Function AssignGangs

src/backend/executor/execUtils.c:1823–1840

* Function AssignGangs runs on the QD and finishes construction of the * global slice table for a plan by assigning gangs allocated by the * executor factory to the slices of the slice table. * * On entry, the executor slice table (at queryDesc->estate->es_sliceTable) * has been initialized and has correct (by InitSliceTable function) * * Gang assignment involves taking an inventory of the

 * slice in the slice table.
 */
void
AssignGangs(CdbDispatcherState *ds, QueryDesc *queryDesc)
{
	SliceTable	*sliceTable;
	EState		*estate;
	int			rootIdx;

	estate = queryDesc->estate;
	sliceTable = estate->es_sliceTable;
	rootIdx = RootSliceIndex(queryDesc->estate);

	/* cleanup processMap because initPlan and main Plan share the same slice table */
	for (int i = 0; i < sliceTable->numSlices; i++)
		sliceTable->slices[i].processesMap = NULL;

	AssignWriterGangFirst(ds, sliceTable, rootIdx);
	InventorySliceTree(ds, sliceTable, rootIdx);
}

/*
 * AssignWriterGangFirst() - Try to assign writer gang first.