Reimplement nullification of walsender timestamp

Make the value null only at pg_stat_activity-output time, as suggested
by Tom Lane, instead of messing with the internal state.  This should
appease buildfarm members with force_parallel_mode=regress, which are
running parallel queries on logical replication walsenders.

The fact that walsenders can run parallel queries should perhaps be
studied more carefully, but for the moment let's get rid of the red
blots in buildfarm.

Backpatch to pg10, like the previous commit.

Discussion: https://postgr.es/m/30804.1578438763@sss.pgh.pa.us

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 075b243183378b33311ffdab3e09666cdac8a087..bd396f0f08fa1e70a7a66b844fa0294d9038149e 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -817,13 +817,6 @@ GetCurrentTransactionStopTimestamp(void)
 void
 SetCurrentStatementStartTimestamp(void)
 {
-   /*
-    * Skip if on a walsender; this is not needed, and it confuses monitoring
-    * if we publish non-NULL values.
-    */
-   if (am_walsender)
-       return;
-
    if (!IsParallelWorker())
        stmtStartTimestamp = GetCurrentTimestamp();
    else

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 05240bfd142c3b0176d254640e81dba4c6cb58bb..93b7814418db72517a80399aacb685fc56f53b0a 100644 (file)
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -726,7 +726,13 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
            else
                nulls[7] = true;
 
-           if (beentry->st_xact_start_timestamp != 0)
+           /*
+            * Don't expose transaction time for walsenders; it confuses
+            * monitoring, particularly because we don't keep the time up-to-
+            * date.
+            */
+           if (beentry->st_xact_start_timestamp != 0 &&
+               beentry->st_backendType != B_WAL_SENDER)
                values[8] = TimestampTzGetDatum(beentry->st_xact_start_timestamp);
            else
                nulls[8] = true;