a cleaner way to handle this

a cleaner way to handle this

https://github.com/apache/wayang/blob/c2bb03c469cb7d79583cc46153d68951894598e0/wayang-api/wayang-api-sql/src/main/java/org/apache/wayang/api/sql/calcite/rules/WayangTableScanRule.java#L56

```java

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.apache.wayang.api.sql.calcite.rules;

import org.apache.calcite.adapter.enumerable.EnumerableConvention;
import org.apache.calcite.plan.Convention;
import org.apache.calcite.plan.RelOptTable;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.convert.ConverterRule;
import org.apache.calcite.rel.core.TableScan;
import org.apache.calcite.rel.logical.LogicalTableScan;

import org.apache.wayang.api.sql.calcite.convention.WayangConvention;
import org.apache.wayang.api.sql.calcite.rel.WayangTableScan;

public class WayangTableScanRule extends ConverterRule {
public static final Config DEFAULT_CONFIG = Config.INSTANCE
.withConversion(LogicalTableScan.class,
Convention.NONE, WayangConvention.INSTANCE,
"WayangTableScanRule")
.withRuleFactory(WayangTableScanRule::new);

public static final Config ENUMERABLE_CONFIG = Config.INSTANCE
.withConversion(TableScan.class,
EnumerableConvention.INSTANCE, WayangConvention.INSTANCE,
"WayangTableScanRule1")
.withRuleFactory(WayangTableScanRule::new);

protected WayangTableScanRule(final Config config) {
super(config);
}

@Override
public RelNode convert(final RelNode relNode) {

final TableScan scan = (TableScan) relNode;
final RelOptTable relOptTable = scan.getTable();

/**
* This is quick hack to prevent volcano from merging projects on to TableScans
* TODO: a cleaner way to handle this
*/
if (relOptTable.getRowType() == scan.getRowType()) {
return WayangTableScan.create(scan.getCluster(), relOptTable);
}
return null;
}
}

```

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