Index: src/backend/tcop/postgres.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/tcop/postgres.c,v
retrieving revision 1.483
diff -c -r1.483 postgres.c
*** src/backend/tcop/postgres.c	4 Apr 2006 19:35:35 -0000	1.483
--- src/backend/tcop/postgres.c	15 Apr 2006 07:39:49 -0000
***************
*** 1870,1875 ****
--- 1870,1876 ----
  static void
  exec_describe_statement_message(const char *stmt_name)
  {
+ 	MemoryContext	oldContext;
  	PreparedStatement *pstmt;
  	TupleDesc	tupdesc;
  	ListCell   *l;
***************
*** 1882,1888 ****
  	start_xact_command();
  
  	/* Switch back to message context */
! 	MemoryContextSwitchTo(MessageContext);
  
  	/* Find prepared statement */
  	if (stmt_name[0] != '\0')
--- 1883,1889 ----
  	start_xact_command();
  
  	/* Switch back to message context */
! 	oldContext = MemoryContextSwitchTo(MessageContext);
  
  	/* Find prepared statement */
  	if (stmt_name[0] != '\0')
***************
*** 1940,1946 ****
--- 1941,1950 ----
  								  NULL);
  	else
  		pq_putemptymessage('n');	/* NoData */
+ 	
+ 	MemoryContextSwitchTo(oldContext);
  
+ 	finish_xact_command();
  }
  
  /*
***************
*** 1951,1956 ****
--- 1955,1961 ----
  static void
  exec_describe_portal_message(const char *portal_name)
  {
+ 	MemoryContext	oldContext;
  	Portal		portal;
  
  	/*
***************
*** 1960,1966 ****
  	start_xact_command();
  
  	/* Switch back to message context */
! 	MemoryContextSwitchTo(MessageContext);
  
  	portal = GetPortalByName(portal_name);
  	if (!PortalIsValid(portal))
--- 1965,1971 ----
  	start_xact_command();
  
  	/* Switch back to message context */
! 	oldContext = MemoryContextSwitchTo(MessageContext);
  
  	portal = GetPortalByName(portal_name);
  	if (!PortalIsValid(portal))
***************
*** 1992,1997 ****
--- 1997,2006 ----
  								  portal->formats);
  	else
  		pq_putemptymessage('n');	/* NoData */
+ 	
+ 	MemoryContextSwitchTo(oldContext);
+ 
+ 	finish_xact_command();
  }
  
  
Index: src/interfaces/libpq/fe-exec.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v
retrieving revision 1.182
diff -c -r1.182 fe-exec.c
*** src/interfaces/libpq/fe-exec.c	14 Mar 2006 22:48:23 -0000	1.182
--- src/interfaces/libpq/fe-exec.c	15 Apr 2006 07:39:58 -0000
***************
*** 55,60 ****
--- 55,62 ----
  static void parseInput(PGconn *conn);
  static bool PQexecStart(PGconn *conn);
  static PGresult *PQexecFinish(PGconn *conn);
+ static int pqDescribe(PGconn *conn, const char desc_type,
+ 					  const char *desc_target);
  
  
  /* ----------------
***************
*** 2281,2286 ****
--- 2283,2392 ----
  		return 0;
  }
  
+ 
+ /*
+  * pqDescribe - Describe given prepared statement or portal.
+  *
+  * Available options for target_type are
+  *   'S' to describe a prepared statement; or
+  *   'P' to describe a portal.
+  * Returns 0 on success and 1 on failure.
+  *
+  * By issuing a PQgetResult(), response from the server will be placed
+  * in an empty PGresult which will be extractable via PQf*() function family.
+  */
+ static int
+ pqDescribe(PGconn *conn, const char desc_type, const char *desc_target)
+ {
+ 	int	ret;
+ 
+ 	/* This isn't gonna work on a 2.0 server. */
+ 	if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
+ 	{
+ 		printfPQExpBuffer(&conn->errorMessage,
+ 						  libpq_gettext("function requires at least protocol version 3.0\n"));
+ 		return 1;
+ 	}
+ 	
+ 	if (!conn)
+ 		return 1;
+ 	
+ 	/* Clear the connection error message. */
+ 	resetPQExpBuffer(&conn->errorMessage);
+ 
+ 	/* Don't try to send if we know there's no live connection. */
+ 	if (conn->status != CONNECTION_OK)
+ 	{
+ 		printfPQExpBuffer(&conn->errorMessage,
+ 						  libpq_gettext("no connection to the server\n"));
+ 		return 1;
+ 	}
+ 	
+ 	/* Can't send while already busy, either. */
+ 	if (conn->asyncStatus != PGASYNC_IDLE)
+ 	{
+ 		printfPQExpBuffer(&conn->errorMessage,
+ 						  libpq_gettext("another command is already in progress\n"));
+ 		return 1;
+ 	}
+ 
+ 	/* Initialize async result-accumulation state. */
+ 	conn->result = NULL;
+ 	conn->curTuple = NULL;
+ 	
+ 	if (desc_target)
+ 		ret = (pqPutMsgStart('D', false, conn) < 0 ||
+ 			   pqPutc(desc_type, conn) < 0 ||
+ 			   pqPuts(desc_target, conn) < 0 ||
+ 			   pqPutMsgEnd(conn) < 0);
+ 	
+ 	/* NULL desc_target values will be treated as an empty string. */
+ 	else
+ 		ret = (pqPutMsgStart('D', false, conn) < 0 ||
+ 			   pqPutc(desc_type, conn) < 0 ||
+ 			   pqPutc('\0', conn) < 0 ||
+ 			   pqPutMsgEnd(conn) < 0);
+ 	
+ 	if (ret)
+ 		goto SendFailure;
+ 	
+ 	/* Extended protocol requires a Sync message. */
+ 	if (pqPutMsgStart('S', false, conn) < 0 ||
+ 		pqPutMsgEnd(conn) < 0)
+ 		goto SendFailure;
+ 
+ 	/* Remember we are using extended query protocol. */
+ 	conn->queryclass = PGQUERY_EXTENDED;
+ 
+ 	/* Free last query string. */
+ 	if (conn->last_query)
+ 	{
+ 		free(conn->last_query);
+ 		conn->last_query = NULL;
+ 	}
+ 
+ 	/* Describe request is sent. */
+ 	conn->asyncStatus = PGASYNC_BUSY;
+ 	return 0;
+ 
+ SendFailure:
+ 	pqHandleSendFailure(conn);
+ 	return 1;
+ }
+ 
+ int
+ PQdescribePrepared(PGconn *conn, const char *stmt)
+ {
+ 	return pqDescribe(conn, 'S', stmt);
+ }
+ 
+ int
+ PQdescribePortal(PGconn *conn, const char *portal)
+ {
+ 	return pqDescribe(conn, 'P', portal);
+ }
+ 
+ 
  /* PQsetnonblocking:
   *	sets the PGconn's database connection non-blocking if the arg is TRUE
   *	or makes it non-blocking if the arg is FALSE, this will not protect
***************
*** 2346,2351 ****
--- 2452,2458 ----
  	free(ptr);
  }
  
+ 
  /*
   * PQfreeNotify - free's the memory associated with a PGnotify
   *
Index: src/interfaces/libpq/fe-protocol3.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/fe-protocol3.c,v
retrieving revision 1.26
diff -c -r1.26 fe-protocol3.c
*** src/interfaces/libpq/fe-protocol3.c	14 Mar 2006 22:48:23 -0000	1.26
--- src/interfaces/libpq/fe-protocol3.c	15 Apr 2006 07:40:05 -0000
***************
*** 42,50 ****
--- 42,56 ----
  	((id) == 'T' || (id) == 'D' || (id) == 'd' || (id) == 'V' || \
  	 (id) == 'E' || (id) == 'N' || (id) == 'A')
  
+ /*
+  * Flag to distinguish between an odd RowDescription and start of
+  * a tuple returning query.
+  */
+ static bool parsing_row_desc = false;
  
  static void handleSyncLoss(PGconn *conn, char id, int msgLength);
  static int	getRowDescriptions(PGconn *conn);
+ static int	getParamDescriptions(PGconn *conn);
  static int	getAnotherTuple(PGconn *conn, int msgLength);
  static int	getParameterStatus(PGconn *conn);
  static int	getNotify(PGconn *conn);
***************
*** 206,221 ****
--- 212,247 ----
  					}
  					strncpy(conn->result->cmdStatus, conn->workBuffer.data,
  							CMDSTATUS_LEN);
+ 
+ 					/* This cannot be a Describe ('D') response no more. */
+ 					parsing_row_desc = false;
+ 					
  					conn->asyncStatus = PGASYNC_READY;
  					break;
  				case 'E':		/* error return */
  					if (pqGetErrorNotice3(conn, true))
  						return;
  					conn->asyncStatus = PGASYNC_READY;
+ 
+ 					/* No further RowDescription parsing is possible. */
+ 					parsing_row_desc = false;
  					break;
  				case 'Z':		/* backend is ready for new query */
  					if (getReadyForQuery(conn))
  						return;
+ 					
+ 					if (parsing_row_desc)
+ 					{
+ 						/*
+ 						 * This is probably received from a Describe ('D')
+ 						 * query's response.
+ 						 */
+ 						parsing_row_desc = false;
+ 						conn->asyncStatus = PGASYNC_READY;
+ 						return;
+ 					}
+ 					
+ 					/* Backend is ready for a new query. */
  					conn->asyncStatus = PGASYNC_IDLE;
  					break;
  				case 'I':		/* empty query */
***************
*** 268,273 ****
--- 294,302 ----
  						/* First 'T' in a query sequence */
  						if (getRowDescriptions(conn))
  							return;
+ 						
+ 						/* Turning "RowDesc is parsed" flag to on. */
+ 						parsing_row_desc = true;
  					}
  					else
  					{
***************
*** 294,299 ****
--- 323,348 ----
  						conn->result = PQmakeEmptyPGresult(conn,
  														   PGRES_COMMAND_OK);
  					break;
+ 				case 't':		/* Parameter Description */
+ 					if (!conn->result)
+ 					{
+ 						/* A new PGresult will be created to load parsed data into. */
+ 						if (getParamDescriptions(conn))
+ 							return;
+ 						
+ 						/* Result is ready. */
+ 						conn->asyncStatus = PGASYNC_READY;
+ 					}
+ 					else
+ 					{
+ 						/*
+ 						 * We'll wait until the application accepts the current
+ 						 * existing result.
+ 						 */
+ 						conn->asyncStatus = PGASYNC_READY;
+ 						return;
+ 					}
+ 					break;
  				case 'D':		/* Data Row */
  					if (conn->result != NULL &&
  						conn->result->resultStatus == PGRES_TUPLES_OK)
***************
*** 500,505 ****
--- 549,620 ----
  }
  
  /*
+  * parseInput subroutine to read a 't' (ParameterDescription) message.
+  * Returns 0 if parsing is completed, 1 if there isn't enough data yet
+  * and EOF if an error occurs.
+  *
+  * Parsed data will get loaded into the existing conn->result.
+  */
+ static int
+ getParamDescriptions(PGconn *conn)
+ {
+ 	PGresult	*res;
+ 	int			 nattr;
+ 	int			 i;
+ 	Oid			 typid;
+ 	
+ 	res = PQmakeEmptyPGresult(conn, PGRES_COMMAND_OK);
+ 	if (!res)
+ 	{
+ 		printfPQExpBuffer(&conn->errorMessage,
+ 						  libpq_gettext("out of memory\n"));
+ 		EOF;
+ 	}
+ 
+ 	/* First extracting number of attributes from the message. */
+ 	if (pqGetInt(&nattr, 2, conn) < 0)
+ 		goto NotEnoughData;
+ 	res->numAttributes = nattr;
+ 
+ 	/* Allocate space for the attribute descriptors. */		
+ 	if (nattr > 0)
+ 	{
+ 		int sz = nattr * sizeof(PGresAttDesc);
+ 		
+ 		res->attDescs = (PGresAttDesc *) pqResultAlloc(res, sz, TRUE);
+ 		if (!res->attDescs)
+ 		{
+ 			printfPQExpBuffer(&conn->errorMessage,
+ 							  libpq_gettext("out of memory\n"));
+ 			goto Error;
+ 		}
+ 		
+ 		/* Reset attribute values. */
+ 		MemSet(res->attDescs, 0, sz);
+ 	}
+ 
+ 	/* Loop through attribute's type OIDs. */
+ 	for (i = 0; i < nattr; i++)
+ 	{
+ 		if (pqGetInt(&typid, 4, conn) < 0)
+ 			goto NotEnoughData;
+ 		res->attDescs[i].typid = typid;
+ 	}
+ 
+ 	/* Success. */
+ 	conn->result = res;
+ 	return 0;
+ 
+ NotEnoughData:
+ 	PQclear(res);
+ 	return 1;
+ 
+ Error:
+ 	PQclear(res);
+ 	return EOF;
+ }
+ 
+ /*
   * parseInput subroutine to read a 'D' (row data) message.
   * We add another tuple to the existing PGresult structure.
   * Returns: 0 if completed message, EOF if error or not enough data yet.
Index: src/interfaces/libpq/libpq-fe.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/interfaces/libpq/libpq-fe.h,v
retrieving revision 1.126
diff -c -r1.126 libpq-fe.h
*** src/interfaces/libpq/libpq-fe.h	20 Mar 2006 15:07:05 -0000	1.126
--- src/interfaces/libpq/libpq-fe.h	15 Apr 2006 07:40:08 -0000
***************
*** 414,419 ****
--- 414,423 ----
  extern int	PQgetlength(const PGresult *res, int tup_num, int field_num);
  extern int	PQgetisnull(const PGresult *res, int tup_num, int field_num);
  
+ /* Describe prepared statements and portals. */
+ extern int	PQdescribePrepared(PGconn *conn, const char *stmt);
+ extern int	PQdescribePortal(PGconn *conn, const char *portal);
+ 
  /* Delete a PGresult */
  extern void PQclear(PGresult *res);