Fix/improve bytea and boolean support in PL/Python

Before, PL/Python converted data between SQL and Python by going
through a C string representation.  This broke for bytea in two ways:

- On input (function parameters), you would get a Python string that
  contains bytea's particular external representation with backslashes
  etc., instead of a sequence of bytes, which is what you would expect
  in a Python environment.  This problem is exacerbated by the new
  bytea output format.

- On output (function return value), null bytes in the Python string
  would cause truncation before the data gets stored into a bytea
  datum.

This is now fixed by converting directly between the PostgreSQL datum
and the Python representation.

The required generalized infrastructure also allows for other
improvements in passing:

- When returning a boolean value, the SQL datum is now true if and
  only if Python considers the value that was passed out of the
  PL/Python function to be true.  Previously, this determination was
  left to the boolean data type input function.  So, now returning
  'foo' results in true, because Python considers it true, rather than
  false because PostgreSQL considers it false.

- On input, we can convert the integer and float types directly to
  their Python equivalents without having to go through an
  intermediate string representation.

original patch by Caleb Welton, with updates by myself

src/pl/plpython/sql/plpython_types.sql

@@ -16,6 +16,35 @@ SELECT * FROM test_type_conversion_bool(false);
 SELECT * FROM test_type_conversion_bool(null);
 
 
+-- test various other ways to express Booleans in Python
+CREATE FUNCTION test_type_conversion_bool_other(n int) RETURNS bool AS $$
+# numbers
+if n == 0:
+   ret = 0
+elif n == 1:
+   ret = 5
+# strings
+elif n == 2:
+   ret = ''
+elif n == 3:
+   ret = 'fa' # true in Python, false in PostgreSQL
+# containers
+elif n == 4:
+   ret = []
+elif n == 5:
+   ret = [0]
+plpy.info(ret, not not ret)
+return ret
+$$ LANGUAGE plpythonu;
+
+SELECT * FROM test_type_conversion_bool_other(0);
+SELECT * FROM test_type_conversion_bool_other(1);
+SELECT * FROM test_type_conversion_bool_other(2);
+SELECT * FROM test_type_conversion_bool_other(3);
+SELECT * FROM test_type_conversion_bool_other(4);
+SELECT * FROM test_type_conversion_bool_other(5);
+
+
 CREATE FUNCTION test_type_conversion_char(x char) RETURNS char AS $$
 plpy.info(x, type(x))
 return x
@@ -105,6 +134,7 @@ return x
 $$ LANGUAGE plpythonu;
 
 SELECT * FROM test_type_conversion_bytea('hello world');
+SELECT * FROM test_type_conversion_bytea(E'null\\000byte');
 SELECT * FROM test_type_conversion_bytea(null);
 
 
@@ -121,8 +151,6 @@ except ValueError, e:
     return 'FAILED: ' + str(e)
 $$ LANGUAGE plpythonu;
 
-/* This will currently fail because the bytea datum is presented to
-   Python as a string in bytea-encoding, which Python doesn't understand. */
 SELECT test_type_unmarshal(x) FROM test_type_marshal() x;
 
 
@@ -130,6 +158,17 @@ SELECT test_type_unmarshal(x) FROM test_type_marshal() x;
 -- Domains
 --
 
+CREATE DOMAIN booltrue AS bool CHECK (VALUE IS TRUE OR VALUE IS NULL);
+
+CREATE FUNCTION test_type_conversion_booltrue(x booltrue, y bool) RETURNS booltrue AS $$
+return y
+$$ LANGUAGE plpythonu;
+
+SELECT * FROM test_type_conversion_booltrue(true, true);
+SELECT * FROM test_type_conversion_booltrue(false, true);
+SELECT * FROM test_type_conversion_booltrue(true, false);
+
+
 CREATE DOMAIN uint2 AS int2 CHECK (VALUE >= 0);
 
 CREATE FUNCTION test_type_conversion_uint2(x uint2, y int) RETURNS uint2 AS $$
@@ -142,6 +181,17 @@ SELECT * FROM test_type_conversion_uint2(100::uint2, -50);
 SELECT * FROM test_type_conversion_uint2(null, 1);
 
 
+CREATE DOMAIN nnint AS int CHECK (VALUE IS NOT NULL);
+
+CREATE FUNCTION test_type_conversion_nnint(x nnint, y int) RETURNS nnint AS $$
+return y
+$$ LANGUAGE plpythonu;
+
+SELECT * FROM test_type_conversion_nnint(10, 20);
+SELECT * FROM test_type_conversion_nnint(null, 20);
+SELECT * FROM test_type_conversion_nnint(10, null);
+
+
 CREATE DOMAIN bytea10 AS bytea CHECK (octet_length(VALUE) = 10 AND VALUE IS NOT NULL);
 
 CREATE FUNCTION test_type_conversion_bytea10(x bytea10, y bytea) RETURNS bytea10 AS $$