import quincy 17.2.0

[ceph.git] / ceph / src / arrow / java / algorithm / src / main / java / org / apache / arrow / algorithm / dictionary / DictionaryBuilder.java

diff --git a/ceph/src/arrow/java/algorithm/src/main/java/org/apache/arrow/algorithm/dictionary/DictionaryBuilder.java b/ceph/src/arrow/java/algorithm/src/main/java/org/apache/arrow/algorithm/dictionary/DictionaryBuilder.java
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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.arrow.algorithm.dictionary;
+
+import org.apache.arrow.vector.ValueVector;
+
+/**
+ * A dictionary builder is intended for the scenario frequently encountered in practice:
+ * the dictionary is not known a priori, so it is generated dynamically.
+ * In particular, when a new value arrives, it is tested to check if it is already
+ * in the dictionary. If so, it is simply neglected, otherwise, it is added to the dictionary.
+ * <p>
+ *   The dictionary builder is intended to build a single dictionary.
+ *   So it cannot be used for different dictionaries.
+ * </p>
+ * <p>Below gives the sample code for using the dictionary builder
+ * <pre>{@code
+ * DictionaryBuilder dictionaryBuilder = ...
+ * ...
+ * dictionaryBuild.addValue(newValue);
+ * ...
+ * }</pre>
+ * </p>
+ * <p>
+ *   With the above code, the dictionary vector will be populated,
+ *   and it can be retrieved by the {@link DictionaryBuilder#getDictionary()} method.
+ *   After that, dictionary encoding can proceed with the populated dictionary..
+ * </p>
+ *
+ * @param <V> the dictionary vector type.
+ */
+public interface DictionaryBuilder<V extends ValueVector> {
+
+  /**
+   * Try to add all values from the target vector to the dictionary.
+   *
+   * @param targetVector the target vector containing values to probe.
+   * @return the number of values actually added to the dictionary.
+   */
+  int addValues(V targetVector);
+
+  /**
+   * Try to add an element from the target vector to the dictionary.
+   *
+   * @param targetVector the target vector containing new element.
+   * @param targetIndex  the index of the new element in the target vector.
+   * @return the index of the new element in the dictionary.
+   */
+  int addValue(V targetVector, int targetIndex);
+
+  /**
+   * Gets the dictionary built.
+   *
+   * @return the dictionary.
+   */
+  V getDictionary();
+}