Show more processes in pg_stat_activity.

Previously, auxiliary processes and background workers not connected
to a database (such as the logical replication launcher) weren't
shown.  Include them, so that we can see the associated wait state
information.  Add a new column to identify the processes type, so that
people can filter them out easily using SQL if they wish.

Before this patch was written, there was discussion about whether we
should expose this information in a separate view, so as to avoid
contaminating pg_stat_activity with things people might not want to
see.  But putting everything in pg_stat_activity was a more popular
choice, so that's what the patch does.

Kuntal Ghosh, reviewed by Amit Langote and Michael Paquier.  Some
revisions and bug fixes by me.

Discussion: http://postgr.es/m/CA+TgmoYES5nhkEGw9nZXU8_FhA8XEm8NTm3-SO+3ML1B81Hkww@mail.gmail.com

1 files changed, 44 insertions, 16 deletions

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index a987d0d6214..dd2b924d0af 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -20,6 +20,7 @@
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/postmaster.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
@@ -538,7 +539,7 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_activity(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_ACTIVITY_COLS	23
+#define PG_STAT_GET_ACTIVITY_COLS	24
 	int			num_backends = pgstat_fetch_stat_numbackends();
 	int			curr_backend;
 	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
@@ -582,8 +583,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 		LocalPgBackendStatus *local_beentry;
 		PgBackendStatus *beentry;
 		PGPROC	   *proc;
-		const char *wait_event_type;
-		const char *wait_event;
+		const char *wait_event_type = NULL;
+		const char *wait_event = NULL;
 
 		MemSet(values, 0, sizeof(values));
 		MemSet(nulls, 0, sizeof(nulls));
@@ -615,9 +616,18 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			continue;
 
 		/* Values available to all callers */
-		values[0] = ObjectIdGetDatum(beentry->st_databaseid);
+		if (beentry->st_databaseid != InvalidOid)
+			values[0] = ObjectIdGetDatum(beentry->st_databaseid);
+		else
+			nulls[0] = true;
+
 		values[1] = Int32GetDatum(beentry->st_procpid);
-		values[2] = ObjectIdGetDatum(beentry->st_userid);
+
+		if (beentry->st_userid != InvalidOid)
+			values[2] = ObjectIdGetDatum(beentry->st_userid);
+		else
+			nulls[2] = true;
+
 		if (beentry->st_appname)
 			values[3] = CStringGetTextDatum(beentry->st_appname);
 		else
@@ -635,17 +645,17 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 
 		if (beentry->st_ssl)
 		{
-			values[17] = BoolGetDatum(true);	/* ssl */
-			values[18] = CStringGetTextDatum(beentry->st_sslstatus->ssl_version);
-			values[19] = CStringGetTextDatum(beentry->st_sslstatus->ssl_cipher);
-			values[20] = Int32GetDatum(beentry->st_sslstatus->ssl_bits);
-			values[21] = BoolGetDatum(beentry->st_sslstatus->ssl_compression);
-			values[22] = CStringGetTextDatum(beentry->st_sslstatus->ssl_clientdn);
+			values[18] = BoolGetDatum(true);	/* ssl */
+			values[19] = CStringGetTextDatum(beentry->st_sslstatus->ssl_version);
+			values[20] = CStringGetTextDatum(beentry->st_sslstatus->ssl_cipher);
+			values[21] = Int32GetDatum(beentry->st_sslstatus->ssl_bits);
+			values[22] = BoolGetDatum(beentry->st_sslstatus->ssl_compression);
+			values[23] = CStringGetTextDatum(beentry->st_sslstatus->ssl_clientdn);
 		}
 		else
 		{
-			values[17] = BoolGetDatum(false);	/* ssl */
-			nulls[18] = nulls[19] = nulls[20] = nulls[21] = nulls[22] = true;
+			values[18] = BoolGetDatum(false);	/* ssl */
+			nulls[19] = nulls[20] = nulls[21] = nulls[22] = nulls[23] = true;
 		}
 
 		/* Values only available to role member */
@@ -690,10 +700,24 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 				wait_event = pgstat_get_wait_event(raw_wait_event);
 
 			}
-			else
+			else if (beentry->st_backendType != B_BACKEND)
 			{
-				wait_event_type = NULL;
-				wait_event = NULL;
+				/*
+				 * For an auxiliary process, retrieve process info from
+				 * AuxiliaryProcs stored in shared-memory.
+				 */
+				proc = AuxiliaryPidGetProc(beentry->st_procpid);
+
+				if (proc != NULL)
+				{
+					uint32		raw_wait_event;
+
+					raw_wait_event =
+						UINT32_ACCESS_ONCE(proc->wait_event_info);
+					wait_event_type =
+						pgstat_get_wait_event_type(raw_wait_event);
+					wait_event = pgstat_get_wait_event(raw_wait_event);
+				}
 			}
 
 			if (wait_event_type)
@@ -793,6 +817,9 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 					nulls[14] = true;
 				}
 			}
+			/* Add backend type */
+			values[17] =
+				CStringGetTextDatum(pgstat_get_backend_desc(beentry->st_backendType));
 		}
 		else
 		{
@@ -808,6 +835,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			nulls[12] = true;
 			nulls[13] = true;
 			nulls[14] = true;
+			nulls[17] = true;
 		}
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);