@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;
}
