Function ExecParallelReinitialize

src/backend/executor/execParallel.c:900–944

* Re-initialize the parallel executor shared memory state before launching * a fresh batch of workers. */

 * a fresh batch of workers.
 */
void
ExecParallelReinitialize(PlanState *planstate,
						 ParallelExecutorInfo *pei,
						 Bitmapset *sendParams)
{
	EState	   *estate = planstate->state;
	FixedParallelExecutorState *fpes;

	/* Old workers must already be shut down */
	Assert(pei->finished);

	/*
	 * Force any initplan outputs that we're going to pass to workers to be
	 * evaluated, if they weren't already (see comments in
	 * ExecInitParallelPlan).
	 */
	ExecSetParamPlanMulti(sendParams, GetPerTupleExprContext(estate), NULL);

	ReinitializeParallelDSM(pei->pcxt);
	pei->tqueue = ExecParallelSetupTupleQueues(pei->pcxt, true);
	pei->reader = NULL;
	pei->finished = false;

	fpes = shm_toc_lookup(pei->pcxt->toc, PARALLEL_KEY_EXECUTOR_FIXED, false);

	/* Free any serialized parameters from the last round. */
	if (DsaPointerIsValid(fpes->param_exec))
	{
		dsa_free(pei->area, fpes->param_exec);
		fpes->param_exec = InvalidDsaPointer;
	}

	/* Serialize current parameter values if required. */
	if (!bms_is_empty(sendParams))
	{
		pei->param_exec = SerializeParamExecParams(estate, sendParams,
												   pei->area);
		fpes->param_exec = pei->param_exec;
	}

	/* Traverse plan tree and let each child node reset associated state. */
	estate->es_query_dsa = pei->area;
	ExecParallelReInitializeDSM(planstate, pei->pcxt);
	estate->es_query_dsa = NULL;
}

/*
 * Traverse plan tree to reinitialize per-node dynamic shared memory state