     [{sql_integer, out, [111]},
+                      {sql_integer, out, [444]}]).
 
 query_result() ->
-    {executed, 2, [{123, 456}]}.
+    {executed, 2, [{111, 444}]}.