3 files changed, 44 insertions, 4 deletions

diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index bf2fbd69982..1c5b4d067fc 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -71,6 +71,8 @@ typedef struct FixedParallelState
 	PGPROC	   *parallel_master_pgproc;
 	pid_t		parallel_master_pid;
 	BackendId	parallel_master_backend_id;
+	TimestampTz xact_ts;
+	TimestampTz stmt_ts;
 
 	/* Entrypoint for parallel workers. */
 	parallel_worker_main_type entrypoint;
@@ -282,6 +284,8 @@ 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();
 	fps->entrypoint = pcxt->entrypoint;
 	SpinLockInit(&fps->mutex);
 	fps->last_xlog_end = 0;
@@ -925,6 +929,13 @@ ParallelWorkerMain(Datum main_arg)
 	 */
 
 	/*
+	 * 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);
+
+	/*
 	 * Load libraries that were loaded by original backend.  We want to do
 	 * this before restoring GUCs, because the libraries might define custom
 	 * variables.
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index d3632c25cae..bda98e7924a 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -699,6 +699,22 @@ 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
@@ -732,11 +748,17 @@ 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);
 }
 
 /*
@@ -1875,10 +1897,16 @@ 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 b688ad952ad..e0010a4d965 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -313,6 +313,7 @@ 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);