diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 76f48b13d2..217910c9de 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -1068,11 +1068,14 @@ exec_simple_query(const char *query_string)
 	/* Log immediately if dictated by log_statement */
 	if (check_log_statement(parsetree_list))
 	{
-		ereport(LOG,
-				(errmsg("statement: %s", query_string),
-				 errhidestmt(true),
-				 errdetail_execute(parsetree_list)));
-		was_logged = true;
+		if (!Log_has_xid || TransactionIdIsValid(GetTopTransactionIdIfAny()))
+		{
+			ereport(LOG,
+					(errmsg("statement: %s", query_string),
+					errhidestmt(true),
+					errdetail_execute(parsetree_list)));
+			was_logged = true;
+		}
 	}
 
 	/*
@@ -1283,6 +1286,16 @@ exec_simple_query(const char *query_string)
 
 		PortalDrop(portal, false);
 
+		/* Log if dictated by log_statement and has not been logged. */
+		if (!was_logged && check_log_statement(parsetree_list))
+		{
+			ereport(LOG,
+					(errmsg("statement: %s", query_string),
+					errhidestmt(true),
+					errdetail_execute(parsetree_list)));
+			was_logged = true;
+		}
+
 		if (lnext(parsetree_list, parsetree_item) == NULL)
 		{
 			/*
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 605ff3b045..e7dd9f5027 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -79,6 +79,7 @@
 #include "storage/ipc.h"
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
+#include "utils/guc.h"
 #include "utils/guc_hooks.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
@@ -114,6 +115,9 @@ char	   *Log_destination_string = NULL;
 bool		syslog_sequence_numbers = true;
 bool		syslog_split_messages = true;
 
+/* Whether the transaction id will appear in the log messages. */
+bool		Log_has_xid = false;
+
 /* Processed form of backtrace_functions GUC */
 static char *backtrace_function_list;
 
@@ -286,6 +290,50 @@ message_level_is_interesting(int elevel)
 }
 
 
+/*
+ * check_log_line_prefix: GUC check_hook for Log_line_prefix
+ */
+bool check_log_line_prefix(char **newval, void **extra, GucSource source)
+{
+	const char *p;
+
+	if ((*newval) == NULL)
+	{
+		Log_has_xid = false;
+		return true;
+	}
+
+	Log_has_xid = false;
+
+	for (p = (*newval); *p != '\0'; p++)
+	{
+		if (*p != '%')
+		{
+			/* literal char, just skip */
+			continue;
+		}
+
+		/* must be a '%', so skip to the next char */
+		p++;
+		if (*p == '\0')
+			break;				/* format error - ignore it */
+		else if (*p == '%')
+		{
+			/* string contains %% */
+			continue;
+		}
+
+		/* process the option */
+		if (*p == 'x')
+		{
+			Log_has_xid = true;
+			break;
+		}
+	}
+
+	return true;
+}
+
 /*
  * in_error_recursion_trouble --- are we at risk of infinite error recursion?
  *
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index c68fdc008b..96948e5005 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -4103,7 +4103,7 @@ struct config_string ConfigureNamesString[] =
 		},
 		&Log_line_prefix,
 		"%m [%p] ",
-		NULL, NULL, NULL
+		check_log_line_prefix, NULL, NULL
 	},
 
 	{
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 054dd2bf62..9536146ce3 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -502,6 +502,8 @@ extern PGDLLIMPORT char *Log_destination_string;
 extern PGDLLIMPORT bool syslog_sequence_numbers;
 extern PGDLLIMPORT bool syslog_split_messages;
 
+extern PGDLLIMPORT bool	Log_has_xid;
+
 /* Log destination bitmap */
 #define LOG_DESTINATION_STDERR	 1
 #define LOG_DESTINATION_SYSLOG	 2
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index d64dc5fcdb..41f8ba3f16 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -78,6 +78,7 @@ extern bool check_log_destination(char **newval, void **extra,
 extern void assign_log_destination(const char *newval, void *extra);
 extern const char *show_log_file_mode(void);
 extern bool check_log_stats(bool *newval, void **extra, GucSource source);
+extern bool check_log_line_prefix(char **newval, void **extra, GucSource source);
 extern bool check_log_timezone(char **newval, void **extra, GucSource source);
 extern void assign_log_timezone(const char *newval, void *extra);
 extern const char *show_log_timezone(void);