When an ERROR happens on a dblink remote connection, take

pains to pass the ERROR message components locally, including
using the passed SQLSTATE. Also wrap the passed info in an
appropriate CONTEXT message. Addresses complaint by Henry
Combrinck. Joe Conway, with much good advice from Tom Lane.

contrib/dblink/dblink.c

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.73 2008/04/04 17:02:56 momjian Exp $
+ * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.74 2008/07/03 03:56:57 joe Exp $
  * Copyright (c) 2001-2008, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
@@ -94,6 +94,7 @@ static HeapTuple get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 p
 static Oid	get_relid_from_relname(text *relname_text);
 static char *generate_relation_name(Oid relid);
 static void dblink_security_check(PGconn *conn, remoteConn *rconn);
+static void dblink_res_error(const char *conname, PGresult *res, const char *dblink_context_msg, bool fail);
 
 /* Global */
 static remoteConn *pconn = NULL;
@@ -125,6 +126,14 @@ typedef struct remoteConnHashEnt
 		} \
 	} while (0)
 
+#define xpstrdup(var_c, var_) \
+	do { \
+		if (var_ != NULL) \
+			var_c = pstrdup(var_); \
+		else \
+			var_c = NULL; \
+	} while (0)
+
 #define DBLINK_RES_INTERNALERROR(p2) \
 	do { \
 			msg = pstrdup(PQerrorMessage(conn)); \
@@ -133,28 +142,6 @@ typedef struct remoteConnHashEnt
 			elog(ERROR, "%s: %s", p2, msg); \
 	} while (0)
 
-#define DBLINK_RES_ERROR(p2) \
-	do { \
-			msg = pstrdup(PQerrorMessage(conn)); \
-			if (res) \
-				PQclear(res); \
-			ereport(ERROR, \
-					(errcode(ERRCODE_SYNTAX_ERROR), \
-					 errmsg("%s", p2), \
-					 errdetail("%s", msg))); \
-	} while (0)
-
-#define DBLINK_RES_ERROR_AS_NOTICE(p2) \
-	do { \
-			msg = pstrdup(PQerrorMessage(conn)); \
-			if (res) \
-				PQclear(res); \
-			ereport(NOTICE, \
-					(errcode(ERRCODE_SYNTAX_ERROR), \
-					 errmsg("%s", p2), \
-					 errdetail("%s", msg))); \
-	} while (0)
-
 #define DBLINK_CONN_NOT_AVAIL \
 	do { \
 		if(conname) \
@@ -396,13 +383,8 @@ dblink_open(PG_FUNCTION_ARGS)
 	res = PQexec(conn, buf.data);
 	if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
 	{
-		if (fail)
+		dblink_res_error(conname, res, "could not open cursor", fail);
-			DBLINK_RES_ERROR("sql error");
+		PG_RETURN_TEXT_P(cstring_to_text("ERROR"));
-		else
-		{
-			DBLINK_RES_ERROR_AS_NOTICE("sql error");
-			PG_RETURN_TEXT_P(cstring_to_text("ERROR"));
-		}
 	}
 
 	PQclear(res);
@@ -470,13 +452,8 @@ dblink_close(PG_FUNCTION_ARGS)
 	res = PQexec(conn, buf.data);
 	if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
 	{
-		if (fail)
+		dblink_res_error(conname, res, "could not close cursor", fail);
-			DBLINK_RES_ERROR("sql error");
+		PG_RETURN_TEXT_P(cstring_to_text("ERROR"));
-		else
-		{
-			DBLINK_RES_ERROR_AS_NOTICE("sql error");
-			PG_RETURN_TEXT_P(cstring_to_text("ERROR"));
-		}
 	}
 
 	PQclear(res);
@@ -513,7 +490,6 @@ dblink_fetch(PG_FUNCTION_ARGS)
 	int			call_cntr;
 	int			max_calls;
 	AttInMetadata *attinmeta;
-	char	   *msg;
 	PGresult   *res = NULL;
 	MemoryContext oldcontext;
 	char	   *conname = NULL;
@@ -590,13 +566,8 @@ dblink_fetch(PG_FUNCTION_ARGS)
 			(PQresultStatus(res) != PGRES_COMMAND_OK &&
 			 PQresultStatus(res) != PGRES_TUPLES_OK))
 		{
-			if (fail)
+			dblink_res_error(conname, res, "could not fetch from cursor", fail);
-				DBLINK_RES_ERROR("sql error");
+			SRF_RETURN_DONE(funcctx);
-			else
-			{
-				DBLINK_RES_ERROR_AS_NOTICE("sql error");
-				SRF_RETURN_DONE(funcctx);
-			}
 		}
 		else if (PQresultStatus(res) == PGRES_COMMAND_OK)
 		{
@@ -846,15 +817,10 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async, bool do_get)
 				(PQresultStatus(res) != PGRES_COMMAND_OK &&
 				 PQresultStatus(res) != PGRES_TUPLES_OK))
 			{
-				if (fail)
+				dblink_res_error(conname, res, "could not execute query", fail);
-					DBLINK_RES_ERROR("sql error");
+				if (freeconn)
-				else
+					PQfinish(conn);
-				{
+				SRF_RETURN_DONE(funcctx);
-					DBLINK_RES_ERROR_AS_NOTICE("sql error");
-					if (freeconn)
-						PQfinish(conn);
-					SRF_RETURN_DONE(funcctx);
-				}
 			}
 
 			if (PQresultStatus(res) == PGRES_COMMAND_OK)
@@ -1180,10 +1146,7 @@ dblink_exec(PG_FUNCTION_ARGS)
 		(PQresultStatus(res) != PGRES_COMMAND_OK &&
 		 PQresultStatus(res) != PGRES_TUPLES_OK))
 	{
-		if (fail)
+		dblink_res_error(conname, res, "could not execute command", fail);
-			DBLINK_RES_ERROR("sql error");
-		else
-			DBLINK_RES_ERROR_AS_NOTICE("sql error");
 
 		/* need a tuple descriptor representing one TEXT column */
 		tupdesc = CreateTemplateTupleDesc(1, false);
@@ -1195,7 +1158,6 @@ dblink_exec(PG_FUNCTION_ARGS)
 		 * result tuple
 		 */
 		sql_cmd_status = cstring_to_text("ERROR");
-
 	}
 	else if (PQresultStatus(res) == PGRES_COMMAND_OK)
 	{
@@ -2288,3 +2250,54 @@ dblink_security_check(PGconn *conn, remoteConn *rconn)
 		}
 	}
 }
+
+static void
+dblink_res_error(const char *conname, PGresult *res, const char *dblink_context_msg, bool fail)
+{
+	int			level;
+	char	   *pg_diag_sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
+	char	   *pg_diag_message_primary = PQresultErrorField(res, PG_DIAG_MESSAGE_PRIMARY);
+	char	   *pg_diag_message_detail = PQresultErrorField(res, PG_DIAG_MESSAGE_DETAIL);
+	char	   *pg_diag_message_hint = PQresultErrorField(res, PG_DIAG_MESSAGE_HINT);
+	char	   *pg_diag_context = PQresultErrorField(res, PG_DIAG_CONTEXT);
+	int			sqlstate;
+	char	   *message_primary;
+	char	   *message_detail;
+	char	   *message_hint;
+	char	   *message_context;
+	const char *dblink_context_conname = "unnamed";
+
+	if (fail)
+		level = ERROR;
+	else
+		level = NOTICE;
+
+	if (pg_diag_sqlstate)
+		sqlstate = MAKE_SQLSTATE(pg_diag_sqlstate[0],
+								 pg_diag_sqlstate[1],
+								 pg_diag_sqlstate[2],
+								 pg_diag_sqlstate[3],
+								 pg_diag_sqlstate[4]);
+	else
+		sqlstate = ERRCODE_CONNECTION_FAILURE;
+
+	xpstrdup(message_primary, pg_diag_message_primary);
+	xpstrdup(message_detail, pg_diag_message_detail);
+	xpstrdup(message_hint, pg_diag_message_hint);
+	xpstrdup(message_context, pg_diag_context);
+
+	if (res)
+		PQclear(res);
+
+	if (conname)
+		dblink_context_conname = conname;
+
+	ereport(level,
+		(errcode(sqlstate),
+		 message_primary ? errmsg("%s", message_primary) : errmsg("unknown error"),
+		 message_detail ? errdetail("%s", message_detail) : 0,
+		 message_hint ? errhint("%s", message_hint) : 0,
+		 message_context ? errcontext("%s", message_context) : 0,
+		 errcontext("Error occurred on dblink connection named \"%s\": %s.",
+					dblink_context_conname, dblink_context_msg)));
+}

contrib/dblink/expected/dblink.out

@@ -125,9 +125,8 @@ WHERE t.a > 7;
 
 -- open a cursor with bad SQL and fail_on_error set to false
 SELECT dblink_open('rmt_foo_cursor','SELECT * FROM foobar',false);
-NOTICE:  sql error
+NOTICE:  relation "foobar" does not exist
-DETAIL:  ERROR:  relation "foobar" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not open cursor.
-
  dblink_open 
 -------------
  ERROR
@@ -194,9 +193,8 @@ FROM dblink_fetch('rmt_foo_cursor',4) AS t(a int, b text, c text[]);
 -- intentionally botch a fetch
 SELECT *
 FROM dblink_fetch('rmt_foobar_cursor',4,false) AS t(a int, b text, c text[]);
-NOTICE:  sql error
+NOTICE:  cursor "rmt_foobar_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foobar_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not fetch from cursor.
-
  a | b | c 
 ---+---+---
 (0 rows)
@@ -210,9 +208,8 @@ SELECT dblink_exec('ABORT');
 
 -- close the wrong cursor
 SELECT dblink_close('rmt_foobar_cursor',false);
-NOTICE:  sql error
+NOTICE:  cursor "rmt_foobar_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foobar_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not close cursor.
-
  dblink_close 
 --------------
  ERROR
@@ -221,15 +218,13 @@ DETAIL:  ERROR:  cursor "rmt_foobar_cursor" does not exist
 -- should generate 'cursor "rmt_foo_cursor" not found' error
 SELECT *
 FROM dblink_fetch('rmt_foo_cursor',4) AS t(a int, b text, c text[]);
-ERROR:  sql error
+ERROR:  cursor "rmt_foo_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foo_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not fetch from cursor.
-
 -- this time, 'cursor "rmt_foo_cursor" not found' as a notice
 SELECT *
 FROM dblink_fetch('rmt_foo_cursor',4,false) AS t(a int, b text, c text[]);
-NOTICE:  sql error
+NOTICE:  cursor "rmt_foo_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foo_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not fetch from cursor.
-
  a | b | c 
 ---+---+---
 (0 rows)
@@ -291,9 +286,8 @@ FROM dblink('SELECT * FROM foo') AS t(a int, b text, c text[]);
 -- bad remote select
 SELECT *
 FROM dblink('SELECT * FROM foobar',false) AS t(a int, b text, c text[]);
-NOTICE:  sql error
+NOTICE:  relation "foobar" does not exist
-DETAIL:  ERROR:  relation "foobar" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not execute query.
-
  a | b | c 
 ---+---+---
 (0 rows)
@@ -316,9 +310,8 @@ WHERE a = 11;
 
 -- botch a change to some other data
 SELECT dblink_exec('UPDATE foobar SET f3[2] = ''b99'' WHERE f1 = 11',false);
-NOTICE:  sql error
+NOTICE:  relation "foobar" does not exist
-DETAIL:  ERROR:  relation "foobar" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not execute command.
-
  dblink_exec 
 -------------
  ERROR
@@ -378,9 +371,8 @@ WHERE t.a > 7;
 SELECT *
 FROM dblink('myconn','SELECT * FROM foobar',false) AS t(a int, b text, c text[])
 WHERE t.a > 7;
-NOTICE:  sql error
+NOTICE:  relation "foobar" does not exist
-DETAIL:  ERROR:  relation "foobar" does not exist
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not execute query.
-
  a | b | c 
 ---+---+---
 (0 rows)
@@ -416,9 +408,8 @@ SELECT dblink_disconnect('myconn2');
 
 -- open a cursor incorrectly
 SELECT dblink_open('myconn','rmt_foo_cursor','SELECT * FROM foobar',false);
-NOTICE:  sql error
+NOTICE:  relation "foobar" does not exist
-DETAIL:  ERROR:  relation "foobar" does not exist
+CONTEXT:  Error occurred on dblink connection named "myconn": could not open cursor.
-
  dblink_open 
 -------------
  ERROR
@@ -503,9 +494,8 @@ SELECT dblink_close('myconn','rmt_foo_cursor');
 
 -- this should fail because there is no open transaction
 SELECT dblink_exec('myconn','DECLARE xact_test CURSOR FOR SELECT * FROM foo');
-ERROR:  sql error
+ERROR:  DECLARE CURSOR can only be used in transaction blocks
-DETAIL:  ERROR:  DECLARE CURSOR can only be used in transaction blocks
+CONTEXT:  Error occurred on dblink connection named "unnamed": could not execute command.
-
 -- reset remote transaction state
 SELECT dblink_exec('myconn','ABORT');
  dblink_exec 
@@ -554,9 +544,8 @@ FROM dblink_fetch('myconn','rmt_foo_cursor',4) AS t(a int, b text, c text[]);
 -- fetch some data incorrectly
 SELECT *
 FROM dblink_fetch('myconn','rmt_foobar_cursor',4,false) AS t(a int, b text, c text[]);
-NOTICE:  sql error
+NOTICE:  cursor "rmt_foobar_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foobar_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "myconn": could not fetch from cursor.
-
  a | b | c 
 ---+---+---
 (0 rows)
@@ -571,9 +560,8 @@ SELECT dblink_exec('myconn','ABORT');
 -- should generate 'cursor "rmt_foo_cursor" not found' error
 SELECT *
 FROM dblink_fetch('myconn','rmt_foo_cursor',4) AS t(a int, b text, c text[]);
-ERROR:  sql error
+ERROR:  cursor "rmt_foo_cursor" does not exist
-DETAIL:  ERROR:  cursor "rmt_foo_cursor" does not exist
+CONTEXT:  Error occurred on dblink connection named "myconn": could not fetch from cursor.
-
 -- close the named persistent connection
 SELECT dblink_disconnect('myconn');
  dblink_disconnect