Hello.
I'm occasionally annoyed by the behavior of pg_waldump that it shows
all records in the specified segment before entering waiting state.
tail -f shows only the last few dozen lines at the start. This
behavior I think is useful also for pg_waldump -f.
It was as simple than expected as attached.
Any thoughts, opinions?
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 31e99c2a6d..dacdb600bf 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -72,6 +72,8 @@ typedef struct XLogDumpStats
#define fatal_error(...) do { pg_log_fatal(__VA_ARGS__); exit(EXIT_FAILURE); } while(0)
+#define FOLLOW_START_LINES 20
+
static void
print_rmgr_list(void)
{
@@ -752,6 +754,10 @@ main(int argc, char **argv)
XLogRecPtr first_record;
char *waldir = NULL;
char *errormsg;
+ XLogRecPtr last_recs[FOLLOW_START_LINES];
+ int last_idx = 0;
+ bool storing;
+ bool rounded;
static struct option long_options[] = {
{"bkp-details", no_argument, NULL, 'b'},
@@ -1065,10 +1071,41 @@ main(int argc, char **argv)
(uint32) (first_record >> 32), (uint32) first_record,
(uint32) (first_record - private.startptr));
+ storing = config.follow;
+ rounded = false;
+
for (;;)
{
/* try to read the next record */
record = XLogReadRecord(xlogreader_state, &errormsg);
+
+ if (storing)
+ {
+ if (record)
+ {
+ /* remember LSNs of the last FOLLOW_START_LINES records */
+ last_recs[last_idx++] = xlogreader_state->ReadRecPtr;
+ last_idx = last_idx % FOLLOW_START_LINES;
+
+ if (last_idx == 0)
+ rounded = true;
+ }
+ else
+ {
+ XLogRecPtr startPtr;
+
+ /* find the first record to show */
+ if (!rounded)
+ startPtr = last_recs[0];
+ else
+ startPtr = last_recs[last_idx];
+
+ XLogFindNextRecord(xlogreader_state, startPtr);
+ storing = false;
+ }
+ continue;
+ }
+
if (!record)
{
if (!config.follow || private.endptr_reached)
