src/main/java/net/hydromatic/optiq/impl/csv/CsvTableScan.java

/*
// Licensed to Julian Hyde under one or more contributor license
// agreements. See the NOTICE file distributed with this work for
// additional information regarding copyright ownership.
//
// Julian Hyde 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 net.hydromatic.optiq.impl.csv;

import net.hydromatic.optiq.rules.java.*;

import net.hydromatic.linq4j.expressions.*;

import org.eigenbase.rel.*;
import org.eigenbase.relopt.*;
import org.eigenbase.reltype.*;

import java.util.*;

/**
 * Relational expression representing a scan of a CSV file.
 *
 * <p>Like any table scan, it serves as a leaf node of a query tree.</p>
 */
public class CsvTableScan extends TableAccessRelBase implements EnumerableRel {
  final CsvTable csvTable;
  final int[] fields;

  protected CsvTableScan(RelOptCluster cluster, RelOptTable table,
      CsvTable csvTable, int[] fields) {
    super(cluster, cluster.traitSetOf(EnumerableConvention.INSTANCE), table);
    this.csvTable = csvTable;
    this.fields = fields;

    assert csvTable != null;
  }

  @Override
  public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
    assert inputs.isEmpty();
    return new CsvTableScan(getCluster(), table, csvTable, fields);
  }

  @Override
  public RelWriter explainTerms(RelWriter pw) {
    return super.explainTerms(pw)
        .item("fields", Primitive.asList(fields));
  }

  @Override
  public RelDataType deriveRowType() {
    final List<RelDataTypeField> fieldList = table.getRowType().getFieldList();
    final RelDataTypeFactory.FieldInfoBuilder builder =
        getCluster().getTypeFactory().builder();
    for (int field : fields) {
      builder.add(fieldList.get(field));
    }
    return builder.build();
  }

  @Override
  public void register(RelOptPlanner planner) {
    planner.addRule(CsvPushProjectOntoTableRule.INSTANCE);
  }

  public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
    PhysType physType =
        PhysTypeImpl.of(
            implementor.getTypeFactory(),
            getRowType(),
            pref.preferArray());

    if (table instanceof JsonTable) {
      return implementor.result(
          physType,
          Blocks.toBlock(
              Expressions.call(table.getExpression(JsonTable.class),
                  "enumerable")));
    }
    return implementor.result(
        physType,
        Blocks.toBlock(
            Expressions.call(table.getExpression(CsvTable.class), "project",
                Expressions.constant(fields))));
  }
}

// End CsvTableScan.java