5 files changed, 52 insertions, 10 deletions
diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index cdaa32e29a4..911da776e80 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -87,6 +87,8 @@ typedef struct FixedParallelState
 	PGPROC	   *parallel_master_pgproc;
 	pid_t		parallel_master_pid;
 	BackendId	parallel_master_backend_id;
+	TimestampTz xact_ts;
+	TimestampTz stmt_ts;
 
 	/* Mutex protects remaining fields. */
 	slock_t		mutex;
@@ -318,6 +320,8 @@ InitializeParallelDSM(ParallelContext *pcxt)
 	fps->parallel_master_pgproc = MyProc;
 	fps->parallel_master_pid = MyProcPid;
 	fps->parallel_master_backend_id = MyBackendId;
+	fps->xact_ts = GetCurrentTransactionStartTimestamp();
+	fps->stmt_ts = GetCurrentStatementStartTimestamp();
 	SpinLockInit(&fps->mutex);
 	fps->last_xlog_end = 0;
 	shm_toc_insert(pcxt->toc, PARALLEL_KEY_FIXED, fps);
@@ -1312,6 +1316,13 @@ ParallelWorkerMain(Datum main_arg)
 		return;
 
 	/*
+	 * Restore transaction and statement start-time timestamps.  This must
+	 * happen before anything that would start a transaction, else asserts in
+	 * xact.c will fire.
+	 */
+	SetParallelStartTimestamps(fps->xact_ts, fps->stmt_ts);
+
+	/*
 	 * Identify the entry point to be called.  In theory this could result in
 	 * loading an additional library, though most likely the entry point is in
 	 * the core backend or in a library we just loaded.
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 875be180fe4..e3f668bf6ab 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -675,6 +675,22 @@ GetCurrentCommandId(bool used)
 }
 
 /*
+ *	SetParallelStartTimestamps
+ *
+ * In a parallel worker, we should inherit the parent transaction's
+ * timestamps rather than setting our own.  The parallel worker
+ * infrastructure must call this to provide those values before
+ * calling StartTransaction() or SetCurrentStatementStartTimestamp().
+ */
+void
+SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts)
+{
+	Assert(IsParallelWorker());
+	xactStartTimestamp = xact_ts;
+	stmtStartTimestamp = stmt_ts;
+}
+
+/*
  *	GetCurrentTransactionStartTimestamp
  */
 TimestampTz
@@ -708,11 +724,17 @@ GetCurrentTransactionStopTimestamp(void)
 
 /*
  *	SetCurrentStatementStartTimestamp
+ *
+ * In a parallel worker, this should already have been provided by a call
+ * to SetParallelStartTimestamps().
  */
 void
 SetCurrentStatementStartTimestamp(void)
 {
-	stmtStartTimestamp = GetCurrentTimestamp();
+	if (!IsParallelWorker())
+		stmtStartTimestamp = GetCurrentTimestamp();
+	else
+		Assert(stmtStartTimestamp != 0);
 }
 
 /*
@@ -1867,10 +1889,16 @@ StartTransaction(void)
 	/*
 	 * set transaction_timestamp() (a/k/a now()).  We want this to be the same
 	 * as the first command's statement_timestamp(), so don't do a fresh
-	 * GetCurrentTimestamp() call (which'd be expensive anyway).  Also, mark
-	 * xactStopTimestamp as unset.
+	 * GetCurrentTimestamp() call (which'd be expensive anyway).  In a
+	 * parallel worker, this should already have been provided by a call to
+	 * SetParallelStartTimestamps().
+	 *
+	 * Also, mark xactStopTimestamp as unset.
 	 */
-	xactStartTimestamp = stmtStartTimestamp;
+	if (!IsParallelWorker())
+		xactStartTimestamp = stmtStartTimestamp;
+	else
+		Assert(xactStartTimestamp != 0);
 	xactStopTimestamp = 0;
 	pgstat_report_xact_timestamp(xactStartTimestamp);
 
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 083e879d5c3..689c57c5926 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -359,6 +359,7 @@ extern SubTransactionId GetCurrentSubTransactionId(void);
 extern void MarkCurrentTransactionIdLoggedIfAny(void);
 extern bool SubTransactionIsActive(SubTransactionId subxid);
 extern CommandId GetCurrentCommandId(bool used);
+extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts);
 extern TimestampTz GetCurrentTransactionStartTimestamp(void);
 extern TimestampTz GetCurrentStatementStartTimestamp(void);
 extern TimestampTz GetCurrentTransactionStopTimestamp(void);
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 89e2b609165..1e38656fa7c 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201810051
+#define CATALOG_VERSION_NO	201810061
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 8579822bcd2..963ff6848a9 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -2073,7 +2073,8 @@
 { oid => '1365', descr => 'make ACL item',
   proname => 'makeaclitem', prorettype => 'aclitem',
   proargtypes => 'oid oid text bool', prosrc => 'makeaclitem' },
-{ oid => '3943', descr => 'show hardwired default privileges, primarily for use by the information schema',
+{ oid => '3943',
+  descr => 'show hardwired default privileges, primarily for use by the information schema',
   proname => 'acldefault', prorettype => '_aclitem', proargtypes => 'char oid',
   prosrc => 'acldefault_sql' },
 { oid => '1689',
@@ -2595,13 +2596,13 @@
   proname => 'timetzdate_pl', prolang => '14', prorettype => 'timestamptz',
   proargtypes => 'timetz date', prosrc => 'select ($2 + $1)' },
 { oid => '1299', descr => 'current transaction time',
-  proname => 'now', provolatile => 's', proparallel => 'r',
-  prorettype => 'timestamptz', proargtypes => '', prosrc => 'now' },
+  proname => 'now', provolatile => 's', prorettype => 'timestamptz',
+  proargtypes => '', prosrc => 'now' },
 { oid => '2647', descr => 'current transaction time',
   proname => 'transaction_timestamp', provolatile => 's',
   prorettype => 'timestamptz', proargtypes => '', prosrc => 'now' },
 { oid => '2648', descr => 'current statement time',
-  proname => 'statement_timestamp', provolatile => 's', proparallel => 'r',
+  proname => 'statement_timestamp', provolatile => 's',
   prorettype => 'timestamptz', proargtypes => '',
   prosrc => 'statement_timestamp' },
 { oid => '2649', descr => 'current clock time',
@@ -10208,7 +10209,8 @@
   proname => 'pg_ls_tmpdir', procost => '10', prorows => '20', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => 'oid',
   proallargtypes => '{oid,text,int8,timestamptz}', proargmodes => '{i,o,o,o}',
-  proargnames => '{tablespace,name,size,modification}', prosrc => 'pg_ls_tmpdir_1arg' },
+  proargnames => '{tablespace,name,size,modification}',
+  prosrc => 'pg_ls_tmpdir_1arg' },
 
 # hash partitioning constraint function
 { oid => '5028', descr => 'hash partition CHECK constraint',