pl/python quoting functions

diff --git a/doc/src/sgml/plpython.sgml b/doc/src/sgml/plpython.sgml
index e05c293..8a995b2 100644
*** a/doc/src/sgml/plpython.sgml
--- b/doc/src/sgml/plpython.sgml
*************** $$ LANGUAGE plpythonu;
*** 997,1002 ****
--- 997,1018 ----
     <xref linkend="guc-client-min-messages"> configuration
     variables. See <xref linkend="runtime-config"> for more information.
    </para>
+   <para>
+    Another set of utility functions
+    are <literal>plpy.quote_literal(<replaceable>string</>)</literal>,
+    <literal>plpy.quote_nullable(<replaceable>string</>)</literal>
+    and <literal>plpy.quote_ident(<replaceable>string</>)</literal>. They are
+    equivalent to the builtin quoting functions described
+    in <xref linkend="functions-string">. They are useful when constructing
+    ad-hoc queries. A PL/Python equivalent of dynamic SQL
+    from <xref linkend="plpgsql-quote-literal-example"> would be:
+ <programlisting>
+ plpy.execute("UPDATE tbl SET %s = %s where key = %s" % (
+     plpy.quote_ident(colname),
+     plpy.quote_nullable(newvalue),
+     plpy.quote_literal(keyvalue)))
+ </programlisting>
+   </para>
   </sect1>
  
   <sect1 id="plpython-envar">
diff --git a/src/pl/plpython/Makefile b/src/pl/plpython/Makefile
index 16d78ae..292e360 100644
*** a/src/pl/plpython/Makefile
--- b/src/pl/plpython/Makefile
*************** REGRESS = \
*** 79,84 ****
--- 79,85 ----
  	plpython_types \
  	plpython_error \
  	plpython_unicode \
+ 	plpython_quote \
  	plpython_drop
  # where to find psql for running the tests
  PSQLDIR = $(bindir)
diff --git a/src/pl/plpython/expected/plpython_quote.out b/src/pl/plpython/expected/plpython_quote.out
index ...b33ee3f .
*** a/src/pl/plpython/expected/plpython_quote.out
--- b/src/pl/plpython/expected/plpython_quote.out
***************
*** 0 ****
--- 1,87 ----
+ -- test quoting functions
+ CREATE FUNCTION quote(t text, how text) RETURNS text AS $$
+     if how == "literal":
+         return plpy.quote_literal(t)
+     elif how == "nullable":
+         return plpy.quote_nullable(t)
+     elif how == "ident":
+         return plpy.quote_ident(t)
+     else:
+         raise plpy.Error("unrecognized quote type %s" % how)
+ $$ LANGUAGE plpythonu;
+ SELECT quote(t, 'literal') FROM (VALUES
+        ('abc'),
+        ('a''bc'),
+        ('''abc'''),
+        (''),
+        (''''),
+        ('xyzv')) AS v(t);
+    quote   
+ -----------
+  'abc'
+  'a''bc'
+  '''abc'''
+  ''
+  ''''
+  'xyzv'
+ (6 rows)
+ 
+ SELECT quote(t, 'nullable') FROM (VALUES
+        ('abc'),
+        ('a''bc'),
+        ('''abc'''),
+        (''),
+        (''''),
+        (NULL)) AS v(t);
+    quote   
+ -----------
+  'abc'
+  'a''bc'
+  '''abc'''
+  ''
+  ''''
+  NULL
+ (6 rows)
+ 
+ SELECT quote(t, 'ident') FROM (VALUES
+        ('abc'),
+        ('a b c'),
+        ('a " ''abc''')) AS v(t);
+     quote     
+ --------------
+  abc
+  "a b c"
+  "a "" 'abc'"
+ (3 rows)
+ 
+ -- test errors
+ SELECT quote(NULL::text, 'literal');
+ ERROR:  TypeError: argument 1 must be string, not None
+ CONTEXT:  PL/Python function "quote"
+ SELECT quote(NULL::text, 'ident');
+ ERROR:  TypeError: argument 1 must be string, not None
+ CONTEXT:  PL/Python function "quote"
+ SELECT quote('abc', 'random');
+ ERROR:  plpy.Error: unrecognized quote type random
+ CONTEXT:  PL/Python function "quote"
+ DO $$ plpy.quote_literal(3) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: argument 1 must be string, not int
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_literal(None) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: argument 1 must be string, not None
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_literal({'a': 'b'}) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: argument 1 must be string, not dict
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_literal() $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: function takes exactly 1 argument (0 given)
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_literal(1, 2) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: function takes exactly 1 argument (2 given)
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_nullable([1, 2]) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: argument 1 must be string or None, not list
+ CONTEXT:  PL/Python anonymous code block
+ DO $$ plpy.quote_ident(1.5) $$ LANGUAGE plpythonu;
+ ERROR:  TypeError: argument 1 must be string, not float
+ CONTEXT:  PL/Python anonymous code block
diff --git a/src/pl/plpython/expected/plpython_test.out b/src/pl/plpython/expected/plpython_test.out
index d92c987..961f6c0 100644
*** a/src/pl/plpython/expected/plpython_test.out
--- b/src/pl/plpython/expected/plpython_test.out
*************** contents.sort()
*** 43,51 ****
  return ", ".join(contents)
  $$ LANGUAGE plpythonu;
  select module_contents();
!                                       module_contents                                      
! -------------------------------------------------------------------------------------------
!  Error, Fatal, SPIError, debug, error, execute, fatal, info, log, notice, prepare, warning
  (1 row)
  
  CREATE FUNCTION elog_test() RETURNS void
--- 43,51 ----
  return ", ".join(contents)
  $$ LANGUAGE plpythonu;
  select module_contents();
!                                                             module_contents                                                            
! ---------------------------------------------------------------------------------------------------------------------------------------
!  Error, Fatal, SPIError, debug, error, execute, fatal, info, log, notice, prepare, quote_ident, quote_literal, quote_nullable, warning
  (1 row)
  
  CREATE FUNCTION elog_test() RETURNS void
diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index fff7de7..39c7e53 100644
*** a/src/pl/plpython/plpython.c
--- b/src/pl/plpython/plpython.c
*************** static PyObject *PLy_spi_execute_query(c
*** 2558,2563 ****
--- 2558,2567 ----
  static PyObject *PLy_spi_execute_plan(PyObject *, PyObject *, long);
  static PyObject *PLy_spi_execute_fetch_result(SPITupleTable *, int, int);
  
+ static PyObject *PLy_quote_literal(PyObject *, PyObject *);
+ static PyObject *PLy_quote_nullable(PyObject *, PyObject *);
+ static PyObject *PLy_quote_ident(PyObject *, PyObject *);
+ 
  
  static PyMethodDef PLy_plan_methods[] = {
  	{"status", PLy_plan_status, METH_VARARGS, NULL},
*************** static PyMethodDef PLy_methods[] = {
*** 2672,2677 ****
--- 2676,2688 ----
  	 */
  	{"execute", PLy_spi_execute, METH_VARARGS, NULL},
  
+ 	/*
+ 	 * escaping strings
+ 	 */
+ 	{"quote_literal", PLy_quote_literal, METH_VARARGS, NULL},
+ 	{"quote_nullable", PLy_quote_nullable, METH_VARARGS, NULL},
+ 	{"quote_ident", PLy_quote_ident, METH_VARARGS, NULL},
+ 
  	{NULL, NULL, 0, NULL}
  };
  
*************** PLy_output(volatile int level, PyObject
*** 3608,3613 ****
--- 3619,3683 ----
  	return Py_None;
  }
  
+ static PyObject *
+ PLy_quote_literal(PyObject *self, PyObject *args)
+ {
+ 	char		*str;
+ 	char		*quoted;
+ 	PyObject	*ret;
+ 
+ 	if (!PyArg_ParseTuple(args, "s", &str))
+ 		return NULL;
+ 
+ 	quoted = quote_literal_cstr(str);
+ 	ret = PyString_FromString(quoted);
+ 	pfree(quoted);
+ 
+ 	return ret;
+ }
+ 
+ static PyObject *
+ PLy_quote_nullable(PyObject *self, PyObject *args)
+ {
+ 	char		*str;
+ 	char		*quoted;
+ 	PyObject	*ret;
+ 
+ 	if (!PyArg_ParseTuple(args, "z", &str))
+ 		return NULL;
+ 
+ 	if (str == NULL)
+ 		return PyString_FromString("NULL");
+ 
+ 	quoted = quote_literal_cstr(str);
+ 	ret = PyString_FromString(quoted);
+ 	pfree(quoted);
+ 
+ 	return ret;
+ }
+ 
+ static PyObject *
+ PLy_quote_ident(PyObject *self, PyObject *args)
+ {
+ 	char		*str;
+ 	char		*quoted;
+ 	PyObject	*ret;
+ 
+ 	if (!PyArg_ParseTuple(args, "s", &str))
+ 		return NULL;
+ 
+ 	/* cast to char * to avoid a "discards qualifier" warning */
+ 	quoted = (char *) quote_identifier(str);
+ 	ret = PyString_FromString(quoted);
+ 	/*
+ 	 * quote_identifier sometimes returns a palloc'd string, and sometimes
+ 	 * just the pointer passed
+ 	 */
+ 	if (quoted != str)
+ 		pfree(quoted);
+ 
+ 	return ret;
+ }
  
  /*
   * Get the name of the last procedure called by the backend (the
diff --git a/src/pl/plpython/sql/plpython_quote.sql b/src/pl/plpython/sql/plpython_quote.sql
index ...15cab3c .
*** a/src/pl/plpython/sql/plpython_quote.sql
--- b/src/pl/plpython/sql/plpython_quote.sql
***************
*** 0 ****
--- 1,45 ----
+ -- test quoting functions
+ 
+ CREATE FUNCTION quote(t text, how text) RETURNS text AS $$
+     if how == "literal":
+         return plpy.quote_literal(t)
+     elif how == "nullable":
+         return plpy.quote_nullable(t)
+     elif how == "ident":
+         return plpy.quote_ident(t)
+     else:
+         raise plpy.Error("unrecognized quote type %s" % how)
+ $$ LANGUAGE plpythonu;
+ 
+ SELECT quote(t, 'literal') FROM (VALUES
+        ('abc'),
+        ('a''bc'),
+        ('''abc'''),
+        (''),
+        (''''),
+        ('xyzv')) AS v(t);
+ 
+ SELECT quote(t, 'nullable') FROM (VALUES
+        ('abc'),
+        ('a''bc'),
+        ('''abc'''),
+        (''),
+        (''''),
+        (NULL)) AS v(t);
+ 
+ SELECT quote(t, 'ident') FROM (VALUES
+        ('abc'),
+        ('a b c'),
+        ('a " ''abc''')) AS v(t);
+ 
+ -- test errors
+ SELECT quote(NULL::text, 'literal');
+ SELECT quote(NULL::text, 'ident');
+ SELECT quote('abc', 'random');
+ DO $$ plpy.quote_literal(3) $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_literal(None) $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_literal({'a': 'b'}) $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_literal() $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_literal(1, 2) $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_nullable([1, 2]) $$ LANGUAGE plpythonu;
+ DO $$ plpy.quote_ident(1.5) $$ LANGUAGE plpythonu;