Improve support for composite types in PL/Python.

Allow PL/Python functions to return arrays of composite types.
Also, fix the restriction that plpy.prepare/plpy.execute couldn't
handle query parameters or result columns of composite types.

In passing, adopt a saner arrangement for where to release the
tupledesc reference counts acquired via lookup_rowtype_tupdesc.
The callers of PLyObject_ToCompositeDatum were doing the lookups,
but then the releases happened somewhere down inside subroutines
of PLyObject_ToCompositeDatum, which is bizarre and bug-prone.
Instead release in the same function that acquires the refcount.

Ed Behn and Ronan Dunklau, reviewed by Abhijit Menon-Sen

doc/src/sgml/plpython.sgml

@@ -1026,13 +1026,6 @@ rv = plpy.execute(plan, ["name"], 5)
      <para>
       Query parameters and result row fields are converted between PostgreSQL
       and Python data types as described in <xref linkend="plpython-data">.
-      The exception is that composite types are currently not supported: They
-      will be rejected as query parameters and are converted to strings when
-      appearing in a query result.  As a workaround for the latter problem, the
-      query can sometimes be rewritten so that the composite type result
-      appears as a result row rather than as a field of the result row.
-      Alternatively, the resulting string could be parsed apart by hand, but
-      this approach is not recommended because it is not future-proof.
      </para>
 
      <para>

src/pl/plpython/expected/plpython_composite.out

@@ -257,7 +257,7 @@ SELECT * FROM changing_test();
  1 | (3,4)
 (2 rows)
 
--- tables of composite types (not yet implemented)
+-- tables of composite types
 CREATE FUNCTION composite_types_table(OUT tab table_record[], OUT typ type_record[] ) RETURNS SETOF record AS $$
 yield {'tab': [['first', 1], ['second', 2]],
       'typ': [{'first': 'third', 'second': 3},
@@ -270,9 +270,13 @@ yield {'tab': [['first', 1], ['second', 2]],
               {'first': 'fourth', 'second': 4}]}
 $$ LANGUAGE plpythonu;
 SELECT * FROM composite_types_table();
-ERROR:  PL/Python functions cannot return type table_record[]
-DETAIL:  PL/Python does not support conversion to arrays of row types.
-CONTEXT:  PL/Python function "composite_types_table"
+            tab             |            typ             
+----------------------------+----------------------------
+ {"(first,1)","(second,2)"} | {"(third,3)","(fourth,4)"}
+ {"(first,1)","(second,2)"} | {"(third,3)","(fourth,4)"}
+ {"(first,1)","(second,2)"} | {"(third,3)","(fourth,4)"}
+(3 rows)
+
 -- check what happens if the output record descriptor changes
 CREATE FUNCTION return_record(t text) RETURNS record AS $$
 return {'t': t, 'val': 10}

src/pl/plpython/expected/plpython_spi.out

@@ -376,6 +376,15 @@ plan = plpy.prepare("select fname, lname from users where fname like $1 || '%'",
                     ["text"])
 c = plpy.cursor(plan, ["a", "b"])
 $$ LANGUAGE plpythonu;
+CREATE TYPE test_composite_type AS (
+  a1 int,
+  a2 varchar
+);
+CREATE OR REPLACE FUNCTION plan_composite_args() RETURNS test_composite_type AS $$
+plan = plpy.prepare("select $1 as c1", ["test_composite_type"])
+res = plpy.execute(plan, [{"a1": 3, "a2": "label"}])
+return res[0]["c1"]
+$$ LANGUAGE plpythonu;
 SELECT simple_cursor_test();
  simple_cursor_test 
 --------------------
@@ -432,3 +441,9 @@ CONTEXT:  Traceback (most recent call last):
   PL/Python function "cursor_plan_wrong_args", line 4, in <module>
     c = plpy.cursor(plan, ["a", "b"])
 PL/Python function "cursor_plan_wrong_args"
+SELECT plan_composite_args();
+ plan_composite_args 
+---------------------
+ (3,label)
+(1 row)
+

src/pl/plpython/expected/plpython_types.out

@@ -630,15 +630,14 @@ ERROR:  invalid input syntax for integer: "abc"
 CONTEXT:  while creating return value
 PL/Python function "test_type_conversion_array_mixed2"
 CREATE FUNCTION test_type_conversion_array_record() RETURNS type_record[] AS $$
-return [None]
+return [{'first': 'one', 'second': 42}, {'first': 'two', 'second': 11}]
 $$ LANGUAGE plpythonu;
-ERROR:  PL/Python functions cannot return type type_record[]
-DETAIL:  PL/Python does not support conversion to arrays of row types.
 SELECT * FROM test_type_conversion_array_record();
-ERROR:  function test_type_conversion_array_record() does not exist
-LINE 1: SELECT * FROM test_type_conversion_array_record();
-                      ^
-HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
+ test_type_conversion_array_record 
+-----------------------------------
+ {"(one,42)","(two,11)"}
+(1 row)
+
 CREATE FUNCTION test_type_conversion_array_string() RETURNS text[] AS $$
 return 'abc'
 $$ LANGUAGE plpythonu;

src/pl/plpython/expected/plpython_types_3.out

@@ -630,15 +630,14 @@ ERROR:  invalid input syntax for integer: "abc"
 CONTEXT:  while creating return value
 PL/Python function "test_type_conversion_array_mixed2"
 CREATE FUNCTION test_type_conversion_array_record() RETURNS type_record[] AS $$
-return [None]
+return [{'first': 'one', 'second': 42}, {'first': 'two', 'second': 11}]
 $$ LANGUAGE plpython3u;
-ERROR:  PL/Python functions cannot return type type_record[]
-DETAIL:  PL/Python does not support conversion to arrays of row types.
 SELECT * FROM test_type_conversion_array_record();
-ERROR:  function test_type_conversion_array_record() does not exist
-LINE 1: SELECT * FROM test_type_conversion_array_record();
-                      ^
-HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
+ test_type_conversion_array_record 
+-----------------------------------
+ {"(one,42)","(two,11)"}
+(1 row)
+
 CREATE FUNCTION test_type_conversion_array_string() RETURNS text[] AS $$
 return 'abc'
 $$ LANGUAGE plpython3u;

src/pl/plpython/plpy_exec.c

@@ -194,6 +194,8 @@ PLy_exec_function(FunctionCallInfo fcinfo, PLyProcedure *proc)
 
 			rv = PLyObject_ToCompositeDatum(&proc->result, desc, plrv);
 			fcinfo->isnull = (rv == (Datum) NULL);
+
+			ReleaseTupleDesc(desc);
 		}
 		else
 		{

src/pl/plpython/plpy_spi.c

@@ -130,12 +130,7 @@ PLy_spi_prepare(PyObject *self, PyObject *args)
 
 			plan->types[i] = typeId;
 			typeStruct = (Form_pg_type) GETSTRUCT(typeTup);
-			if (typeStruct->typtype != TYPTYPE_COMPOSITE)
-				PLy_output_datum_func(&plan->args[i], typeTup);
-			else
-				ereport(ERROR,
-						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				   errmsg("plpy.prepare does not support composite types")));
+			PLy_output_datum_func(&plan->args[i], typeTup);
 			ReleaseSysCache(typeTup);
 		}
 

src/pl/plpython/plpy_typeio.c

@@ -404,11 +404,7 @@ PLy_output_datum_func2(PLyObToDatum *arg, HeapTuple typeTup)
 		Oid			funcid;
 
 		if (type_is_rowtype(element_type))
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("PL/Python functions cannot return type %s",
-							format_type_be(arg->typoid)),
-					 errdetail("PL/Python does not support conversion to arrays of row types.")));
+			arg->func = PLyObject_ToComposite;
 
 		arg->elm = PLy_malloc0(sizeof(*arg->elm));
 		arg->elm->func = arg->func;
@@ -742,6 +738,8 @@ PLyObject_ToComposite(PLyObToDatum *arg, int32 typmod, PyObject *plrv)
 	 */
 	rv = PLyObject_ToCompositeDatum(&info, desc, plrv);
 
+	ReleaseTupleDesc(desc);
+
 	PLy_typeinfo_dealloc(&info);
 
 	return rv;
@@ -835,11 +833,6 @@ PLySequence_ToArray(PLyObToDatum *arg, int32 typmod, PyObject *plrv)
 		else
 		{
 			nulls[i] = false;
-
-			/*
-			 * We don't support arrays of row types yet, so the first argument
-			 * can be NULL.
-			 */
 			elems[i] = arg->elm->func(arg->elm, -1, obj);
 		}
 		Py_XDECREF(obj);
@@ -872,7 +865,6 @@ PLyString_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *string)
 	PLy_output_datum_func2(&info->out.d, typeTup);
 
 	ReleaseSysCache(typeTup);
-	ReleaseTupleDesc(desc);
 
 	return PLyObject_ToDatum(&info->out.d, info->out.d.typmod, string);
 }
@@ -881,6 +873,7 @@ PLyString_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *string)
 static Datum
 PLyMapping_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *mapping)
 {
+	Datum		result;
 	HeapTuple	tuple;
 	Datum	   *values;
 	bool	   *nulls;
@@ -943,17 +936,20 @@ PLyMapping_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *mapping)
 	}
 
 	tuple = heap_form_tuple(desc, values, nulls);
-	ReleaseTupleDesc(desc);
+	result = heap_copy_tuple_as_datum(tuple, desc);
+	heap_freetuple(tuple);
+
 	pfree(values);
 	pfree(nulls);
 
-	return HeapTupleGetDatum(tuple);
+	return result;
 }
 
 
 static Datum
 PLySequence_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *sequence)
 {
+	Datum		result;
 	HeapTuple	tuple;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1029,17 +1025,20 @@ PLySequence_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *sequence)
 	}
 
 	tuple = heap_form_tuple(desc, values, nulls);
-	ReleaseTupleDesc(desc);
+	result = heap_copy_tuple_as_datum(tuple, desc);
+	heap_freetuple(tuple);
+
 	pfree(values);
 	pfree(nulls);
 
-	return HeapTupleGetDatum(tuple);
+	return result;
 }
 
 
 static Datum
 PLyGenericObject_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *object)
 {
+	Datum		result;
 	HeapTuple	tuple;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1101,11 +1100,13 @@ PLyGenericObject_ToComposite(PLyTypeInfo *info, TupleDesc desc, PyObject *object
 	}
 
 	tuple = heap_form_tuple(desc, values, nulls);
-	ReleaseTupleDesc(desc);
+	result = heap_copy_tuple_as_datum(tuple, desc);
+	heap_freetuple(tuple);
+
 	pfree(values);
 	pfree(nulls);
 
-	return HeapTupleGetDatum(tuple);
+	return result;
 }
 
 /*

src/pl/plpython/sql/plpython_composite.sql

@@ -125,7 +125,7 @@ SELECT * FROM changing_test();
 ALTER TABLE changing ADD COLUMN j integer;
 SELECT * FROM changing_test();
 
--- tables of composite types (not yet implemented)
+-- tables of composite types
 
 CREATE FUNCTION composite_types_table(OUT tab table_record[], OUT typ type_record[] ) RETURNS SETOF record AS $$
 yield {'tab': [['first', 1], ['second', 2]],

src/pl/plpython/sql/plpython_spi.sql

@@ -284,6 +284,17 @@ plan = plpy.prepare("select fname, lname from users where fname like $1 || '%'",
 c = plpy.cursor(plan, ["a", "b"])
 $$ LANGUAGE plpythonu;
 
+CREATE TYPE test_composite_type AS (
+  a1 int,
+  a2 varchar
+);
+
+CREATE OR REPLACE FUNCTION plan_composite_args() RETURNS test_composite_type AS $$
+plan = plpy.prepare("select $1 as c1", ["test_composite_type"])
+res = plpy.execute(plan, [{"a1": 3, "a2": "label"}])
+return res[0]["c1"]
+$$ LANGUAGE plpythonu;
+
 SELECT simple_cursor_test();
 SELECT double_cursor_close();
 SELECT cursor_fetch();
@@ -293,3 +304,4 @@ SELECT next_after_close();
 SELECT cursor_fetch_next_empty();
 SELECT cursor_plan();
 SELECT cursor_plan_wrong_args();
+SELECT plan_composite_args();

src/pl/plpython/sql/plpython_types.sql

@@ -269,7 +269,7 @@ SELECT * FROM test_type_conversion_array_mixed2();
 
 
 CREATE FUNCTION test_type_conversion_array_record() RETURNS type_record[] AS $$
-return [None]
+return [{'first': 'one', 'second': 42}, {'first': 'two', 'second': 11}]
 $$ LANGUAGE plpythonu;
 
 SELECT * FROM test_type_conversion_array_record();