sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rel/BeamPushDownIOSourceRel.java

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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.beam.sdk.extensions.sql.impl.rel;

import static org.apache.beam.vendor.calcite.v1_20_0.com.google.common.base.Preconditions.checkArgument;

import java.util.List;
import java.util.Map;
import org.apache.beam.sdk.extensions.sql.impl.BeamCalciteTable;
import org.apache.beam.sdk.extensions.sql.impl.planner.BeamCostModel;
import org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils;
import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTable;
import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTableFilter;
import org.apache.beam.sdk.extensions.sql.meta.DefaultTableFilter;
import org.apache.beam.sdk.schemas.Schema;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.values.PBegin;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionList;
import org.apache.beam.sdk.values.Row;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.plan.RelOptCluster;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.plan.RelOptPlanner;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.plan.RelOptTable;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.plan.RelTraitSet;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelWriter;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.metadata.RelMetadataQuery;

public class BeamPushDownIOSourceRel extends BeamIOSourceRel {
  private final List<String> usedFields;
  private final BeamSqlTableFilter tableFilters;

  public BeamPushDownIOSourceRel(
      RelOptCluster cluster,
      RelTraitSet traitSet,
      RelOptTable table,
      BeamSqlTable beamTable,
      List<String> usedFields,
      BeamSqlTableFilter tableFilters,
      Map<String, String> pipelineOptions,
      BeamCalciteTable calciteTable) {
    super(cluster, traitSet, table, beamTable, pipelineOptions, calciteTable);
    this.usedFields = usedFields;
    this.tableFilters = tableFilters;
  }

  @Override
  public RelWriter explainTerms(RelWriter pw) {
    super.explainTerms(pw);

    // This is done to tell Calcite planner that BeamIOSourceRel cannot be simply substituted by
    //  another BeamIOSourceRel, except for when they carry the same content.
    if (!usedFields.isEmpty()) {
      pw.item("usedFields", usedFields.toString());
    }
    if (!(tableFilters instanceof DefaultTableFilter)) {
      pw.item(tableFilters.getClass().getSimpleName(), tableFilters.toString());
    }

    return pw;
  }

  @Override
  public PTransform<PCollectionList<Row>, PCollection<Row>> buildPTransform() {
    return new Transform();
  }

  private class Transform extends PTransform<PCollectionList<Row>, PCollection<Row>> {

    @Override
    public PCollection<Row> expand(PCollectionList<Row> input) {
      checkArgument(
          input.size() == 0,
          "Should not have received input for %s: %s",
          BeamIOSourceRel.class.getSimpleName(),
          input);

      final PBegin begin = input.getPipeline().begin();
      final BeamSqlTable beamSqlTable = BeamPushDownIOSourceRel.this.getBeamSqlTable();

      if (usedFields.isEmpty() && tableFilters instanceof DefaultTableFilter) {
        return beamSqlTable.buildIOReader(begin);
      }

      final Schema newBeamSchema = CalciteUtils.toSchema(getRowType());
      return beamSqlTable
          .buildIOReader(begin, tableFilters, usedFields)
          .setRowSchema(newBeamSchema);
    }
  }

  @Override
  public BeamCostModel beamComputeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {
    return super.beamComputeSelfCost(planner, mq)
        .multiplyBy((double) 1 / (getRowType().getFieldCount() + 1));
  }
}