private void removeUnusedAssigns(
Mutable<ILogicalOperator> opRef, Set<LogicalVariable> toRemove, IOptimizationContext context)
throws AlgebricksException {
AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
while (removeFromAssigns(op, toRemove, context) == 0) {
if (op.getOperatorTag() == LogicalOperatorTag.AGGREGATE) {
break;
}
op = (AbstractLogicalOperator) op.getInputs().get(0).getValue();
opRef.setValue(op);
}
Iterator<Mutable<ILogicalOperator>> childIter = op.getInputs().iterator();
while (childIter.hasNext()) {
Mutable<ILogicalOperator> cRef = childIter.next();
removeUnusedAssigns(cRef, toRemove, context);
}
if (op.hasNestedPlans()) {
AbstractOperatorWithNestedPlans opWithNest = (AbstractOperatorWithNestedPlans) op;
Iterator<ILogicalPlan> planIter = opWithNest.getNestedPlans().iterator();
while (planIter.hasNext()) {
ILogicalPlan p = planIter.next();
for (Mutable<ILogicalOperator> r : p.getRoots()) {
removeUnusedAssigns(r, toRemove, context);
}
}
// Removes redundant nested plans that produces nothing
for (int i = opWithNest.getNestedPlans().size() - 1; i >= 0; i--) {
ILogicalPlan nestedPlan = opWithNest.getNestedPlans().get(i);
List<Mutable<ILogicalOperator>> rootsToBeRemoved =
new ArrayList<Mutable<ILogicalOperator>>();
for (Mutable<ILogicalOperator> r : nestedPlan.getRoots()) {
ILogicalOperator topOp = r.getValue();
Set<LogicalVariable> producedVars = new ListSet<LogicalVariable>();
VariableUtilities.getProducedVariablesInDescendantsAndSelf(topOp, producedVars);
if (producedVars.size() == 0) {
rootsToBeRemoved.add(r);
}
}
// Makes sure the operator should have at least ONE nested plan even it is empty
// (because a lot of places uses this assumption, TODO(yingyib): clean them up).
if (nestedPlan.getRoots().size() == rootsToBeRemoved.size()
&& opWithNest.getNestedPlans().size() > 1) {
nestedPlan.getRoots().removeAll(rootsToBeRemoved);
opWithNest.getNestedPlans().remove(nestedPlan);
}
}
}
}
private void collectUnusedAssignedVars(
AbstractLogicalOperator op,
Set<LogicalVariable> toRemove,
boolean first,
IOptimizationContext context)
throws AlgebricksException {
if (!first) {
context.addToDontApplySet(this, op);
}
for (Mutable<ILogicalOperator> c : op.getInputs()) {
collectUnusedAssignedVars((AbstractLogicalOperator) c.getValue(), toRemove, false, context);
}
if (op.hasNestedPlans()) {
AbstractOperatorWithNestedPlans opWithNested = (AbstractOperatorWithNestedPlans) op;
for (ILogicalPlan plan : opWithNested.getNestedPlans()) {
for (Mutable<ILogicalOperator> r : plan.getRoots()) {
collectUnusedAssignedVars(
(AbstractLogicalOperator) r.getValue(), toRemove, false, context);
}
}
}
boolean removeUsedVars = true;
switch (op.getOperatorTag()) {
case ASSIGN:
{
AssignOperator assign = (AssignOperator) op;
toRemove.addAll(assign.getVariables());
break;
}
case AGGREGATE:
{
AggregateOperator agg = (AggregateOperator) op;
toRemove.addAll(agg.getVariables());
break;
}
case UNNEST:
{
UnnestOperator uOp = (UnnestOperator) op;
LogicalVariable pVar = uOp.getPositionalVariable();
if (pVar != null) {
toRemove.add(pVar);
}
break;
}
case UNIONALL:
{
UnionAllOperator unionOp = (UnionAllOperator) op;
for (Triple<LogicalVariable, LogicalVariable, LogicalVariable> varMapping :
unionOp.getVariableMappings()) {
toRemove.add(varMapping.third);
}
removeUsedVars = false;
break;
}
}
if (removeUsedVars) {
List<LogicalVariable> used = new LinkedList<LogicalVariable>();
VariableUtilities.getUsedVariables(op, used);
toRemove.removeAll(used);
}
}
@Override
public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
throws AlgebricksException {
AbstractLogicalOperator unnest = (AbstractLogicalOperator) opRef.getValue();
if (unnest.getOperatorTag() != LogicalOperatorTag.UNNEST) {
return false;
}
UnnestOperator unnestOpRef = (UnnestOperator) opRef.getValue();
Mutable<ILogicalOperator> unionOp = unnest.getInputs().get(0);
AbstractLogicalOperator unionAbstractOp = (AbstractLogicalOperator) unionOp.getValue();
if (unionAbstractOp.getOperatorTag() != LogicalOperatorTag.UNIONALL) {
return false;
}
LogicalVariable unnestVar1 = context.newVar();
UnnestOperator unnest1 =
new UnnestOperator(
unnestVar1,
new MutableObject<ILogicalExpression>(
unnestOpRef.getExpressionRef().getValue().cloneExpression()));
LogicalVariable unnestVar2 = context.newVar();
UnnestOperator unnest2 =
new UnnestOperator(
unnestVar2,
new MutableObject<ILogicalExpression>(
unnestOpRef.getExpressionRef().getValue().cloneExpression()));
// Getting the two topmost branched and adding them as an input to the unnests:
Mutable<ILogicalOperator> branch1 = unionAbstractOp.getInputs().get(0);
ILogicalOperator agg1 = branch1.getValue();
List<LogicalVariable> agg1_var = new ArrayList<LogicalVariable>();
VariableUtilities.getLiveVariables(agg1, agg1_var);
Mutable<ILogicalOperator> branch2 = unionAbstractOp.getInputs().get(1);
ILogicalOperator agg2 = branch2.getValue();
List<LogicalVariable> agg2_var = new ArrayList<LogicalVariable>();
VariableUtilities.getLiveVariables(agg2, agg2_var);
// Modifying the unnest so it has the right variable
List<LogicalVariable> var_unnest_1 = new ArrayList<LogicalVariable>();
unnest1.getExpressionRef().getValue().getUsedVariables(var_unnest_1);
unnest1.getExpressionRef().getValue().substituteVar(var_unnest_1.get(0), agg1_var.get(0));
List<LogicalVariable> var_unnest2 = new ArrayList<LogicalVariable>();
unnest2.getExpressionRef().getValue().getUsedVariables(var_unnest2);
unnest2.getExpressionRef().getValue().substituteVar(var_unnest2.get(0), agg2_var.get(0));
unnest1.getInputs().add(branch1);
unnest2.getInputs().add(branch2);
context.computeAndSetTypeEnvironmentForOperator(unnest1);
context.computeAndSetTypeEnvironmentForOperator(unnest2);
// creating a new union operator with the updated logical variables
List<Triple<LogicalVariable, LogicalVariable, LogicalVariable>> varMap =
new ArrayList<Triple<LogicalVariable, LogicalVariable, LogicalVariable>>(1);
Triple<LogicalVariable, LogicalVariable, LogicalVariable> union_triple_vars =
new Triple<LogicalVariable, LogicalVariable, LogicalVariable>(
unnestVar1, unnestVar2, unnestOpRef.getVariables().get(0));
varMap.add(union_triple_vars);
UnionAllOperator unionOpFinal = new UnionAllOperator(varMap);
unionOpFinal.getInputs().add(new MutableObject<ILogicalOperator>(unnest1));
unionOpFinal.getInputs().add(new MutableObject<ILogicalOperator>(unnest2));
context.computeAndSetTypeEnvironmentForOperator(unionOpFinal);
opRef.setValue(unionOpFinal);
return true;
}
