Keep username and datname empty if we cannot get real values

If transaction state is not 'in progress' than we cannot do database
access. For that case we should keep username and datname just empty
instad of filling them with error message.

Also we can improve collecting these fields by grabbing them early in
utillity hook, when transaction state wasn't yet changed by actual hook
processing.

Author: artemgavrilov

pg_stat_monitor.c

@@ -1018,7 +1018,6 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
 		!IsA(parsetree, PrepareStmt) &&
 		!IsA(parsetree, DeallocateStmt))
 	{
-		pgsmEntry  *entry;
 		char	   *query_text;
 		int			location;
 		int			query_len;
@@ -1030,6 +1029,7 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
 		BufferUsage bufusage_start = pgBufferUsage;
 		WalUsage	walusage;
 		WalUsage	walusage_start = pgWalUsage;
+		pgsmEntry  *entry = pgsm_create_hash_entry(0, queryId, NULL);;
 
 		if (getrusage(RUSAGE_SELF, &rusage_start) != 0)
 			elog(DEBUG1, "[pg_stat_monitor] pgsm_ProcessUtility: Failed to execute getrusage.");
@@ -1090,9 +1090,6 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
 		memset(&bufusage, 0, sizeof(BufferUsage));
 		BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
 
-		/* Create an entry for this query */
-		entry = pgsm_create_hash_entry(0, queryId, NULL);
-
 		location = pstmt->stmt_location;
 		query_len = pstmt->stmt_len;
 		query_text = (char *) CleanQuerytext(queryString, &location, &query_len);
@@ -1743,19 +1740,16 @@ pgsm_create_hash_entry(uint64 bucket_id, int64 queryid, PlanInfo *plan_info)
 	{
 		datname = get_database_name(entry->key.dbid);
 		username = GetUserNameFromId(entry->key.userid, true);
-	}
 
-	if (!datname)
-		datname = pnstrdup("<database name not available>", sizeof(entry->datname) - 1);
+		snprintf(entry->datname, sizeof(entry->datname), "%s", datname);
+		snprintf(entry->username, sizeof(entry->username), "%s", username);
 
-	if (!username)
-		username = pnstrdup("<user name not available>", sizeof(entry->username) - 1);
+		if (datname)
+			pfree(datname);
 
-	snprintf(entry->datname, sizeof(entry->datname), "%s", datname);
-	snprintf(entry->username, sizeof(entry->username), "%s", username);
-
-	pfree(datname);
-	pfree(username);
+		if (username)
+			pfree(username);
+	}
 
 	MemoryContextSwitchTo(oldctx);
 

regression/expected/application_name_unique.out

@@ -25,8 +25,8 @@ SELECT query,application_name FROM pg_stat_monitor ORDER BY query, application_n
  SELECT 1 AS num                | naeem
  SELECT 1 AS num                | psql
  SELECT pg_stat_monitor_reset() | pg_regress/application_name_unique
- SET application_name = 'naeem' | naeem
- SET application_name = 'psql'  | psql
+ SET application_name = 'naeem' | pg_regress/application_name_unique
+ SET application_name = 'psql'  | naeem
 (5 rows)
 
 SELECT pg_stat_monitor_reset();

regression/expected/user.out

@@ -39,15 +39,15 @@ SELECT username, query FROM pg_stat_monitor ORDER BY username, query COLLATE "C"
  su       | DROP OWNED BY u2
  su       | DROP USER u2
  su       | SELECT pg_stat_monitor_reset()
- su       | SET ROLE su
+ su       | SET ROLE u1
  u1       | CREATE TABLE t1 (a int)
  u1       | SELECT * FROM t1
  u1       | SELECT pg_stat_monitor_reset();
- u1       | SET ROLE u1
+ u1       | SET ROLE u2
  u2       | CREATE TABLE t2 (a int)
  u2       | DROP TABLE t2
  u2       | SELECT * FROM t2
- u2       | SET ROLE u2
+ u2       | SET ROLE su
 (12 rows)
 
 SELECT pg_stat_monitor_reset();