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);