Teach walsender to update its process title for replication commands.

Because the code path taken for SQL commands executed in a walsender
will update the process title, we pretty much have to update the
title for replication commands as well.  Otherwise, the title shows
"idle" for the rest of a logical walsender's lifetime once it's
executed any SQL command.

Playing with this, I confirm that a walsender now typically spends
most of its life reporting
	walsender postgres [local] START_REPLICATION
Considering this in isolation, it might be better to have it say
	walsender postgres [local] sending replication data
However, consistency with the other cases seems to be a stronger
argument.

In passing, remove duplicative pgstat_report_activity call.

Discussion: https://postgr.es/m/880181.1600026471@sss.pgh.pa.us

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c1b5ad35deb5b86e31a30f6a687c6a4acf67f3e2..7c9d1b67dfbd5747272f276a2a61f08299270146 100644 (file)
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1616,12 +1616,14 @@ exec_replication_command(const char *cmd_string)
    {
        case T_IdentifySystemCmd:
            cmdtag = "IDENTIFY_SYSTEM";
+           set_ps_display(cmdtag);
            IdentifySystem();
            EndReplicationCommand(cmdtag);
            break;
 
        case T_BaseBackupCmd:
            cmdtag = "BASE_BACKUP";
+           set_ps_display(cmdtag);
            PreventInTransactionBlock(true, cmdtag);
            SendBaseBackup((BaseBackupCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
@@ -1629,12 +1631,14 @@ exec_replication_command(const char *cmd_string)
 
        case T_CreateReplicationSlotCmd:
            cmdtag = "CREATE_REPLICATION_SLOT";
+           set_ps_display(cmdtag);
            CreateReplicationSlot((CreateReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_DropReplicationSlotCmd:
            cmdtag = "DROP_REPLICATION_SLOT";
+           set_ps_display(cmdtag);
            DropReplicationSlot((DropReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
@@ -1644,6 +1648,7 @@ exec_replication_command(const char *cmd_string)
                StartReplicationCmd *cmd = (StartReplicationCmd *) cmd_node;
 
                cmdtag = "START_REPLICATION";
+               set_ps_display(cmdtag);
                PreventInTransactionBlock(true, cmdtag);
 
                if (cmd->kind == REPLICATION_KIND_PHYSICAL)
@@ -1659,6 +1664,7 @@ exec_replication_command(const char *cmd_string)
 
        case T_TimeLineHistoryCmd:
            cmdtag = "TIMELINE_HISTORY";
+           set_ps_display(cmdtag);
            PreventInTransactionBlock(true, cmdtag);
            SendTimeLineHistory((TimeLineHistoryCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
@@ -1670,6 +1676,7 @@ exec_replication_command(const char *cmd_string)
                VariableShowStmt *n = (VariableShowStmt *) cmd_node;
 
                cmdtag = "SHOW";
+               set_ps_display(cmdtag);
 
                /* syscache access needs a transaction environment */
                StartTransactionCommand();
@@ -1688,8 +1695,11 @@ exec_replication_command(const char *cmd_string)
    MemoryContextSwitchTo(old_context);
    MemoryContextDelete(cmd_context);
 
-   /* Report to pgstat that this process is now idle */
-   pgstat_report_activity(STATE_IDLE, NULL);
+   /*
+    * We need not update ps display or pg_stat_activity, because PostgresMain
+    * will reset those to "idle".  But we must reset debug_query_string to
+    * ensure it doesn't become a dangling pointer.
+    */
    debug_query_string = NULL;
 
    return true;