本节介绍ExecutePlan函数

相关数据结构

typedef enum ScanDirection
{
	BackwardScanDirection = -1,
	NoMovementScanDirection = 0,
	ForwardScanDirection = 1
} ScanDirection;

ExecutePlan函数

static void
ExecutePlan(EState *estate,
			PlanState *planstate,
			bool use_parallel_mode,
			CmdType operation,
			bool sendTuples,
			uint64 numberTuples,
			ScanDirection direction,
			DestReceiver *dest,
			bool execute_once);

执行查询计划，直到获取到numberTuples个元组，并且处理时朝direction方向移动。

//class="lazy" data-src/backend/executor/execMain.c


current_tuple_count = 0;


estate->es_direction = direction;


if (!execute_once)
	use_parallel_mode = false;

estate->es_use_parallel_mode = use_parallel_mode;
if (use_parallel_mode)
	EnterParallelMode();


for (;;)
{
	
	ResetPerTupleExprContext(estate);
	
	
	slot = ExecProcNode(planstate);
	
	
	if (TupIsNull(slot))
	{
		
		if (!(estate->es_top_eflags & EXEC_FLAG_BACKWARD))
			(void) ExecShutdownNode(planstate);
		break;
	}
	
	
	if (estate->es_junkFilter != NULL)
		slot = ExecFilterJunk(estate->es_junkFilter, slot);
	
	
	if (sendTuples)
	{
		
		if (!dest->receiveSlot(slot, dest))
			break;
	}
	
	
	if (operation == CMD_SELECT)
		(estate->es_processed)++;
	
	
	current_tuple_count++;
	if (numberTuples && numberTuples == current_tuple_count)
	{
		
		if (!(estate->es_top_eflags & EXEC_FLAG_BACKWARD))
			(void) ExecShutdownNode(planstate);
		break;
	}
}

if (use_parallel_mode)
	ExitParallelMode();