execmain.c

PostgreSQL7.4.6 for Linux

			{
				TupleTableSlot *epqslot = EvalPlanQual(estate,
							   resultRelInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					tuple = ExecRemoveJunk(estate->es_junkFilter, epqslot);
					slot = ExecStoreTuple(tuple,
									estate->es_junkFilter->jf_resultSlot,
										  InvalidBuffer, true);
					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
	 */

	/*
	 * process indices
	 *
	 * heap_update updates a tuple in the base relation by invalidating it
	 * and then inserting a new tuple to the relation.	As a side effect,
	 * the tupleid of the new tuple is placed in the new tuple's t_ctid
	 * field.  So we now insert index tuples using the new tupleid stored
	 * there.
	 */

	numIndices = resultRelInfo->ri_NumIndices;
	if (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++)
		{
			qual = (List *) 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;
	HeapTuple	tuple = slot->val;
	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 &&
				heap_attisnull(tuple, 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.
 */
TupleTableSlot *
EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
{
	evalPlanQual *epq;
	EState	   *epqstate;
	Relation	relation;
	HeapTupleData tuple;
	HeapTuple	copyTuple = NULL;
	bool		endNode;

	Assert(rti != 0);

	/*
	 * find relation containing target tuple
	 */
	if (estate->es_result_relation_info != NULL &&
		estate->es_result_relation_info->ri_RangeTableIndex == rti)
		relation = estate->es_result_relation_info->ri_RelationDesc;
	else
	{
		List	   *l;

		relation = NULL;
		foreach(l, estate->es_rowMark)
		{
			if (((execRowMark *) lfirst(l))->rti == rti)
			{
				relation = ((execRowMark *) lfirst(l))->relation;
				break;
			}
		}
		if (relation == NULL)
			elog(ERROR, "could not find RowMark for RT index %u", rti);
	}

	/*
	 * fetch tid tuple
	 *
	 * Loop here to deal with updated or busy tuples
	 */
	tuple.t_self = *tid;
	for (;;)
	{
		Buffer		buffer;

		if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, false, NULL))
		{
			TransactionId xwait = SnapshotDirty->xmax;

			/* xmin should not be dirty... */
			if (TransactionIdIsValid(SnapshotDirty->xmin))
				elog(ERROR, "t_xmin is uncommitted in tuple to be updated");

			/*
			 * If tuple is being updated by other transaction then we have
			 * to wait for its commit/abort.
			 */
			if (TransactionIdIsValid(xwait))
			{
				ReleaseBuffer(buffer);
				XactLockTableWait(xwait);
				continue;
			}

			/*
			 * We got tuple - now copy it for use by recheck query.
			 */
			copyTuple = heap_copytuple(&tuple);
			ReleaseBuffer(buffer);
			break;
		}

		/*
		 * Oops! Invalid tuple. Have to check is it updated or deleted.
		 * Note that it's possible to get invalid SnapshotDirty->tid if
		 * tuple updated by this transaction. Have we to check this ?
		 */
		if (ItemPointerIsValid(&(SnapshotDirty->tid)) &&
			!(ItemPointerEquals(&(tuple.t_self), &(SnapshotDirty->tid))))
		{
			/* updated, so look at the updated copy */
			tuple.t_self = SnapshotDirty->tid;
			continue;
		}

		/*
		 * Deleted or updated by this transaction; forget it.
		 */
		return NULL;
	}

	/*
	 * For UPDATE/DELETE we have to return tid of actual row we're
	 * executing PQ for.
	 */
	*tid = tuple.t_self;

	/*
	 * Need to run a recheck subquery.	Find or create a PQ stack entry.
	 */
	epq = estate->es_evalPlanQual;
	endNode = true;

	if (epq != NULL && epq->rti == 0)
	{
		/* Top PQ stack entry is idle, so re-use it */
		Assert(!(estate->es_useEvalPlan) && epq->next == NULL);
		epq->rti = rti;
		endNode = false;
	}

	/*
	 * If this is request for another RTE - Ra, - then we have to check
	 * wasn't PlanQual requested for Ra already and if so then Ra' row was
	 * updated again and we have to re-start old execution for Ra and
	 * forget all what we done after Ra was suspended. Cool? -:))
	 */
	if (epq != NULL && epq->rti != rti &&
		epq->estate->es_evTuple[rti - 1] != NULL)
	{
		do
		{
			evalPlanQual *oldepq;

			/* stop execution */
			EvalPlanQualStop(epq);
			/* pop previous PlanQual from the stack */
			oldepq = epq->next;
			Assert(oldepq && oldepq->rti != 0);
			/* push current PQ to freePQ stack */
			oldepq->free = epq;
			epq = oldepq;
			estate->es_evalPlanQual = epq;
		} while (epq->rti != rti);
	}

	/*
	 * If we are requested for another RTE then we have to suspend
	 * execution of current PlanQual and start execution for new one.
	 */
	if (epq == NULL || epq->rti != rti)
	{
		/* try to reuse plan used previously */
		evalPlanQual *newepq = (epq != NULL) ? epq->free : NULL;

		if (newepq == NULL)		/* first call or freePQ stack is empty */
		{
			newepq = (evalPlanQual *) palloc0(sizeof(evalPlanQual));
			newepq->free = NULL;
			newepq->estate = NULL;
			newepq->planstate = NULL;
		}
		else
		{
			/* recycle previously used PlanQual */
			Assert(newepq->estate == NULL);
			epq->free = NULL;
		}
		/* push current PQ to the stack */
		newepq->next = epq;
		epq = newepq;
		estate->es_evalPlanQual = epq;
		epq->rti = rti;
		endNode = false;
	}

	Assert(epq->rti == rti);

	/*
	 * Ok - we're requested for the same RTE.  Unfortunately we still have
	 * to end and restart execution of the plan, because ExecReScan
	 * wouldn't ensure that upper plan nodes would reset themselves.  We
	 * could make that work if insertion of the target tuple were
	 * integrated with the Param mechanism somehow, so that the upper plan
	 * nodes know that their children's outputs have changed.
	 *
	 * Note that the stack of free evalPlanQual nodes is quite useless at the
	 * moment, since it only saves us from pallocing/releasing the
	 * evalPlanQual nodes themselves.  But it will be useful once we
	 * implement ReScan instead of end/restart for re-using PlanQual
	 * nodes.
	 */
	if (endNode)
	{
		/* stop execution */
		EvalPlanQualStop(epq);
	}

	/*
	 * Initialize new recheck query.
	 *
	 * Note: if we were re-using PlanQual plans via ExecReScan, we'd need to
	 * instead copy down changeable state from the top plan (including
	 * es_result_relation_info, es_junkFilter) and reset locally
	 * changeable state in the epq (including es_param_exec_vals,
	 * es_evTupleNull).
	 */
	EvalPlanQualStart(epq, estate, epq->next);

	/*
	 * free old RTE' tuple, if any, and store target tuple where
	 * relation's scan node will see it
	 */
	epqstate = epq->estate;
	if (epqstate->es_evTuple[rti - 1] != NULL)
		heap_freetuple(epqstate->es_evTuple[rti - 1]);
	epqstate->es_evTuple[rti - 1] = copyTuple;

	return EvalPlanQualNext(estate);
}

static TupleTableSlot *
EvalPlanQualNext(EState *estate)
{
	evalPlanQual *epq = estate->es_evalPlanQual;
	MemoryContext oldcontext;
	TupleTableSlot *slot;

	Assert(epq->rti != 0);

lpqnext:;
	oldcontext = MemoryContextSwitchTo(epq->estate->es_query_cxt);
	slot = ExecProcNode(epq->planstate);
	MemoryContextSwitchTo(oldcontext);

	/*
	 * No more tuples for this PQ. Continue previous one.
	 */
	if (TupIsNull(slot))
	{
		evalPlanQual *oldepq;

		/* stop execution */
		EvalPlanQualStop(epq);
		/* pop old PQ from the stack */
		oldepq = epq->next;
		if (oldepq == NULL)
		{
			/* this is the first (oldest) PQ - mark as free */
			epq->rti = 0;
			estate->es_useEvalPlan = false;
			/* and continue Query execution */
			return (NULL);
		}
		Assert(oldepq->rti != 0);
		/* push current PQ to freePQ stack */
		oldepq->free = epq;
		epq = oldepq;
		estate->es_evalPlanQual = epq;
		goto lpqnext;
	}

	return (slot);
}

static void
EndEvalPlanQual(EState *estate)
{
	evalPlanQual *epq = estate->es_evalPlanQual;

	if (epq->rti == 0)			/* plans already shutdowned */
	{
		Assert(epq->next == NULL);
		return;
	}

	for (;;)
	{
		evalPlanQual *oldepq;

		/* stop execution */
		EvalPlanQualStop(epq);
		/* pop old PQ from the stack */
		oldepq = epq->next;
		if (oldepq == NULL)
		{
			/* this is the first (oldest) PQ - mark as free */
			epq->rti = 0;
			estate->es_useEvalPlan = false;
			break;
		}
		Assert(oldepq->rti != 0);
		/* push current PQ to freePQ stack */
		oldepq->free = epq;
		epq = oldepq;
		estate->es_evalPlanQual = epq;
	}
}

/*
 * Start execution of one level of PlanQual.
 *
 * This is a cut-down version of ExecutorStart(): we copy some state from
 * the top-level estate rather than initializing it fresh.
 */
static void
EvalPlanQualStart(evalPlanQual *epq, EState *estate, evalPlanQual *priorepq)
{
	EState	   *epqstate;
	int			rtsize;
	MemoryContext oldcontext;

	rtsize = length(estate->es_range_table);

	epq->estate = epqstate = CreateExecutorState();

	oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);

	/*
	 * The epqstates share the top query's copy of unchanging state such
	 * as the snapshot, rangetable, result-rel info, and external Param
	 * info. They need their own copies of local state, including a tuple
	 * table, es_param_exec_vals, etc.
	 */
	epqstate->es_direction = ForwardScanDirection;
	epqstate->es_snapshot = estate->es_snapshot;
	epqstate->es_crosscheck_snapshot = estate->es_crosscheck_snapshot;
	epqstate->es_range_table = estate->es_range_table;
	epqstate->es_result_relations = estate->es_result_relations;
	epqstate->es_num_result_relations = estate->es_num_result_relations;
	epqstate->es_result_relation_info = estate->es_result_relation_info;
	epqstate->es_junkFilter = estate->es_junkFilter;
	epqstate->es_into_relation_descriptor = estate->es_into_relation_descriptor;
	epqstate->es_param_list_info = estate->es_param_list_info;
	if (estate->es_topPlan->nParamExec > 0)
		epqstate->es_param_exec_vals = (ParamExecData *)
			palloc0(estate->es_topPlan->nParamExec * sizeof(ParamExecData));
	epqstate->es_rowMark = estate->es_rowMark;
	epqstate->es_instrument = estate->es_instrument;
	epqstate->es_select_into = estate->es_select_into;
	epqstate->es_into_oids = estate->es_into_oids;
	epqstate->es_topPlan = estate->es_topPlan;

	/*
	 * Each epqstate must have its own es_evTupleNull state, but all the
	 * stack entries share es_evTuple state.  This allows sub-rechecks to
	 * inherit the value being examined by an outer recheck.
	 */
	epqstate->es_evTupleNull = (bool *) palloc0(rtsize * sizeof(bool));
	if (priorepq == NULL)
		/* first PQ stack entry */
		epqstate->es_evTuple = (HeapTuple *)
			palloc0(rtsize * sizeof(HeapTuple));
	else
		/* later stack entries share the same storage */
		epqstate->es_evTuple = priorepq->estate->es_evTuple;

	epqstate->es_tupleTable =
		ExecCreateTupleTable(estate->es_tupleTable->size);

	epq->planstate = ExecInitNode(estate->es_topPlan, epqstate);

	MemoryContextSwitchTo(oldcontext);
}

/*
 * End execution of one level of PlanQual.
 *
 * This is a cut-down version of ExecutorEnd(); basically we want to do most
 * of the normal cleanup, but *not* close result relations (which we are
 * just sharing from the outer query).
 */
static void
EvalPlanQualStop(evalPlanQual *epq)
{
	EState	   *epqstate = epq->estate;
	MemoryContext oldcontext;

	oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);

	ExecEndNode(epq->planstate);

	ExecDropTupleTable(epqstate->es_tupleTable, true);
	epqstate->es_tupleTable = NULL;

	if (epqstate->es_evTuple[epq->rti - 1] != NULL)
	{
		heap_freetuple(epqstate->es_evTuple[epq->rti - 1]);
		epqstate->es_evTuple[epq->rti - 1] = NULL;
	}

	MemoryContextSwitchTo(oldcontext);

	FreeExecutorState(epqstate);

	epq->estate = NULL;
	epq->planstate = NULL;
}