execmain.c

关系型数据库 Postgresql 6.5.2

			Datum		datum;
			HeapTuple	newTuple;
			bool		isNull;

			/*
			 * extract the 'ctid' junk attribute.
			 */
			if (operation == CMD_UPDATE || operation == CMD_DELETE)
			{
				if (!ExecGetJunkAttribute(junkfilter,
										  slot,
										  "ctid",
										  &datum,
										  &isNull))
					elog(ERROR, "ExecutePlan: NO (junk) `ctid' was found!");

				if (isNull)
					elog(ERROR, "ExecutePlan: (junk) `ctid' is NULL!");

				tupleid = (ItemPointer) DatumGetPointer(datum);
				tuple_ctid = *tupleid;	/* make sure we don't free the
										 * ctid!! */
				tupleid = &tuple_ctid;
			}
			else if (estate->es_rowMark != NULL)
			{
				List	   *l;
				execRowMark *erm;
				Buffer		buffer;
				HeapTupleData tuple;
				TupleTableSlot *newSlot;
				int			test;

		lmark:	;
				foreach(l, estate->es_rowMark)
				{
					erm = lfirst(l);
					if (!ExecGetJunkAttribute(junkfilter,
											  slot,
											  erm->resname,
											  &datum,
											  &isNull))
						elog(ERROR, "ExecutePlan: NO (junk) `%s' was found!", erm->resname);

					if (isNull)
						elog(ERROR, "ExecutePlan: (junk) `%s' is NULL!", erm->resname);

					tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
					test = heap_mark4update(erm->relation, &tuple, &buffer);
					ReleaseBuffer(buffer);
					switch (test)
					{
						case HeapTupleSelfUpdated:
						case HeapTupleMayBeUpdated:
							break;

						case HeapTupleUpdated:
							if (XactIsoLevel == XACT_SERIALIZABLE)
							{
								elog(ERROR, "Can't serialize access due to concurrent update");
								return (NULL);
							}
							else if (!(ItemPointerEquals(&(tuple.t_self),
								  (ItemPointer) DatumGetPointer(datum))))
							{
								newSlot = EvalPlanQual(estate, erm->rti, &(tuple.t_self));
								if (!(TupIsNull(newSlot)))
								{
									slot = newSlot;
									estate->es_useEvalPlan = true;
									goto lmark;
								}
							}

							/*
							 * if tuple was deleted or PlanQual failed for
							 * updated tuple - we have not return this
							 * tuple!
							 */
							goto lnext;

						default:
							elog(ERROR, "Unknown status %u from heap_mark4update", test);
							return (NULL);
					}
				}
			}

			/*
			 * Finally create a new "clean" tuple with all junk attributes
			 * removed
			 */
			newTuple = ExecRemoveJunk(junkfilter, slot);

			slot = ExecStoreTuple(newTuple,		/* tuple to store */
								  slot, /* destination slot */
								  InvalidBuffer,		/* this tuple has no
														 * buffer */
								  true);		/* tuple should be pfreed */
		}						/* if (junkfilter... */

		/*
		 * now that we have a tuple, do the appropriate thing with it..
		 * either return it to the user, add it to a relation someplace,
		 * delete it from a relation, or modify some of it's attributes.
		 */

		switch (operation)
		{
			case CMD_SELECT:
				ExecRetrieve(slot,		/* slot containing tuple */
							 destfunc,	/* destination's tuple-receiver
										 * obj */
							 estate);	/* */
				result = slot;
				break;

			case CMD_INSERT:
				ExecAppend(slot, tupleid, estate);
				result = NULL;
				break;

			case CMD_DELETE:
				ExecDelete(slot, tupleid, estate);
				result = NULL;
				break;

			case CMD_UPDATE:
				ExecReplace(slot, tupleid, estate);
				result = NULL;
				break;

			default:
				elog(DEBUG, "ExecutePlan: unknown operation in queryDesc");
				result = NULL;
				break;
		}

		/*
		 * check our tuple count.. if we've returned the proper number
		 * then return, else loop again and process more tuples..
		 */
		current_tuple_count += 1;
		if (numberTuples == current_tuple_count)
			break;
	}

	/*
	 * here, result is either a slot containing a tuple in the case of a
	 * RETRIEVE or NULL otherwise.
	 */
	return result;
}

/* ----------------------------------------------------------------
 *		ExecRetrieve
 *
 *		RETRIEVEs are easy.. we just pass the tuple to the appropriate
 *		print function.  The only complexity is when we do a
 *		"retrieve into", in which case we insert the tuple into
 *		the appropriate relation (note: this is a newly created relation
 *		so we don't need to worry about indices or locks.)
 * ----------------------------------------------------------------
 */
static void
ExecRetrieve(TupleTableSlot *slot,
			 DestReceiver *destfunc,
			 EState *estate)
{
	HeapTuple	tuple;
	TupleDesc	attrtype;

	/*
	 * get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;
	attrtype = slot->ttc_tupleDescriptor;

	/*
	 * insert the tuple into the "into relation"
	 */
	if (estate->es_into_relation_descriptor != NULL)
	{
		heap_insert(estate->es_into_relation_descriptor, tuple);
		IncrAppended();
	}

	/*
	 * send the tuple to the front end (or the screen)
	 */
	(*destfunc->receiveTuple) (tuple, attrtype, destfunc);
	IncrRetrieved();
	(estate->es_processed)++;
}

/* ----------------------------------------------------------------
 *		ExecAppend
 *
 *		APPENDs are trickier.. we have to insert the tuple into
 *		the base relation and insert appropriate tuples into the
 *		index relations.
 * ----------------------------------------------------------------
 */

static void
ExecAppend(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	HeapTuple	tuple;
	RelationInfo *resultRelationInfo;
	Relation	resultRelationDesc;
	int			numIndices;
	Oid			newId;

	/*
	 * get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;

	/*
	 * get information on the result relation
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/*
	 * have to add code to preform unique checking here. cim -12/1/89
	 */

	/* BEFORE ROW INSERT Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_INSERT] > 0)
	{
		HeapTuple	newtuple;

		newtuple = ExecBRInsertTriggers(resultRelationDesc, tuple);

		if (newtuple == NULL)	/* "do nothing" */
			return;

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			Assert(slot->ttc_shouldFree);
			pfree(tuple);
			slot->val = tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of a tuple
	 */

	if (resultRelationDesc->rd_att->constr)
		ExecConstraints("ExecAppend", resultRelationDesc, tuple, estate);

	/*
	 * insert the tuple
	 */
	newId = heap_insert(resultRelationDesc,		/* relation desc */
						tuple); /* heap tuple */
	IncrAppended();

	/*
	 * process indices
	 *
	 * Note: heap_insert adds a new tuple to a relation.  As a side effect,
	 * the tupleid of the new tuple is placed in the new tuple's t_ctid
	 * field.
	 */
	numIndices = resultRelationInfo->ri_NumIndices;
	if (numIndices > 0)
		ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);
	(estate->es_processed)++;
	estate->es_lastoid = newId;

	/* AFTER ROW INSERT Triggers */
	if (resultRelationDesc->trigdesc &&
	 resultRelationDesc->trigdesc->n_after_row[TRIGGER_EVENT_INSERT] > 0)
		ExecARInsertTriggers(resultRelationDesc, tuple);
}

/* ----------------------------------------------------------------
 *		ExecDelete
 *
 *		DELETE is like append, we delete the tuple and its
 *		index tuples.
 * ----------------------------------------------------------------
 */
static void
ExecDelete(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	RelationInfo *resultRelationInfo;
	Relation	resultRelationDesc;
	ItemPointerData ctid;
	int			result;

	/*
	 * get the result relation information
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/* BEFORE ROW DELETE Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_DELETE] > 0)
	{
		bool		dodelete;

		dodelete = ExecBRDeleteTriggers(estate, tupleid);

		if (!dodelete)			/* "do nothing" */
			return;
	}

	/*
	 * delete the tuple
	 */
ldelete:;
	result = heap_delete(resultRelationDesc, tupleid, &ctid);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				elog(ERROR, "Can't serialize access due to concurrent update");
			else if (!(ItemPointerEquals(tupleid, &ctid)))
			{
				TupleTableSlot *epqslot = EvalPlanQual(estate,
						  resultRelationInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					goto ldelete;
				}
			}
			return;

		default:
			elog(ERROR, "Unknown status %u from heap_delete", result);
			return;
	}

	IncrDeleted();
	(estate->es_processed)++;

	/*
	 * Note: Normally one would think that we have to delete index tuples
	 * associated with the heap tuple now..
	 *
	 * ... but in POSTGRES, we have no need to do this because the vacuum
	 * daemon automatically opens an index scan and deletes index tuples
	 * when it finds deleted heap tuples. -cim 9/27/89
	 */

	/* AFTER ROW DELETE Triggers */
	if (resultRelationDesc->trigdesc &&
	 resultRelationDesc->trigdesc->n_after_row[TRIGGER_EVENT_DELETE] > 0)
		ExecARDeleteTriggers(estate, tupleid);

}

/* ----------------------------------------------------------------
 *		ExecReplace
 *
 *		note: we can't run replace queries with transactions
 *		off because replaces are actually appends and our
 *		scan will mistakenly loop forever, replacing the tuple
 *		it just appended..	This should be fixed but until it
 *		is, we don't want to get stuck in an infinite loop
 *		which corrupts your database..
 * ----------------------------------------------------------------
 */
static void
ExecReplace(TupleTableSlot *slot,
			ItemPointer tupleid,
			EState *estate)
{
	HeapTuple	tuple;
	RelationInfo *resultRelationInfo;
	Relation	resultRelationDesc;
	ItemPointerData ctid;
	int			result;
	int			numIndices;

	/*
	 * abort the operation if not running transactions
	 */
	if (IsBootstrapProcessingMode())
	{
		elog(DEBUG, "ExecReplace: replace can't run without transactions");
		return;
	}

	/*
	 * get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;

	/*
	 * get the result relation information
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/*
	 * have to add code to preform unique checking here. in the event of
	 * unique tuples, this becomes a deletion of the original tuple
	 * affected by the replace. cim -12/1/89
	 */

	/* BEFORE ROW UPDATE Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_UPDATE] > 0)
	{
		HeapTuple	newtuple;

		newtuple = ExecBRUpdateTriggers(estate, tupleid, tuple);

		if (newtuple == NULL)	/* "do nothing" */
			return;

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			Assert(slot->ttc_shouldFree);
			pfree(tuple);
			slot->val = tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of a tuple
	 */

	if (resultRelationDesc->rd_att->constr)
		ExecConstraints("ExecReplace", resultRelationDesc, tuple, estate);

	/*
	 * replace the heap tuple
	 */
lreplace:;
	result = heap_replace(resultRelationDesc, tupleid, tuple, &ctid);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				elog(ERROR, "Can't serialize access due to concurrent update");
			else if (!(ItemPointerEquals(tupleid, &ctid)))
			{
				TupleTableSlot *epqslot = EvalPlanQual(estate,
						  resultRelationInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					tuple = ExecRemoveJunk(estate->es_junkFilter, epqslot);