diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3cdb1aff3c..f05140dd42 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3737,6 +3737,83 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
+
+
+ session_time double precision
+
+
+ Time spent by database sessions in this database, in milliseconds
+ (note that statistics are only updated when the state of a session
+ changes, so if sessions have been idle for a long time, this idle time
+ won't be included)
+
+
+
+
+
+ active_time double precision
+
+
+ Time spent executing SQL statements in this database, in milliseconds
+ (this corresponds to the states active and
+ fastpath function call in
+
+ pg_stat_activity)
+
+
+
+
+
+ idle_in_transaction_time double precision
+
+
+ Time spent idling while in a transaction in this database, in milliseconds
+ (this corresponds to the states idle in transaction and
+ idle in transaction (aborted) in
+
+ pg_stat_activity)
+
+
+
+
+
+ sessions bigint
+
+
+ Total number of sessions established to this database
+
+
+
+
+
+ sessions_abandoned bigint
+
+
+ Number of database sessions to this database that were terminated
+ because connection to the client was lost
+
+
+
+
+
+ sessions_fatal bigint
+
+
+ Number of database sessions to this database that were terminated
+ by fatal errors
+
+
+
+
+
+ sessions_killed bigint
+
+
+ Number of database sessions to this database that were terminated
+ by operator intervention
+
+
+
stats_reset timestamp with time zone
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 5d89e77dbe..fa58afd9d7 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -924,6 +924,13 @@ CREATE VIEW pg_stat_database AS
pg_stat_get_db_checksum_last_failure(D.oid) AS checksum_last_failure,
pg_stat_get_db_blk_read_time(D.oid) AS blk_read_time,
pg_stat_get_db_blk_write_time(D.oid) AS blk_write_time,
+ pg_stat_get_db_session_time(D.oid) AS session_time,
+ pg_stat_get_db_active_time(D.oid) AS active_time,
+ pg_stat_get_db_idle_in_transaction_time(D.oid) AS idle_in_transaction_time,
+ pg_stat_get_db_sessions(D.oid) AS sessions,
+ pg_stat_get_db_sessions_abandoned(D.oid) AS sessions_abandoned,
+ pg_stat_get_db_sessions_fatal(D.oid) AS sessions_fatal,
+ pg_stat_get_db_sessions_killed(D.oid) AS sessions_killed,
pg_stat_get_db_stat_reset_time(D.oid) AS stats_reset
FROM (
SELECT 0 AS oid, NULL::name AS datname
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 3f24a33ef1..f75b52719d 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -258,6 +258,9 @@ static int pgStatXactCommit = 0;
static int pgStatXactRollback = 0;
PgStat_Counter pgStatBlockReadTime = 0;
PgStat_Counter pgStatBlockWriteTime = 0;
+static PgStat_Counter pgStatActiveTime = 0;
+static PgStat_Counter pgStatTransactionIdleTime = 0;
+SessionEndType pgStatSessionEndCause = DISCONNECT_NORMAL;
/* Record that's written to 2PC state file when pgstat state is persisted */
typedef struct TwoPhasePgStatRecord
@@ -343,6 +346,7 @@ static void pgstat_send_tabstat(PgStat_MsgTabstat *tsmsg);
static void pgstat_send_funcstats(void);
static void pgstat_send_slru(void);
static HTAB *pgstat_collect_oids(Oid catalogid, AttrNumber anum_oid);
+static void pgstat_send_connstats(bool disconnect, TimestampTz last_report);
static PgStat_TableStatus *get_tabstat_entry(Oid rel_id, bool isshared);
@@ -378,6 +382,7 @@ static void pgstat_recv_funcpurge(PgStat_MsgFuncpurge *msg, int len);
static void pgstat_recv_recoveryconflict(PgStat_MsgRecoveryConflict *msg, int len);
static void pgstat_recv_deadlock(PgStat_MsgDeadlock *msg, int len);
static void pgstat_recv_checksum_failure(PgStat_MsgChecksumFailure *msg, int len);
+static void pgstat_recv_connstat(PgStat_MsgConn *msg, int len);
static void pgstat_recv_replslot(PgStat_MsgReplSlot *msg, int len);
static void pgstat_recv_tempfile(PgStat_MsgTempFile *msg, int len);
@@ -855,10 +860,14 @@ allow_immediate_pgstat_restart(void)
* per-table and function usage statistics to the collector. Note that this
* is called only when not within a transaction, so it is fair to use
* transaction stop time as an approximation of current time.
+ *
+ * "disconnect" is "true" only for the last call before the backend
+ * exits. This makes sure that no data is lost and that interrupted
+ * sessions are reported correctly.
* ----------
*/
void
-pgstat_report_stat(bool force)
+pgstat_report_stat(bool disconnect)
{
/* we assume this inits to all zeroes: */
static const PgStat_TableCounts all_zeroes;
@@ -873,17 +882,22 @@ pgstat_report_stat(bool force)
/* Don't expend a clock check if nothing to do */
if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) &&
pgStatXactCommit == 0 && pgStatXactRollback == 0 &&
- !have_function_stats)
+ !have_function_stats && !disconnect)
return;
/*
* Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL
- * msec since we last sent one, or the caller wants to force stats out.
+ * msec since we last sent one, or the backend is about to exit.
*/
now = GetCurrentTransactionStopTimestamp();
- if (!force &&
+ if (!disconnect &&
!TimestampDifferenceExceeds(last_report, now, PGSTAT_STAT_INTERVAL))
return;
+
+ /* for backends, send connection statistics */
+ if (MyBackendType == B_BACKEND)
+ pgstat_send_connstats(disconnect, last_report);
+
last_report = now;
/*
@@ -1351,6 +1365,48 @@ pgstat_drop_relation(Oid relid)
#endif /* NOT_USED */
+/* ----------
+ * pgstat_send_connstats() -
+ *
+ * Tell the collector about session statistics.
+ * The parameter "disconnect" will be true when the backend exits.
+ * "last_report" is the last time we were called (0 if never).
+ * ----------
+ */
+static void
+pgstat_send_connstats(bool disconnect, TimestampTz last_report)
+{
+ PgStat_MsgConn msg;
+ long secs;
+ int usecs;
+
+ if (pgStatSock == PGINVALID_SOCKET || !pgstat_track_counts)
+ return;
+
+ pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_CONNECTION);
+ msg.m_databaseid = MyDatabaseId;
+
+ /* session time since the last report */
+ TimestampDifference(((last_report == 0) ? MyStartTimestamp : last_report),
+ GetCurrentTimestamp(),
+ &secs, &usecs);
+ msg.m_session_time = secs * 1000000 + usecs;
+
+ msg.m_disconnect = disconnect ? pgStatSessionEndCause : DISCONNECT_NOT_YET;
+
+ msg.m_active_time = pgStatActiveTime;
+ pgStatActiveTime = 0;
+
+ msg.m_idle_in_xact_time = pgStatTransactionIdleTime;
+ pgStatTransactionIdleTime = 0;
+
+ /* report a new session only the first time */
+ msg.m_count = (last_report == 0) ? 1 : 0;
+
+ pgstat_send(&msg, sizeof(PgStat_MsgConn));
+}
+
+
/* ----------
* pgstat_reset_counters() -
*
@@ -3348,6 +3404,30 @@ pgstat_report_activity(BackendState state, const char *cmd_str)
}
current_timestamp = GetCurrentTimestamp();
+ /*
+ * If the state has changed from "active" or "idle in transaction",
+ * calculate the duration.
+ */
+ if ((beentry->st_state == STATE_RUNNING ||
+ beentry->st_state == STATE_FASTPATH ||
+ beentry->st_state == STATE_IDLEINTRANSACTION ||
+ beentry->st_state == STATE_IDLEINTRANSACTION_ABORTED) &&
+ state != beentry->st_state)
+ {
+ long secs;
+ int usecs;
+
+ TimestampDifference(beentry->st_state_start_timestamp,
+ current_timestamp,
+ &secs, &usecs);
+
+ if (beentry->st_state == STATE_RUNNING ||
+ beentry->st_state == STATE_FASTPATH)
+ pgStatActiveTime += secs * 1000000 + usecs;
+ else
+ pgStatTransactionIdleTime += secs * 1000000 + usecs;
+ }
+
/*
* Now update the status entry
*/
@@ -4919,6 +4999,10 @@ PgstatCollectorMain(int argc, char *argv[])
pgstat_recv_replslot(&msg.msg_replslot, len);
break;
+ case PGSTAT_MTYPE_CONNECTION:
+ pgstat_recv_connstat(&msg.msg_conn, len);
+ break;
+
default:
break;
}
@@ -4993,6 +5077,13 @@ reset_dbentry_counters(PgStat_StatDBEntry *dbentry)
dbentry->last_checksum_failure = 0;
dbentry->n_block_read_time = 0;
dbentry->n_block_write_time = 0;
+ dbentry->n_sessions = 0;
+ dbentry->total_session_time = 0;
+ dbentry->total_active_time = 0;
+ dbentry->total_idle_in_xact_time = 0;
+ dbentry->n_sessions_abandoned = 0;
+ dbentry->n_sessions_fatal = 0;
+ dbentry->n_sessions_killed = 0;
dbentry->stat_reset_timestamp = GetCurrentTimestamp();
dbentry->stats_timestamp = 0;
@@ -6944,6 +7035,41 @@ pgstat_recv_replslot(PgStat_MsgReplSlot *msg, int len)
}
}
+/* ----------
+ * pgstat_recv_connstat() -
+ *
+ * Process connection information.
+ * ----------
+ */
+static void
+pgstat_recv_connstat(PgStat_MsgConn *msg, int len)
+{
+ PgStat_StatDBEntry *dbentry;
+
+ dbentry = pgstat_get_db_entry(msg->m_databaseid, true);
+
+ dbentry->n_sessions += msg->m_count;
+ dbentry->total_session_time += msg->m_session_time;
+ dbentry->total_active_time += msg->m_active_time;
+ dbentry->total_idle_in_xact_time += msg->m_idle_in_xact_time;
+ switch (msg->m_disconnect)
+ {
+ case DISCONNECT_NOT_YET:
+ case DISCONNECT_NORMAL:
+ /* we don't collect these */
+ break;
+ case DISCONNECT_CLIENT_EOF:
+ dbentry->n_sessions_abandoned++;
+ break;
+ case DISCONNECT_FATAL:
+ dbentry->n_sessions_fatal++;
+ break;
+ case DISCONNECT_KILLED:
+ dbentry->n_sessions_killed++;
+ break;
+ }
+}
+
/* ----------
* pgstat_recv_tempfile() -
*
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 28055680aa..8dab9fd578 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2865,6 +2865,9 @@ die(SIGNAL_ARGS)
ProcDiePending = true;
}
+ /* for the statistics collector */
+ pgStatSessionEndCause = DISCONNECT_KILLED;
+
/* If we're still here, waken anything waiting on the process latch */
SetLatch(MyLatch);
@@ -4579,9 +4582,15 @@ PostgresMain(int argc, char *argv[],
* means unexpected loss of frontend connection. Either way,
* perform normal shutdown.
*/
- case 'X':
case EOF:
+ /* for the statistics collector */
+ pgStatSessionEndCause = DISCONNECT_CLIENT_EOF;
+
+ /* FALLTHROUGH */
+
+ case 'X':
+
/*
* Reset whereToSendOutput to prevent ereport from attempting
* to send any more messages to client.
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 5c12a165a1..62bff52638 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1631,6 +1631,100 @@ pg_stat_get_db_blk_write_time(PG_FUNCTION_ARGS)
PG_RETURN_FLOAT8(result);
}
+Datum
+pg_stat_get_db_session_time(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ double result = 0.0;
+ PgStat_StatDBEntry *dbentry;
+
+ /* convert counter from microsec to millisec for display */
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = ((double) dbentry->total_session_time) / 1000.0;
+
+ PG_RETURN_FLOAT8(result);
+}
+
+Datum
+pg_stat_get_db_active_time(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ double result = 0.0;
+ PgStat_StatDBEntry *dbentry;
+
+ /* convert counter from microsec to millisec for display */
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = ((double) dbentry->total_active_time) / 1000.0;
+
+ PG_RETURN_FLOAT8(result);
+}
+
+Datum
+pg_stat_get_db_idle_in_transaction_time(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ double result = 0.0;
+ PgStat_StatDBEntry *dbentry;
+
+ /* convert counter from microsec to millisec for display */
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = ((double) dbentry->total_idle_in_xact_time) / 1000.0;
+
+ PG_RETURN_FLOAT8(result);
+}
+
+Datum
+pg_stat_get_db_sessions(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ int64 result = 0;
+ PgStat_StatDBEntry *dbentry;
+
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = (int64) (dbentry->n_sessions);
+
+ PG_RETURN_INT64(result);
+}
+
+Datum
+pg_stat_get_db_sessions_abandoned(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ int64 result = 0;
+ PgStat_StatDBEntry *dbentry;
+
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = (int64) (dbentry->n_sessions_abandoned);
+
+ PG_RETURN_INT64(result);
+}
+
+Datum
+pg_stat_get_db_sessions_fatal(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ int64 result = 0;
+ PgStat_StatDBEntry *dbentry;
+
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = (int64) (dbentry->n_sessions_fatal);
+
+ PG_RETURN_INT64(result);
+}
+
+Datum
+pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS)
+{
+ Oid dbid = PG_GETARG_OID(0);
+ int64 result = 0;
+ PgStat_StatDBEntry *dbentry;
+
+ if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) != NULL)
+ result = (int64) (dbentry->n_sessions_killed);
+
+ PG_RETURN_INT64(result);
+}
+
Datum
pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
{
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 7790f6ab25..80c2672461 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -72,6 +72,7 @@
#include "libpq/pqformat.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "postmaster/bgworker.h"
#include "postmaster/postmaster.h"
#include "postmaster/syslogger.h"
@@ -656,6 +657,13 @@ errfinish(const char *filename, int lineno, const char *funcname)
fflush(stdout);
fflush(stderr);
+ /*
+ * Let the statistics collector know. Only mark the session as
+ * terminated by fatal error if there is no other known cause.
+ */
+ if (pgStatSessionEndCause == DISCONNECT_NORMAL)
+ pgStatSessionEndCause = DISCONNECT_FATAL;
+
/*
* Do normal process-exit cleanup, then return exit code 1 to indicate
* FATAL termination. The postmaster may or may not consider this
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 747135dab4..385d108c29 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 202101131
+#define CATALOG_VERSION_NO 202101171
#endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index d27336adcd..dd64c3bd60 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5440,6 +5440,38 @@
proname => 'pg_stat_get_db_blk_write_time', provolatile => 's',
proparallel => 'r', prorettype => 'float8', proargtypes => 'oid',
prosrc => 'pg_stat_get_db_blk_write_time' },
+{ oid => '9575', descr => 'statistics: session time, in milliseconds',
+ proname => 'pg_stat_get_db_session_time', provolatile => 's',
+ proparallel => 'r', prorettype => 'float8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_session_time' },
+{ oid => '9576', descr => 'statistics: session active time, in milliseconds',
+ proname => 'pg_stat_get_db_active_time', provolatile => 's',
+ proparallel => 'r', prorettype => 'float8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_active_time' },
+{ oid => '9577',
+ descr => 'statistics: session idle in transaction time, in milliseconds',
+ proname => 'pg_stat_get_db_idle_in_transaction_time', provolatile => 's',
+ proparallel => 'r', prorettype => 'float8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_idle_in_transaction_time' },
+{ oid => '9578', descr => 'statistics: total number of sessions',
+ proname => 'pg_stat_get_db_sessions', provolatile => 's', proparallel => 'r',
+ prorettype => 'int8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_sessions' },
+{ oid => '9579',
+ descr => 'statistics: number of sessions disconnected by the client closing the network connection',
+ proname => 'pg_stat_get_db_sessions_abandoned', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_sessions_abandoned' },
+{ oid => '9580',
+ descr => 'statistics: number of sessions disconnected by fatal errors',
+ proname => 'pg_stat_get_db_sessions_fatal', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_sessions_fatal' },
+{ oid => '9581',
+ descr => 'statistics: number of sessions killed by administrative action',
+ proname => 'pg_stat_get_db_sessions_killed', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
+ prosrc => 'pg_stat_get_db_sessions_killed' },
{ oid => '3195', descr => 'statistics: information about WAL archiver',
proname => 'pg_stat_get_archiver', proisstrict => 'f', provolatile => 's',
proparallel => 'r', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index c38b689710..a384f6eb56 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -41,6 +41,16 @@ typedef enum TrackFunctionsLevel
TRACK_FUNC_ALL
} TrackFunctionsLevel;
+/* Values to track the cause of session termination */
+typedef enum SessionEndType
+{
+ DISCONNECT_NOT_YET, /* still active */
+ DISCONNECT_NORMAL,
+ DISCONNECT_CLIENT_EOF,
+ DISCONNECT_FATAL,
+ DISCONNECT_KILLED
+} SessionEndType;
+
/* ----------
* The types of backend -> collector messages
* ----------
@@ -71,6 +81,7 @@ typedef enum StatMsgType
PGSTAT_MTYPE_DEADLOCK,
PGSTAT_MTYPE_CHECKSUMFAILURE,
PGSTAT_MTYPE_REPLSLOT,
+ PGSTAT_MTYPE_CONNECTION,
} StatMsgType;
/* ----------
@@ -622,6 +633,21 @@ typedef struct PgStat_MsgChecksumFailure
TimestampTz m_failure_time;
} PgStat_MsgChecksumFailure;
+/* ----------
+ * PgStat_MsgConn Sent by the backend to update connection statistics.
+ * ----------
+ */
+typedef struct PgStat_MsgConn
+{
+ PgStat_MsgHdr m_hdr;
+ Oid m_databaseid;
+ PgStat_Counter m_count;
+ PgStat_Counter m_session_time;
+ PgStat_Counter m_active_time;
+ PgStat_Counter m_idle_in_xact_time;
+ SessionEndType m_disconnect;
+} PgStat_MsgConn;
+
/* ----------
* PgStat_Msg Union over all possible messages.
@@ -654,6 +680,7 @@ typedef union PgStat_Msg
PgStat_MsgTempFile msg_tempfile;
PgStat_MsgChecksumFailure msg_checksumfailure;
PgStat_MsgReplSlot msg_replslot;
+ PgStat_MsgConn msg_conn;
} PgStat_Msg;
@@ -696,6 +723,13 @@ typedef struct PgStat_StatDBEntry
TimestampTz last_checksum_failure;
PgStat_Counter n_block_read_time; /* times in microseconds */
PgStat_Counter n_block_write_time;
+ PgStat_Counter n_sessions;
+ PgStat_Counter total_session_time;
+ PgStat_Counter total_active_time;
+ PgStat_Counter total_idle_in_xact_time;
+ PgStat_Counter n_sessions_abandoned;
+ PgStat_Counter n_sessions_fatal;
+ PgStat_Counter n_sessions_killed;
TimestampTz stat_reset_timestamp;
TimestampTz stats_timestamp; /* time of db stats file update */
@@ -1354,6 +1388,11 @@ extern PgStat_MsgWal WalStats;
extern PgStat_Counter pgStatBlockReadTime;
extern PgStat_Counter pgStatBlockWriteTime;
+/*
+ * Updated by the traffic cop and in errfinish()
+ */
+extern SessionEndType pgStatSessionEndCause;
+
/* ----------
* Functions called from postmaster
* ----------
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index a687e99d1e..6173473de9 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1848,6 +1848,13 @@ pg_stat_database| SELECT d.oid AS datid,
pg_stat_get_db_checksum_last_failure(d.oid) AS checksum_last_failure,
pg_stat_get_db_blk_read_time(d.oid) AS blk_read_time,
pg_stat_get_db_blk_write_time(d.oid) AS blk_write_time,
+ pg_stat_get_db_session_time(d.oid) AS session_time,
+ pg_stat_get_db_active_time(d.oid) AS active_time,
+ pg_stat_get_db_idle_in_transaction_time(d.oid) AS idle_in_transaction_time,
+ pg_stat_get_db_sessions(d.oid) AS sessions,
+ pg_stat_get_db_sessions_abandoned(d.oid) AS sessions_abandoned,
+ pg_stat_get_db_sessions_fatal(d.oid) AS sessions_fatal,
+ pg_stat_get_db_sessions_killed(d.oid) AS sessions_killed,
pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset
FROM ( SELECT 0 AS oid,
NULL::name AS datname