private void reduceNotNullableFilter(
RelOptRuleCall call, FilterRel filter, RexCall rexCall, boolean reverse) {
// If the expression is a IS [NOT] NULL on a non-nullable
// column, then we can either remove the filter or replace
// it with an EmptyRel.
SqlOperator op = rexCall.getOperator();
boolean alwaysTrue;
if (op == SqlStdOperatorTable.isNullOperator
|| op == SqlStdOperatorTable.isUnknownOperator) {
alwaysTrue = false;
} else if (op == SqlStdOperatorTable.isNotNullOperator) {
alwaysTrue = true;
} else {
return;
}
if (reverse) {
alwaysTrue = !alwaysTrue;
}
RexNode operand = rexCall.getOperands()[0];
if (operand instanceof RexInputRef) {
RexInputRef inputRef = (RexInputRef) operand;
if (!inputRef.getType().isNullable()) {
if (alwaysTrue) {
call.transformTo(filter.getChild());
} else {
call.transformTo(new EmptyRel(filter.getCluster(), filter.getRowType()));
}
}
}
}
public void onMatch(RelOptRuleCall call) {
FilterRel filter = (FilterRel) call.rels[0];
List<RexNode> expList = new ArrayList<RexNode>(Arrays.asList(filter.getChildExps()));
RexNode newConditionExp;
boolean reduced;
if (reduceExpressions(filter, expList)) {
assert (expList.size() == 1);
newConditionExp = expList.get(0);
reduced = true;
} else {
// No reduction, but let's still test the original
// predicate to see if it was already a constant,
// in which case we don't need any runtime decision
// about filtering.
newConditionExp = filter.getChildExps()[0];
reduced = false;
}
if (newConditionExp.isAlwaysTrue()) {
call.transformTo(filter.getChild());
} else if ((newConditionExp instanceof RexLiteral)
|| RexUtil.isNullLiteral(newConditionExp, true)) {
call.transformTo(new EmptyRel(filter.getCluster(), filter.getRowType()));
} else if (reduced) {
call.transformTo(CalcRel.createFilter(filter.getChild(), expList.get(0)));
} else {
if (newConditionExp instanceof RexCall) {
RexCall rexCall = (RexCall) newConditionExp;
boolean reverse = (rexCall.getOperator() == SqlStdOperatorTable.notOperator);
if (reverse) {
rexCall = (RexCall) rexCall.getOperands()[0];
}
reduceNotNullableFilter(call, filter, rexCall, reverse);
}
return;
}
// New plan is absolutely better than old plan.
call.getPlanner().setImportance(filter, 0.0);
}