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A table format for huge analytic datasets
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/*
 * 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.iceberg;

import com.github.benmanes.caffeine.cache.Caffeine;
import com.github.benmanes.caffeine.cache.LoadingCache;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.iceberg.expressions.Expression;
import org.apache.iceberg.expressions.Expressions;
import org.apache.iceberg.expressions.ManifestEvaluator;
import org.apache.iceberg.expressions.ResidualEvaluator;
import org.apache.iceberg.io.CloseableIterable;
import org.apache.iceberg.io.FileIO;
import org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting;
import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
import org.apache.iceberg.relocated.com.google.common.collect.Maps;
import org.apache.iceberg.relocated.com.google.common.collect.Sets;
import org.apache.iceberg.types.TypeUtil;
import org.apache.iceberg.types.Types;
import org.apache.iceberg.types.Types.StructType;

/** Base class logic for files metadata tables */
abstract class BaseFilesTable extends BaseMetadataTable {

  BaseFilesTable(Table table, String name) {
    super(table, name);
  }

  @Override
  public Schema schema() {
    StructType partitionType = Partitioning.partitionType(table());
    Schema schema = new Schema(DataFile.getType(partitionType).fields());
    if (partitionType.fields().size() < 1) {
      // avoid returning an empty struct, which is not always supported. instead, drop the partition
      // field
      schema = TypeUtil.selectNot(schema, Sets.newHashSet(DataFile.PARTITION_ID));
    }

    return TypeUtil.join(schema, MetricsUtil.readableMetricsSchema(table().schema(), schema));
  }

  private static CloseableIterable planFiles(
      Table table,
      CloseableIterable manifests,
      Schema tableSchema,
      Schema projectedSchema,
      TableScanContext context) {
    Expression rowFilter = context.rowFilter();
    boolean caseSensitive = context.caseSensitive();
    boolean ignoreResiduals = context.ignoreResiduals();

    LoadingCache evalCache =
        Caffeine.newBuilder()
            .build(
                specId -> {
                  PartitionSpec spec = table.specs().get(specId);
                  PartitionSpec transformedSpec = BaseFilesTable.transformSpec(tableSchema, spec);
                  return ManifestEvaluator.forRowFilter(rowFilter, transformedSpec, caseSensitive);
                });

    CloseableIterable filteredManifests =
        CloseableIterable.filter(
            manifests, manifest -> evalCache.get(manifest.partitionSpecId()).eval(manifest));

    String schemaString = SchemaParser.toJson(projectedSchema);
    String specString = PartitionSpecParser.toJson(PartitionSpec.unpartitioned());
    Expression filter = ignoreResiduals ? Expressions.alwaysTrue() : rowFilter;
    ResidualEvaluator residuals = ResidualEvaluator.unpartitioned(filter);

    return CloseableIterable.transform(
        filteredManifests,
        manifest ->
            new ManifestReadTask(
                table, manifest, projectedSchema, schemaString, specString, residuals));
  }

  abstract static class BaseFilesTableScan extends BaseMetadataTableScan {

    protected BaseFilesTableScan(Table table, Schema schema, MetadataTableType tableType) {
      super(table, schema, tableType);
    }

    protected BaseFilesTableScan(
        Table table, Schema schema, MetadataTableType tableType, TableScanContext context) {
      super(table, schema, tableType, context);
    }

    /** Returns an iterable of manifest files to explore for this files metadata table scan */
    protected abstract CloseableIterable manifests();

    @Override
    protected CloseableIterable doPlanFiles() {
      return BaseFilesTable.planFiles(table(), manifests(), tableSchema(), schema(), context());
    }
  }

  abstract static class BaseAllFilesTableScan extends BaseAllMetadataTableScan {

    protected BaseAllFilesTableScan(Table table, Schema schema, MetadataTableType tableType) {
      super(table, schema, tableType);
    }

    protected BaseAllFilesTableScan(
        Table table, Schema schema, MetadataTableType tableType, TableScanContext context) {
      super(table, schema, tableType, context);
    }

    /** Returns an iterable of manifest files to explore for this all files metadata table scan */
    protected abstract CloseableIterable manifests();

    @Override
    protected CloseableIterable doPlanFiles() {
      return BaseFilesTable.planFiles(table(), manifests(), tableSchema(), schema(), context());
    }
  }

  static class ManifestReadTask extends BaseFileScanTask implements DataTask {

    private final FileIO io;
    private final Map specsById;
    private final ManifestFile manifest;
    private final Schema dataTableSchema;
    private final Schema projection;

    ManifestReadTask(
        Table table,
        ManifestFile manifest,
        Schema projection,
        String schemaString,
        String specString,
        ResidualEvaluator residuals) {
      super(DataFiles.fromManifest(manifest), null, schemaString, specString, residuals);
      this.io = table.io();
      this.specsById = Maps.newHashMap(table.specs());
      this.manifest = manifest;
      this.dataTableSchema = table.schema();
      this.projection = projection;
    }

    @Override
    public CloseableIterable rows() {
      Types.NestedField readableMetricsField = projection.findField(MetricsUtil.READABLE_METRICS);

      if (readableMetricsField == null) {
        return CloseableIterable.transform(files(projection), file -> (StructLike) file);
      } else {
        // Remove virtual columns from the file projection and ensure that the underlying metrics
        // used to create those columns are part of the file projection
        Set readableMetricsIds = TypeUtil.getProjectedIds(readableMetricsField.type());
        Schema fileProjection = TypeUtil.selectNot(projection, readableMetricsIds);
        int metricsPosition = projection.columns().indexOf(readableMetricsField);

        Schema projectionForReadableMetrics =
            new Schema(
                MetricsUtil.READABLE_METRIC_COLS.stream()
                    .map(MetricsUtil.ReadableMetricColDefinition::originalCol)
                    .collect(Collectors.toList()));

        Schema projectionForMetrics = TypeUtil.join(fileProjection, projectionForReadableMetrics);
        return CloseableIterable.transform(
            files(projectionForMetrics), f -> withReadableMetrics(f, metricsPosition));
      }
    }

    private CloseableIterable> files(Schema fileProjection) {
      switch (manifest.content()) {
        case DATA:
          return ManifestFiles.read(manifest, io, specsById).project(fileProjection);
        case DELETES:
          return ManifestFiles.readDeleteManifest(manifest, io, specsById).project(fileProjection);
        default:
          throw new IllegalArgumentException(
              "Unsupported manifest content type:" + manifest.content());
      }
    }

    private StructLike withReadableMetrics(ContentFile file, int metricsPosition) {
      int columnCount = projection.columns().size();
      StructType projectedMetricType =
          projection.findField(MetricsUtil.READABLE_METRICS).type().asStructType();
      MetricsUtil.ReadableMetricsStruct readableMetrics =
          MetricsUtil.readableMetricsStruct(dataTableSchema, file, projectedMetricType);
      return new ContentFileStructWithMetrics(
          columnCount, metricsPosition, (StructLike) file, readableMetrics);
    }

    @Override
    public Iterable split(long splitSize) {
      return ImmutableList.of(this); // don't split
    }

    @VisibleForTesting
    ManifestFile manifest() {
      return manifest;
    }
  }

  static class ContentFileStructWithMetrics implements StructLike {
    private final StructLike fileAsStruct;
    private final MetricsUtil.ReadableMetricsStruct readableMetrics;
    private final int columnCount;
    private final int metricsPosition;

    ContentFileStructWithMetrics(
        int columnCount,
        int metricsPosition,
        StructLike fileAsStruct,
        MetricsUtil.ReadableMetricsStruct readableMetrics) {
      this.fileAsStruct = fileAsStruct;
      this.readableMetrics = readableMetrics;
      this.columnCount = columnCount;
      this.metricsPosition = metricsPosition;
    }

    @Override
    public int size() {
      return columnCount;
    }

    @Override
    public  T get(int pos, Class javaClass) {
      if (pos < metricsPosition) {
        return fileAsStruct.get(pos, javaClass);
      } else if (pos == metricsPosition) {
        return javaClass.cast(readableMetrics);
      } else {
        // columnCount = fileAsStruct column count + the readable metrics field.
        // When pos is greater than metricsPosition, the actual position of the field in
        // fileAsStruct should be subtracted by 1.
        return fileAsStruct.get(pos - 1, javaClass);
      }
    }

    @Override
    public  void set(int pos, T value) {
      throw new UnsupportedOperationException("ContentFileStructWithMetrics is read only");
    }
  }
}