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())); } } } }