Chunwei Lei created CALCITE-3630:
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Summary: Improve ReduceExpressionsRule
Key: CALCITE-3630
URL: https://issues.apache.org/jira/browse/CALCITE-3630
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.21.0
Reporter: Chunwei Lei
Assignee: Chunwei Lei
In {{FilterReduceExpressionsRule}}, 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
Empty(namely {{reduceNotNullableFilter}}). In such a case, we can set
importance to 0 to reduce search space.
{code:java}
// code placeholder
private void reduceNotNullableFilter(
RelOptRuleCall call,
Filter filter,
RexNode rexNode,
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 Empty.
boolean alwaysTrue;
switch (rexNode.getKind()) {
case IS_NULL:
case IS_UNKNOWN:
alwaysTrue = false;
break;
case IS_NOT_NULL:
alwaysTrue = true;
break;
default:
return;
}
if (reverse) {
alwaysTrue = !alwaysTrue;
}
RexNode operand = ((RexCall) rexNode).getOperands().get(0);
if (operand instanceof RexInputRef) {
RexInputRef inputRef = (RexInputRef) operand;
if (!inputRef.getType().isNullable()) {
if (alwaysTrue) {
call.transformTo(filter.getInput());
} else {
call.transformTo(createEmptyRelOrEquivalent(call, filter));
}
// New plan is absolutely better than old plan.
call.getPlanner().setImportance(filter, 0.0);
}
}
}
}
{code}
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