abstract IncrementalIndex cursor stuff to prepare for using differe…

…nt "views" of the data based on the cursor build spec (#17064)

* abstract `IncrementalIndex` cursor stuff to prepare to allow for possibility of using different "views" of the data based on the cursor build spec
changes:
* introduce `IncrementalIndexRowSelector` interface to capture how `IncrementalIndexCursor` and `IncrementalIndexColumnSelectorFactory` read data
* `IncrementalIndex` implements `IncrementalIndexRowSelector`
* move `FactsHolder` interface to separate file
* other minor refactorings

processing/src/main/java/org/apache/druid/segment/incremental/FactsHolder.java

@@ -0,0 +1,82 @@
+/*
+ * 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.incremental;
+
+import java.util.Comparator;
+import java.util.Iterator;
+
+/**
+ * {@link IncrementalIndexRow} storage interface, a mutable data structure for building up a set or rows to eventually
+ * persist into an immutable segment
+ *
+ * @see IncrementalIndex for the data processor which constructs {@link IncrementalIndexRow} to store here
+ */
+public interface FactsHolder
+{
+  /**
+   * @return the previous rowIndex associated with the specified key, or
+   * {@link IncrementalIndexRow#EMPTY_ROW_INDEX} if there was no mapping for the key.
+   */
+  int getPriorIndex(IncrementalIndexRow key);
+
+  /**
+   * Get minimum {@link IncrementalIndexRow#getTimestamp()} present in the facts holder
+   */
+  long getMinTimeMillis();
+
+  /**
+   * Get maximum {@link IncrementalIndexRow#getTimestamp()} present in the facts holder
+   */
+  long getMaxTimeMillis();
+
+  /**
+   * Get all {@link IncrementalIndex}, depending on the implementation, these rows may or may not be ordered in the same
+   * order they will be persisted in. Use {@link #persistIterable()} if this is required.
+   */
+  Iterator<IncrementalIndexRow> iterator(boolean descending);
+
+  /**
+   * Get all {@link IncrementalIndexRow} with {@link IncrementalIndexRow#getTimestamp()} between the start and end
+   * timestamps specified
+   */
+  Iterable<IncrementalIndexRow> timeRangeIterable(boolean descending, long timeStart, long timeEnd);
+
+  /**
+   * Get all row {@link IncrementalIndexRow} 'keys', which is distinct groups if this is an aggregating facts holder or
+   * just every row present if not
+   */
+  Iterable<IncrementalIndexRow> keySet();
+
+  /**
+   * Get all {@link IncrementalIndexRow} to persist, ordered with {@link Comparator <IncrementalIndexRow>}
+   */
+  Iterable<IncrementalIndexRow> persistIterable();
+
+  /**
+   * @return the previous rowIndex associated with the specified key, or
+   * {@link IncrementalIndexRow#EMPTY_ROW_INDEX} if there was no mapping for the key.
+   */
+  int putIfAbsent(IncrementalIndexRow key, int rowIndex);
+
+  /**
+   * Clear all rows present in the facts holder
+   */
+  void clear();
+}