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初始化节点时每个节点的estate指向一样的东西吗？

• 其实肯定一样的
• 因为初始化节点的最外层是被这个函数包裹着

PlanState *ExecInitNode(Plan *node, EState *estate, int eflags){

• 那这个estate到底起到什么作用呢？
• 例如在ExecInitNestLoop中
  • 这个estate会在

- ExecAssignExprContext(estate, &nlstate->js.ps);  - ExecInitResultTupleSlotTL(estate, &nlstate->js.ps);  - ExecInitNullTupleSlot(estate,									  ExecGetResultType(innerPlanState(nlstate)));

• 上面三个地方用到。

• 下面这个函数似乎给出了estate的作用哦！

• 有点想要在estate->es_tupleTable这个list上面加一点TupleTableSlots

  • 然后把这个槽赋给planstate->ps_ResultTupleSlot

• 有意思的是他的第一个参数不就是list **吗！！

/* ---------------- *		ExecInitResultTupleSlotTL * *		Initialize result tuple slot, using the plan node's targetlist. * ---------------- */voidExecInitResultTupleSlotTL(EState *estate, PlanState *planstate){
   	bool		hasoid;	TupleDesc	tupDesc;	if (ExecContextForcesOids(planstate, &hasoid))	{
   		/* context forces OID choice; hasoid is now set correctly */	}	else	{
   		/* given free choice, don't leave space for OIDs in result tuples */		hasoid = false;	}	tupDesc = ExecTypeFromTL(planstate->plan->targetlist, hasoid);	planstate->ps_ResultTupleSlot = ExecAllocTableSlot(&estate->es_tupleTable, tupDesc);}

• ExecInitScanTupleSlot更是直接的展示了
  • 我认识的一个真理
  • 每一个节点的容器都是放在estate->es_tupleTable中的啊！

/* ---------------- *		ExecInitScanTupleSlot * ---------------- */voidExecInitScanTupleSlot(EState *estate, ScanState *scanstate, TupleDesc tupledesc){
   	scanstate->ss_ScanTupleSlot = ExecAllocTableSlot(&estate->es_tupleTable,													 tupledesc);	scanstate->ps.scandesc = tupledesc;}/* -------------------------------- *		ExecAllocTableSlot * *		Create a tuple table slot within a tuple table (which is just a List). * -------------------------------- */TupleTableSlot *ExecAllocTableSlot(List **tupleTable, TupleDesc desc){
   	TupleTableSlot *slot = MakeTupleTableSlot(desc);	*tupleTable = lappend(*tupleTable, slot);	return slot;}

MakeTupleTableSlot

/* -------------------------------- *		MakeTupleTableSlot * *		Basic routine to make an empty TupleTableSlot. If tupleDesc is *		specified the slot's descriptor is fixed for it's lifetime, gaining *		some efficiency. If that's undesirable, pass NULL. * -------------------------------- */TupleTableSlot *MakeTupleTableSlot(TupleDesc tupleDesc){
   	Size		sz;	TupleTableSlot *slot;	/*	 * When a fixed descriptor is specified, we can reduce overhead by	 * allocating the entire slot in one go.	 */	if (tupleDesc)		sz = MAXALIGN(sizeof(TupleTableSlot)) +			MAXALIGN(tupleDesc->natts * sizeof(Datum)) +			MAXALIGN(tupleDesc->natts * sizeof(bool));	else		sz = sizeof(TupleTableSlot);	slot = palloc0(sz);	slot->type = T_TupleTableSlot;	slot->tts_isempty = true;	slot->tts_shouldFree = false;	slot->tts_shouldFreeMin = false;	slot->tts_tuple = NULL;	slot->tts_fixedTupleDescriptor = tupleDesc != NULL;	slot->tts_tupleDescriptor = tupleDesc;	slot->tts_mcxt = CurrentMemoryContext;	slot->tts_buffer = InvalidBuffer;	slot->tts_nvalid = 0;	slot->tts_values = NULL;	slot->tts_isnull = NULL;	slot->tts_mintuple = NULL;	if (tupleDesc != NULL)	{
   		slot->tts_values = (Datum *)			(((char *) slot)			 + MAXALIGN(sizeof(TupleTableSlot)));		slot->tts_isnull = (bool *)			(((char *) slot)			 + MAXALIGN(sizeof(TupleTableSlot))			 + MAXALIGN(tupleDesc->natts * sizeof(Datum)));		PinTupleDesc(tupleDesc);	}	return slot;}

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