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A module that is everything required to understands Druid Segments

There is a newer version: 30.0.1

/*
 * 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.druid.segment;

import org.apache.druid.math.expr.Expr;
import org.apache.druid.math.expr.ExpressionType;
import org.apache.druid.segment.column.ColumnCapabilities;

import javax.annotation.Nullable;

public interface ColumnInspector extends Expr.InputBindingInspector
{
  /**
   * Returns capabilities of a particular column.
   *
   * @param column column name
   *
   * @return capabilities, or null
   */
  @Nullable
  ColumnCapabilities getColumnCapabilities(String column);

  default ColumnCapabilities getColumnCapabilitiesWithDefault(String column, ColumnCapabilities defaultCapabilites)
  {
    final ColumnCapabilities capabilities = getColumnCapabilities(column);
    if (capabilities != null) {
      return capabilities;
    }
    return defaultCapabilites;
  }

  @Nullable
  @Override
  default ExpressionType getType(String name)
  {
    ColumnCapabilities capabilities = getColumnCapabilities(name);
    if (capabilities != null) {
      return ExpressionType.fromColumnType(capabilities);
    }
    return null;
  }
}