psql: Show notices immediately (again)

The new show-all-results feature in psql (7844c99) went out of its
way to show notices next to the results of the statements (in a
multi-statement string) that caused them.  This also had the
consequence that notices for a single statement were not shown until
after the statement had executed, instead of right away.  After some
discussion, it seems very difficult to satisfy both of these goals, so
here we are giving up on the first goal and just show the notices as
we get them.  This restores the pre-7844c9918 behavior for notices.

Reported-by: Alastair McKinley <a.mckinley@analyticsengines.com>
Author: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: https://www.postgresql.org/message-id/flat/PAXPR02MB760039506C87A2083AD85575E3DA9%40PAXPR02MB7600.eurprd02.prod.outlook.com

Author: petere

src/bin/psql/common.c

@@ -1061,44 +1061,6 @@ PrintQueryResult(PGresult *result, bool last, bool is_watch, const printQueryOpt
 	return success;
 }
 
-/*
- * Data structure and functions to record notices while they are
- * emitted, so that they can be shown later.
- *
- * We need to know which result is last, which requires to extract
- * one result in advance, hence two buffers are needed.
- */
-struct t_notice_messages
-{
-	PQExpBufferData messages[2];
-	int			current;
-};
-
-/*
- * Store notices in appropriate buffer, for later display.
- */
-static void
-AppendNoticeMessage(void *arg, const char *msg)
-{
-	struct t_notice_messages *notices = arg;
-
-	appendPQExpBufferStr(&notices->messages[notices->current], msg);
-}
-
-/*
- * Show notices stored in buffer, which is then reset.
- */
-static void
-ShowNoticeMessage(struct t_notice_messages *notices)
-{
-	PQExpBufferData *current = &notices->messages[notices->current];
-
-	if (*current->data != '\0')
-		pg_log_info("%s", current->data);
-	resetPQExpBuffer(current);
-}
-
-
 /*
  * SendQuery: send the query string to the backend
  * (and print out result)
@@ -1483,7 +1445,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 	instr_time	before,
 				after;
 	PGresult   *result;
-	struct t_notice_messages notices;
 
 	if (timing)
 		INSTR_TIME_SET_CURRENT(before);
@@ -1513,12 +1474,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 		return 0;
 	}
 
-	/* intercept notices */
-	notices.current = 0;
-	initPQExpBuffer(&notices.messages[0]);
-	initPQExpBuffer(&notices.messages[1]);
-	PQsetNoticeProcessor(pset.db, AppendNoticeMessage, &notices);
-
 	/* first result */
 	result = PQgetResult(pset.db);
 
@@ -1536,7 +1491,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 			 */
 			const char *error = PQresultErrorMessage(result);
 
-			ShowNoticeMessage(&notices);
 			if (strlen(error))
 				pg_log_info("%s", error);
 
@@ -1601,31 +1555,22 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 		if (result_status == PGRES_COPY_IN ||
 			result_status == PGRES_COPY_OUT)
 		{
-			ShowNoticeMessage(&notices);
-
 			if (is_watch)
 			{
 				ClearOrSaveAllResults();
 				pg_log_error("\\watch cannot be used with COPY");
 				return -1;
 			}
 
-			/* use normal notice processor during COPY */
-			PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL);
-
 			success &= HandleCopyResult(&result);
-
-			PQsetNoticeProcessor(pset.db, AppendNoticeMessage, &notices);
 		}
 
 		/*
 		 * Check PQgetResult() again.  In the typical case of a single-command
 		 * string, it will return NULL.  Otherwise, we'll have other results
 		 * to process.  We need to do that to check whether this is the last.
 		 */
-		notices.current ^= 1;
 		next_result = PQgetResult(pset.db);
-		notices.current ^= 1;
 		last = (next_result == NULL);
 
 		/*
@@ -1647,9 +1592,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 			*elapsed_msec = INSTR_TIME_GET_MILLISEC(after);
 		}
 
-		/* notices already shown above for copy */
-		ShowNoticeMessage(&notices);
-
 		/* this may or may not print something depending on settings */
 		if (result != NULL)
 			success &= PrintQueryResult(result, last, false, opt, printQueryFout);
@@ -1659,7 +1601,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 			SetResultVariables(result, true);
 
 		ClearOrSaveResult(result);
-		notices.current ^= 1;
 		result = next_result;
 
 		if (cancel_pressed)
@@ -1669,11 +1610,6 @@ ExecQueryAndProcessResults(const char *query, double *elapsed_msec, bool *svpt_g
 		}
 	}
 
-	/* reset notice hook */
-	PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL);
-	termPQExpBuffer(&notices.messages[0]);
-	termPQExpBuffer(&notices.messages[1]);
-
 	/* may need this to recover from conn loss during COPY */
 	if (!CheckConnection())
 		return -1;

src/test/regress/expected/psql.out

@@ -5316,13 +5316,13 @@ AS $$
 $$;
 -- show both
 SELECT 1 AS one \; SELECT warn('1.5') \; SELECT 2 AS two ;
+NOTICE:  warn 1.5
+CONTEXT:  PL/pgSQL function warn(text) line 2 at RAISE
  one 
 -----
    1
 (1 row)
 
-NOTICE:  warn 1.5
-CONTEXT:  PL/pgSQL function warn(text) line 2 at RAISE
  warn 
 ------
  t
@@ -5335,13 +5335,13 @@ CONTEXT:  PL/pgSQL function warn(text) line 2 at RAISE
 
 -- \gset applies to last query only
 SELECT 3 AS three \; SELECT warn('3.5') \; SELECT 4 AS four \gset
+NOTICE:  warn 3.5
+CONTEXT:  PL/pgSQL function warn(text) line 2 at RAISE
  three 
 -------
      3
 (1 row)
 
-NOTICE:  warn 3.5
-CONTEXT:  PL/pgSQL function warn(text) line 2 at RAISE
  warn 
 ------
  t