2 files changed, 43 insertions, 4 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);