content: /*
   * 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 accord.api;
  
  import javax.annotation.Nullable;
  
  import accord.local.CommandStore;
  import accord.local.SafeCommandStore;
  import accord.primitives.Participants;
  import accord.primitives.Ranges;
  import accord.primitives.Seekable;
  import accord.primitives.Seekables;
  import accord.primitives.Timestamp;
  import accord.utils.async.AsyncChain;
  
  /**
   * A read to be performed on potentially multiple shards, the inputs of which may be fed to a {@link Query}
   */
  public interface Read
  {
      Seekables<?, ?> keys();
  
      /**
       * Issue a potentially-asynchronous read against the underlying data store while owning the SafeCommandStore.
       * The result is expected to be non-null unless the store determined the data was stale.
       * @param key MAY BE NULL indicating a no-op result should be returned
       */
      AsyncChain<Data> read(SafeCommandStore safeStore, @Nullable Seekable key, Timestamp executeAt);
  
      /**
       * Issue a potentially-asynchronous read against the underlying data store, while not owning the SafeCommandStore.
       * This method is only invoked if {@link ProtocolModifiers.Toggles#fastReadsMayBypassSafeStore()} is true.
       * The result is expected to be non-null unless the store determined the data was stale.
       * @param key MAY BE NULL indicating a no-op result should be returned
       */
      default AsyncChain<Data> readDirect(CommandStore commandStore, @Nullable Seekable key, Timestamp executeAt) { throw new UnsupportedOperationException(); }
      Read slice(Ranges ranges);
      Read intersecting(Participants<?> participants);
      Read merge(Read other);
  
  }
  