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Commit24ff700

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Code review for commit05a7be9.
Avoid having walreceiver code know explicitly about the precisionand underlying datatype of TimestampTz. (There is still onecalculation that knows that, which should be replaced with use ofTimestampDifferenceMilliseconds; but we need to figure out what to doabout overflow cases first.)In support of this, provide a TimestampTzPlusSeconds macro, as wellas TIMESTAMP_INFINITY and TIMESTAMP_MINUS_INFINITY macros. (We couldhave used the existing DT_NOEND and DT_NOBEGIN symbols, but I judgedthose too opaque and confusing.)Move GetCurrentTimestamp calls so that it's more obvious that weare not using stale values of "now" anyplace. This doesn't resultin net more calls, and might indeed make for net fewer.Avoid having a dummy value in the WalRcvWakeupReason enum, so thatwe can hope for the compiler to catch overlooked switch cases.Nathan Bossart and Tom LaneDiscussion:https://postgr.es/m/20230125235004.GA1327755@nathanxps13
1 parente35bb9f commit24ff700

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3 files changed

+36
-26
lines changed

3 files changed

+36
-26
lines changed

‎src/backend/replication/walreceiver.c

Lines changed: 24 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -122,8 +122,8 @@ typedef enum WalRcvWakeupReason
122122
WALRCV_WAKEUP_TERMINATE,
123123
WALRCV_WAKEUP_PING,
124124
WALRCV_WAKEUP_REPLY,
125-
WALRCV_WAKEUP_HSFEEDBACK,
126-
NUM_WALRCV_WAKEUPS
125+
WALRCV_WAKEUP_HSFEEDBACK
126+
#defineNUM_WALRCV_WAKEUPS (WALRCV_WAKEUP_HSFEEDBACK+1)
127127
}WalRcvWakeupReason;
128128

129129
/*
@@ -206,8 +206,6 @@ WalReceiverMain(void)
206206
*/
207207
Assert(walrcv!=NULL);
208208

209-
now=GetCurrentTimestamp();
210-
211209
/*
212210
* Mark walreceiver as running in shared memory.
213211
*
@@ -261,6 +259,7 @@ WalReceiverMain(void)
261259
Assert(!is_temp_slot|| (slotname[0]=='\0'));
262260

263261
/* Initialise to a sanish value */
262+
now=GetCurrentTimestamp();
264263
walrcv->lastMsgSendTime=
265264
walrcv->lastMsgReceiptTime=walrcv->latestWalEndTime=now;
266265

@@ -464,6 +463,7 @@ WalReceiverMain(void)
464463
{
465464
ConfigReloadPending= false;
466465
ProcessConfigFile(PGC_SIGHUP);
466+
/* recompute wakeup times */
467467
now=GetCurrentTimestamp();
468468
for (inti=0;i<NUM_WALRCV_WAKEUPS;++i)
469469
WalRcvComputeNextWakeup(i,now);
@@ -472,7 +472,6 @@ WalReceiverMain(void)
472472

473473
/* See if we can read data immediately */
474474
len=walrcv_receive(wrconn,&buf,&wait_fd);
475-
now=GetCurrentTimestamp();
476475
if (len!=0)
477476
{
478477
/*
@@ -487,6 +486,7 @@ WalReceiverMain(void)
487486
* Something was received from primary, so adjust
488487
* the ping and terminate wakeup times.
489488
*/
489+
now=GetCurrentTimestamp();
490490
WalRcvComputeNextWakeup(WALRCV_WAKEUP_TERMINATE,
491491
now);
492492
WalRcvComputeNextWakeup(WALRCV_WAKEUP_PING,now);
@@ -506,7 +506,6 @@ WalReceiverMain(void)
506506
break;
507507
}
508508
len=walrcv_receive(wrconn,&buf,&wait_fd);
509-
now=GetCurrentTimestamp();
510509
}
511510

512511
/* Let the primary know that we received some data. */
@@ -525,7 +524,7 @@ WalReceiverMain(void)
525524
break;
526525

527526
/* Find the soonest wakeup time, to limit our nap. */
528-
nextWakeup=PG_INT64_MAX;
527+
nextWakeup=TIMESTAMP_INFINITY;
529528
for (inti=0;i<NUM_WALRCV_WAKEUPS;++i)
530529
nextWakeup=Min(wakeup[i],nextWakeup);
531530

@@ -536,6 +535,7 @@ WalReceiverMain(void)
536535
* millisecond to avoid waking up too early and spinning until
537536
* one of the wakeup times.
538537
*/
538+
now=GetCurrentTimestamp();
539539
nap= (int)Min(INT_MAX,Max(0, (nextWakeup-now+999) /1000));
540540

541541
/*
@@ -556,7 +556,6 @@ WalReceiverMain(void)
556556
wait_fd,
557557
nap,
558558
WAIT_EVENT_WAL_RECEIVER_MAIN);
559-
now=GetCurrentTimestamp();
560559
if (rc&WL_LATCH_SET)
561560
{
562561
ResetLatch(MyLatch);
@@ -592,19 +591,20 @@ WalReceiverMain(void)
592591
* Check if time since last receive from primary has
593592
* reached the configured limit.
594593
*/
594+
now=GetCurrentTimestamp();
595595
if (now >=wakeup[WALRCV_WAKEUP_TERMINATE])
596596
ereport(ERROR,
597597
(errcode(ERRCODE_CONNECTION_FAILURE),
598598
errmsg("terminating walreceiver due to timeout")));
599599

600600
/*
601-
*Wedidn't receive anything new, for half of receiver
602-
* replication timeout. Ping the server.
601+
*If wedidn't receive anything new for half of receiver
602+
* replication timeout, then ping the server.
603603
*/
604604
if (now >=wakeup[WALRCV_WAKEUP_PING])
605605
{
606606
requestReply= true;
607-
wakeup[WALRCV_WAKEUP_PING]=PG_INT64_MAX;
607+
wakeup[WALRCV_WAKEUP_PING]=TIMESTAMP_INFINITY;
608608
}
609609

610610
XLogWalRcvSendReply(requestReply,requestReply);
@@ -1266,7 +1266,6 @@ static void
12661266
ProcessWalSndrMessage(XLogRecPtrwalEnd,TimestampTzsendTime)
12671267
{
12681268
WalRcvData*walrcv=WalRcv;
1269-
12701269
TimestampTzlastMsgReceiptTime=GetCurrentTimestamp();
12711270

12721271
/* Update shared-memory status */
@@ -1310,7 +1309,10 @@ ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime)
13101309
/*
13111310
* Compute the next wakeup time for a given wakeup reason. Can be called to
13121311
* initialize a wakeup time, to adjust it for the next wakeup, or to
1313-
* reinitialize it when GUCs have changed.
1312+
* reinitialize it when GUCs have changed. We ask the caller to pass in the
1313+
* value of "now" because this frequently avoids multiple calls of
1314+
* GetCurrentTimestamp(). It had better be a reasonably up-to-date value
1315+
* though.
13141316
*/
13151317
staticvoid
13161318
WalRcvComputeNextWakeup(WalRcvWakeupReasonreason,TimestampTznow)
@@ -1319,30 +1321,29 @@ WalRcvComputeNextWakeup(WalRcvWakeupReason reason, TimestampTz now)
13191321
{
13201322
caseWALRCV_WAKEUP_TERMINATE:
13211323
if (wal_receiver_timeout <=0)
1322-
wakeup[reason]=PG_INT64_MAX;
1324+
wakeup[reason]=TIMESTAMP_INFINITY;
13231325
else
1324-
wakeup[reason]=now+wal_receiver_timeout*INT64CONST(1000);
1326+
wakeup[reason]=TimestampTzPlusMilliseconds(now,wal_receiver_timeout);
13251327
break;
13261328
caseWALRCV_WAKEUP_PING:
13271329
if (wal_receiver_timeout <=0)
1328-
wakeup[reason]=PG_INT64_MAX;
1330+
wakeup[reason]=TIMESTAMP_INFINITY;
13291331
else
1330-
wakeup[reason]=now+ (wal_receiver_timeout /2)*INT64CONST(1000);
1332+
wakeup[reason]=TimestampTzPlusMilliseconds(now,wal_receiver_timeout /2);
13311333
break;
13321334
caseWALRCV_WAKEUP_HSFEEDBACK:
13331335
if (!hot_standby_feedback||wal_receiver_status_interval <=0)
1334-
wakeup[reason]=PG_INT64_MAX;
1336+
wakeup[reason]=TIMESTAMP_INFINITY;
13351337
else
1336-
wakeup[reason]=now+wal_receiver_status_interval*INT64CONST(1000000);
1338+
wakeup[reason]=TimestampTzPlusSeconds(now,wal_receiver_status_interval);
13371339
break;
13381340
caseWALRCV_WAKEUP_REPLY:
13391341
if (wal_receiver_status_interval <=0)
1340-
wakeup[reason]=PG_INT64_MAX;
1342+
wakeup[reason]=TIMESTAMP_INFINITY;
13411343
else
1342-
wakeup[reason]=now+wal_receiver_status_interval*INT64CONST(1000000);
1343-
break;
1344-
default:
1344+
wakeup[reason]=TimestampTzPlusSeconds(now,wal_receiver_status_interval);
13451345
break;
1346+
/* there's intentionally no default: here */
13461347
}
13471348
}
13481349

‎src/include/datatype/timestamp.h

Lines changed: 10 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -143,10 +143,17 @@ struct pg_itm_in
143143
#defineTZDISP_LIMIT((MAX_TZDISP_HOUR + 1) * SECS_PER_HOUR)
144144

145145
/*
146-
* DT_NOBEGIN represents timestamp -infinity; DT_NOEND represents +infinity
146+
* We reserve the minimum and maximum integer values to represent
147+
* timestamp (or timestamptz) -infinity and +infinity.
147148
*/
148-
#defineDT_NOBEGINPG_INT64_MIN
149-
#defineDT_NOENDPG_INT64_MAX
149+
#defineTIMESTAMP_MINUS_INFINITYPG_INT64_MIN
150+
#defineTIMESTAMP_INFINITYPG_INT64_MAX
151+
152+
/*
153+
* Historically these alias for infinity have been used.
154+
*/
155+
#defineDT_NOBEGINTIMESTAMP_MINUS_INFINITY
156+
#defineDT_NOENDTIMESTAMP_INFINITY
150157

151158
#defineTIMESTAMP_NOBEGIN(j)\
152159
do {(j) = DT_NOBEGIN;} while (0)

‎src/include/utils/timestamp.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -81,7 +81,9 @@ IntervalPGetDatum(const Interval *X)
8181
#defineINTERVAL_PRECISION(t) ((t) & INTERVAL_PRECISION_MASK)
8282
#defineINTERVAL_RANGE(t) (((t) >> 16) & INTERVAL_RANGE_MASK)
8383

84+
/* Macros for doing timestamp arithmetic without assuming timestamp's units */
8485
#defineTimestampTzPlusMilliseconds(tz,ms) ((tz) + ((ms) * (int64) 1000))
86+
#defineTimestampTzPlusSeconds(tz,s) ((tz) + ((s) * (int64) 1000000))
8587

8688

8789
/* Set at postmaster start */

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