execmain.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

 *		index relations.
 * ----------------------------------------------------------------
 */
static void
ExecInsert(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	HeapTuple	tuple;
	ResultRelInfo *resultRelInfo;
	Relation	resultRelationDesc;
	Oid			newId;

	/*
	 * get the heap tuple out of the tuple table slot, making sure we have a
	 * writable copy
	 */
	tuple = ExecMaterializeSlot(slot);

	/*
	 * 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) */
		{
			/*
			 * Put the modified tuple into a slot for convenience of routines
			 * below.  We assume the tuple was allocated in per-tuple memory
			 * context, and therefore will go away by itself. The tuple table
			 * slot should not try to clear it.
			 */
			TupleTableSlot *newslot = estate->es_trig_tuple_slot;

			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
				ExecSetSlotDescriptor(newslot,
									  slot->tts_tupleDescriptor,
									  false);
			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
			slot = newslot;
			tuple = newtuple;
		}
	}

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

	/*
	 * insert the tuple
	 *
	 * Note: heap_insert returns the tid (location) of the new tuple in the
	 * t_self field.
	 */
	newId = heap_insert(resultRelationDesc, tuple,
						estate->es_snapshot->curcid,
						true, true);

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

	/*
	 * insert index entries for tuple
	 */
	if (resultRelInfo->ri_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;
	HTSU_Result result;
	ItemPointerData update_ctid;
	TransactionId update_xmax;

	/*
	 * 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
	 *
	 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that
	 * the row to be deleted is visible to that snapshot, and throw a can't-
	 * serialize error if not.	This is a special-case behavior needed for
	 * referential integrity updates in serializable transactions.
	 */
ldelete:;
	result = heap_delete(resultRelationDesc, tupleid,
						 &update_ctid, &update_xmax,
						 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 (IsXactIsoLevelSerializable)
				ereport(ERROR,
						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
						 errmsg("could not serialize access due to concurrent update")));
			else if (!ItemPointerEquals(tupleid, &update_ctid))
			{
				TupleTableSlot *epqslot;

				epqslot = EvalPlanQual(estate,
									   resultRelInfo->ri_RangeTableIndex,
									   &update_ctid,
									   update_xmax,
									   estate->es_snapshot->curcid);
				if (!TupIsNull(epqslot))
				{
					*tupleid = update_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;
	HTSU_Result result;
	ItemPointerData update_ctid;
	TransactionId update_xmax;

	/*
	 * 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, making sure we have a
	 * writable copy
	 */
	tuple = ExecMaterializeSlot(slot);

	/*
	 * 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) */
		{
			/*
			 * Put the modified tuple into a slot for convenience of routines
			 * below.  We assume the tuple was allocated in per-tuple memory
			 * context, and therefore will go away by itself. The tuple table
			 * slot should not try to clear it.
			 */
			TupleTableSlot *newslot = estate->es_trig_tuple_slot;

			if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
				ExecSetSlotDescriptor(newslot,
									  slot->tts_tupleDescriptor,
									  false);
			ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
			slot = newslot;
			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 heap_lock_tuple 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
	 *
	 * Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that
	 * the row to be updated is visible to that snapshot, and throw a can't-
	 * serialize error if not.	This is a special-case behavior needed for
	 * referential integrity updates in serializable transactions.
	 */
	result = heap_update(resultRelationDesc, tupleid, tuple,
						 &update_ctid, &update_xmax,
						 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 (IsXactIsoLevelSerializable)
				ereport(ERROR,
						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
						 errmsg("could not serialize access due to concurrent update")));
			else if (!ItemPointerEquals(tupleid, &update_ctid))
			{
				TupleTableSlot *epqslot;

				epqslot = EvalPlanQual(estate,
									   resultRelInfo->ri_RangeTableIndex,
									   &update_ctid,
									   update_xmax,
									   estate->es_snapshot->curcid);
				if (!TupIsNull(epqslot))
				{
					*tupleid = update_ctid;
					slot = ExecFilterJunk(estate->es_junkFilter, epqslot);
					tuple = ExecMaterializeSlot(slot);
					goto lreplace;
				}
			}
			/* tuple already deleted; nothing to do */
			return;

		default:
			elog(ERROR, "unrecognized heap_update status: %u", result);
			return;
	}

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

	/*
	 * Note: instead of having to update the old index tuples associated with
	 * the heap tuple, all we do is form and insert new index tuples. This is
	 * because UPDATEs are actually DELETEs and INSERTs, and index tuple
	 * deletion is done automagically by the vacuum daemon. All we do is
	 * insert new index tuples.  -cim 9/27/89
	 */

	/*
	 * insert index entries for tuple
	 *
	 * Note: heap_update returns the tid (location) of the new tuple in the
	 * t_self field.
	 */
	if (resultRelInfo->ri_NumIndices > 0)
		ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);

	/* AFTER ROW UPDATE Triggers */
	ExecARUpdateTriggers(estate, resultRelInfo, tupleid, tuple);
}

static const char *
ExecRelCheck(ResultRelInfo *resultRelInfo,
			 TupleTableSlot *slot, EState *estate)
{
	Relation	rel = resultRelInfo->ri_RelationDesc;
	int			ncheck = rel->rd_att->constr->num_check;
	ConstrCheck *check = rel->rd_att->constr->check;
	ExprContext *econtext;
	MemoryContext oldContext;
	List	   *qual;
	int			i;

	/*
	 * If first time through for this result relation, build expression
	 * nodetrees for rel's constraint expressions.  Keep them in the per-query
	 * memory context so they'll survive throughout the query.
	 */
	if (resultRelInfo->ri_ConstraintExprs == NULL)
	{
		oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
		resultRelInfo->ri_ConstraintExprs =
			(List **) palloc(ncheck * sizeof(List *));
		for (i = 0; i < ncheck; i++)
		{
			/* ExecQual wants implicit-AND form */
			qual = make_ands_implicit(stringToNode(check[i].ccbin));
			resultRelInfo->ri_ConstraintExprs[i] = (List *)
				ExecPrepareExpr((Expr *) qual, estate);
		}
		MemoryContextSwitchTo(oldContext);
	}

	/*
	 * We will use the EState's per-tuple context for evaluating constraint
	 * expressions (creating it if it's not already there).
	 */
	econtext = GetPerTupleExprContext(estate);

	/* Arrange for econtext's scan tuple to be the tuple under test */
	econtext->ecxt_scantuple = slot;

	/* And evaluate the constraints */
	for (i = 0; i < ncheck; i++)
	{
		qual = resultRelInfo->ri_ConstraintExprs[i];

		/*
		 * NOTE: SQL92 specifies that a NULL result from a constraint
		 * expression is not to be treated as a failure.  Therefore, tell
		 * ExecQual to return TRUE for NULL.
		 */
		if (!ExecQual(qual, econtext, true))
			return check[i].ccname;
	}

	/* NULL result means no error */
	return NULL;
}

void
ExecConstraints(ResultRelInfo *resultRelInfo,
				TupleTableSlot *slot, EState *estate)
{
	Relation	rel = resultRelInfo->ri_RelationDesc;
	TupleConstr *constr = rel->rd_att->constr;

	Assert(constr);

	if (constr->has_not_null)
	{
		int			natts = rel->rd_att->natts;
		int			attrChk;

		for (attrChk = 1; attrChk <= natts; attrChk++)
		{
			if (rel->rd_att->attrs[attrChk - 1]->attnotnull &&
				slot_attisnull(slot, attrChk))
				ereport(ERROR,
						(errcode(ERRCODE_NOT_NULL_VIOLATION),
						 errmsg("null value in column \"%s\" violates not-null constraint",
						NameStr(rel->rd_att->attrs[attrChk - 1]->attname))));
		}
	}

	if (constr->num_check > 0)
	{
		const char *failed;

		if ((failed = ExecRelCheck(resultRelInfo, slot, estate)) != NULL)
			ereport(ERROR,
					(errcode(ERRCODE_CHECK_VIOLATION),
					 errmsg("new row for relation \"%s\" violates check constraint \"%s\"",
							RelationGetRelationName(rel), failed)));
	}
}

/*
 * Check a modified tuple to see if we want to process its updated version
 * under READ COMMITTED rules.
 *
 * See backend/executor/README for some info about how this works.
 *
 *	estate - executor state data
 *	rti - rangetable index of table containing tuple
 *	*tid - t_ctid from the outdated tuple (ie, next updated version)
 *	priorXmax - t_xmax from the outdated tuple
 *	curCid - command ID of current command of my transaction