execmain.c

PostgreSQL7.4.6 for Linux

		/* Reset the per-output-tuple exprcontext */
		ResetPerTupleExprContext(estate);

		/*
		 * Execute the plan and obtain a tuple
		 */
lnext:	;
		if (estate->es_useEvalPlan)
		{
			slot = EvalPlanQualNext(estate);
			if (TupIsNull(slot))
				slot = ExecProcNode(planstate);
		}
		else
			slot = ExecProcNode(planstate);

		/*
		 * if the tuple is null, then we assume there is nothing more to
		 * process so we just return null...
		 */
		if (TupIsNull(slot))
		{
			result = NULL;
			break;
		}

		/*
		 * if we have a junk filter, then project a new tuple with the
		 * junk removed.
		 *
		 * Store this new "clean" tuple in the junkfilter's resultSlot.
		 * (Formerly, we stored it back over the "dirty" tuple, which is
		 * WRONG because that tuple slot has the wrong descriptor.)
		 *
		 * Also, extract all the junk information we need.
		 */
		if ((junkfilter = estate->es_junkFilter) != (JunkFilter *) NULL)
		{
			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, "could not find junk ctid column");

				/* shouldn't ever get a null result... */
				if (isNull)
					elog(ERROR, "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 != NIL)
			{
				List	   *l;

		lmark:	;
				foreach(l, estate->es_rowMark)
				{
					execRowMark *erm = lfirst(l);
					Buffer		buffer;
					HeapTupleData tuple;
					TupleTableSlot *newSlot;
					int			test;

					if (!ExecGetJunkAttribute(junkfilter,
											  slot,
											  erm->resname,
											  &datum,
											  &isNull))
						elog(ERROR, "could not find junk \"%s\" column",
							 erm->resname);

					/* shouldn't ever get a null result... */
					if (isNull)
						elog(ERROR, "\"%s\" is NULL", erm->resname);

					tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
					test = heap_mark4update(erm->relation, &tuple, &buffer,
											estate->es_snapshot->curcid);
					ReleaseBuffer(buffer);
					switch (test)
					{
						case HeapTupleSelfUpdated:
							/* treat it as deleted; do not process */
							goto lnext;

						case HeapTupleMayBeUpdated:
							break;

						case HeapTupleUpdated:
							if (XactIsoLevel == XACT_SERIALIZABLE)
								ereport(ERROR,
										(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
										 errmsg("could not serialize access due to concurrent update")));
							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 must not return this
							 * tuple!
							 */
							goto lnext;

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

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

			slot = ExecStoreTuple(newTuple,		/* tuple to store */
								  junkfilter->jf_resultSlot,	/* dest slot */
								  InvalidBuffer,		/* this tuple has no
														 * buffer */
								  true);		/* tuple should be pfreed */
		}

		/*
		 * 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 its attributes.
		 */
		switch (operation)
		{
			case CMD_SELECT:
				ExecSelect(slot,	/* slot containing tuple */
						   dest,	/* destination's tuple-receiver obj */
						   estate);
				result = slot;
				break;

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

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

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

			default:
				elog(ERROR, "unrecognized operation code: %d",
					 (int) operation);
				result = NULL;
				break;
		}

		/*
		 * check our tuple count.. if we've processed the proper number
		 * then quit, else loop again and process more tuples.	Zero
		 * numberTuples means no limit.
		 */
		current_tuple_count++;
		if (numberTuples && numberTuples == current_tuple_count)
			break;
	}

	/*
	 * Process AFTER EACH STATEMENT triggers
	 */
	switch (operation)
	{
		case CMD_UPDATE:
			ExecASUpdateTriggers(estate, estate->es_result_relation_info);
			break;
		case CMD_DELETE:
			ExecASDeleteTriggers(estate, estate->es_result_relation_info);
			break;
		case CMD_INSERT:
			ExecASInsertTriggers(estate, estate->es_result_relation_info);
			break;
		default:
			/* do nothing */
			break;
	}

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

/* ----------------------------------------------------------------
 *		ExecSelect
 *
 *		SELECTs are easy.. we just pass the tuple to the appropriate
 *		print function.  The only complexity is when we do a
 *		"SELECT 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
ExecSelect(TupleTableSlot *slot,
		   DestReceiver *dest,
		   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"
	 *
	 * XXX this probably ought to be replaced by a separate destination
	 */
	if (estate->es_into_relation_descriptor != NULL)
	{
		heap_insert(estate->es_into_relation_descriptor, tuple,
					estate->es_snapshot->curcid);
		IncrAppended();
	}

	/*
	 * send the tuple to the destination
	 */
	(*dest->receiveTuple) (tuple, attrtype, dest);
	IncrRetrieved();
	(estate->es_processed)++;
}

/* ----------------------------------------------------------------
 *		ExecInsert
 *
 *		INSERTs are trickier.. we have to insert the tuple into
 *		the base relation and insert appropriate tuples into the
 *		index relations.
 * ----------------------------------------------------------------
 */
static void
ExecInsert(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	HeapTuple	tuple;
	ResultRelInfo *resultRelInfo;
	Relation	resultRelationDesc;
	int			numIndices;
	Oid			newId;

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

	/*
	 * get information on the (current) result relation
	 */
	resultRelInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelInfo->ri_RelationDesc;

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

		newtuple = ExecBRInsertTriggers(estate, resultRelInfo, tuple);

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

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			/*
			 * Insert modified tuple into tuple table slot, replacing the
			 * original.  We assume that it was allocated in per-tuple
			 * memory context, and therefore will go away by itself. The
			 * tuple table slot should not try to clear it.
			 */
			ExecStoreTuple(newtuple, slot, InvalidBuffer, false);
			tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of the tuple
	 */
	if (resultRelationDesc->rd_att->constr)
		ExecConstraints(resultRelInfo, slot, estate);

	/*
	 * insert the tuple
	 */
	newId = heap_insert(resultRelationDesc, tuple,
						estate->es_snapshot->curcid);

	IncrAppended();
	(estate->es_processed)++;
	estate->es_lastoid = newId;
	setLastTid(&(tuple->t_self));

	/*
	 * 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 = resultRelInfo->ri_NumIndices;
	if (numIndices > 0)
		ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);

	/* AFTER ROW INSERT Triggers */
	ExecARInsertTriggers(estate, resultRelInfo, tuple);
}

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

	/*
	 * get information on the (current) result relation
	 */
	resultRelInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelInfo->ri_RelationDesc;

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

		dodelete = ExecBRDeleteTriggers(estate, resultRelInfo, tupleid,
										estate->es_snapshot->curcid);

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

	/*
	 * delete the tuple
	 */
ldelete:;
	result = heap_delete(resultRelationDesc, tupleid,
						 &ctid,
						 estate->es_snapshot->curcid,
						 estate->es_crosscheck_snapshot,
						 true /* wait for commit */);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			/* already deleted by self; nothing to do */
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				ereport(ERROR,
						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
						 errmsg("could not serialize access due to concurrent update")));
			else if (!(ItemPointerEquals(tupleid, &ctid)))
			{
				TupleTableSlot *epqslot = EvalPlanQual(estate,
							   resultRelInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					goto ldelete;
				}
			}
			/* tuple already deleted; nothing to do */
			return;

		default:
			elog(ERROR, "unrecognized heap_delete status: %u", 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 */
	ExecARDeleteTriggers(estate, resultRelInfo, tupleid);
}

/* ----------------------------------------------------------------
 *		ExecUpdate
 *
 *		note: we can't run UPDATE queries with transactions
 *		off because UPDATEs are actually INSERTs and our
 *		scan will mistakenly loop forever, updating the tuple
 *		it just inserted..	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
ExecUpdate(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	HeapTuple	tuple;
	ResultRelInfo *resultRelInfo;
	Relation	resultRelationDesc;
	ItemPointerData ctid;
	int			result;
	int			numIndices;

	/*
	 * abort the operation if not running transactions
	 */
	if (IsBootstrapProcessingMode())
		elog(ERROR, "cannot UPDATE during bootstrap");

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

	/*
	 * get information on the (current) result relation
	 */
	resultRelInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelInfo->ri_RelationDesc;

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

		newtuple = ExecBRUpdateTriggers(estate, resultRelInfo,
										tupleid, tuple,
										estate->es_snapshot->curcid);

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

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			/*
			 * Insert modified tuple into tuple table slot, replacing the
			 * original.  We assume that it was allocated in per-tuple
			 * memory context, and therefore will go away by itself. The
			 * tuple table slot should not try to clear it.
			 */
			ExecStoreTuple(newtuple, slot, InvalidBuffer, false);
			tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of the tuple
	 *
	 * If we generate a new candidate tuple after EvalPlanQual testing, we
	 * must loop back here and recheck constraints.  (We don't need to
	 * redo triggers, however.	If there are any BEFORE triggers then
	 * trigger.c will have done mark4update to lock the correct tuple, so
	 * there's no need to do them again.)
	 */
lreplace:;
	if (resultRelationDesc->rd_att->constr)
		ExecConstraints(resultRelInfo, slot, estate);

	/*
	 * replace the heap tuple
	 */
	result = heap_update(resultRelationDesc, tupleid, tuple,
						 &ctid,
						 estate->es_snapshot->curcid,
						 estate->es_crosscheck_snapshot,
						 true /* wait for commit */);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			/* already deleted by self; nothing to do */
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				ereport(ERROR,
						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
						 errmsg("could not serialize access due to concurrent update")));
			else if (!(ItemPointerEquals(tupleid, &ctid)))