Save a metadata call when reading files from CloudObjectInputSource. (#14677)

* Save a metadata call when reading files from CloudObjectInputSource.

The call to createSplits(inputFormat, null) in formattableReader would
use the default split hint spec, MaxSizeSplitHintSpec, which makes
getObjectMetadata calls in order to compute its splits. This isn't
necessary; we're just trying to unpack the files inside the input
source.

To fix this, use FilePerSplitHintSpec to extract files without any
funny business.

* Adjust call.

* Fix constant.

* Test coverage.

extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/input/external/ExternalInputSpecSlicer.java

@@ -19,8 +19,8 @@
 
 package org.apache.druid.msq.input.external;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Iterators;
+import org.apache.druid.data.input.FilePerSplitHintSpec;
 import org.apache.druid.data.input.InputFileAttribute;
 import org.apache.druid.data.input.InputSource;
 import org.apache.druid.data.input.InputSplit;
@@ -238,27 +238,4 @@ public class ExternalInputSpecSlicer implements InputSpecSlicer
       );
     }
   }
-
-  /**
-   * Assigns each input file to its own split.
-   */
-  @VisibleForTesting
-  static class FilePerSplitHintSpec implements SplitHintSpec
-  {
-    static FilePerSplitHintSpec INSTANCE = new FilePerSplitHintSpec();
-
-    private FilePerSplitHintSpec()
-    {
-      // Singleton.
-    }
-
-    @Override
-    public <T> Iterator<List<T>> split(
-        final Iterator<T> inputIterator,
-        final Function<T, InputFileAttribute> inputAttributeExtractor
-    )
-    {
-      return Iterators.transform(inputIterator, Collections::singletonList);
-    }
-  }
 }

processing/src/main/java/org/apache/druid/data/input/FilePerSplitHintSpec.java

@@ -0,0 +1,53 @@
+/*
+ * 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.data.input;
+
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.google.common.collect.Iterators;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.Function;
+
+/**
+ * Assigns each input file to its own split.
+ *
+ * Not named as a {@link JsonSubTypes} in {@link SplitHintSpec}, because this class is meant for internal use
+ * within a server only. It is not serialized for transfer between servers, and is not part of the user-facing API.
+ */
+public class FilePerSplitHintSpec implements SplitHintSpec
+{
+  public static final FilePerSplitHintSpec INSTANCE = new FilePerSplitHintSpec();
+
+  private FilePerSplitHintSpec()
+  {
+    // Singleton.
+  }
+
+  @Override
+  public <T> Iterator<List<T>> split(
+      final Iterator<T> inputIterator,
+      final Function<T, InputFileAttribute> inputAttributeExtractor
+  )
+  {
+    return Iterators.transform(inputIterator, Collections::singletonList);
+  }
+}

processing/src/main/java/org/apache/druid/data/input/impl/CloudObjectInputSource.java

@@ -26,6 +26,7 @@ import com.google.common.collect.Lists;
 import com.google.common.primitives.Ints;
 import org.apache.commons.lang.StringUtils;
 import org.apache.druid.data.input.AbstractInputSource;
+import org.apache.druid.data.input.FilePerSplitHintSpec;
 import org.apache.druid.data.input.InputEntity;
 import org.apache.druid.data.input.InputFileAttribute;
 import org.apache.druid.data.input.InputFormat;
@@ -173,11 +174,26 @@ public abstract class CloudObjectInputSource extends AbstractInputSource
     return new InputEntityIteratingReader(
         inputRowSchema,
         inputFormat,
-        createSplits(inputFormat, null).flatMap(split -> split.get().stream()).map(this::createEntity).iterator(),
+        getInputEntities(inputFormat),
         temporaryDirectory
     );
   }
 
+  /**
+   * Return an iterator of {@link InputEntity} corresponding to the objects represented by this input source, as read
+   * by the provided {@link InputFormat}.
+   */
+  Iterator<InputEntity> getInputEntities(final InputFormat inputFormat)
+  {
+    // Use createSplits with FilePerSplitHintSpec.INSTANCE as a way of getting the list of objects to read
+    // out of either "prefixes", "objects", or "uris". The specific splits don't matter because we are going
+    // to flatten them anyway.
+    return createSplits(inputFormat, FilePerSplitHintSpec.INSTANCE)
+        .flatMap(split -> split.get().stream())
+        .map(this::createEntity)
+        .iterator();
+  }
+
   @Override
   public boolean equals(Object o)
   {
@@ -311,7 +327,8 @@ public abstract class CloudObjectInputSource extends AbstractInputSource
                   long size = splitWidget.getObjectSize(o.getLocation());
                   return new InputFileAttribute(
                       size,
-                      inputFormat != null ? inputFormat.getWeightedSize(o.getLocation().getPath(), size) : size);
+                      inputFormat != null ? inputFormat.getWeightedSize(o.getLocation().getPath(), size) : size
+                  );
                 } else {
                   return new InputFileAttribute(
                       o.getSize(),

processing/src/test/java/org/apache/druid/data/input/impl/CloudObjectInputSourceTest.java

@@ -19,6 +19,8 @@
 
 package org.apache.druid.data.input.impl;
 
+import com.google.common.collect.Lists;
+import org.apache.druid.data.input.InputEntity;
 import org.apache.druid.data.input.InputSplit;
 import org.apache.druid.data.input.MaxSizeSplitHintSpec;
 import org.apache.druid.java.util.common.parsers.JSONPathSpec;
@@ -146,6 +148,10 @@ public class CloudObjectInputSourceTest
 
     Assert.assertEquals("**.csv", inputSource.getObjectGlob());
     Assert.assertEquals(URIS, returnedLocationUris);
+
+    final List<InputEntity> entities =
+        Lists.newArrayList(inputSource.getInputEntities(new JsonInputFormat(null, null, null, null, null)));
+    Assert.assertEquals(URIS.size(), entities.size());
   }
 
   @Test
@@ -168,6 +174,10 @@ public class CloudObjectInputSourceTest
 
     Assert.assertEquals(null, inputSource.getObjectGlob());
     Assert.assertEquals(URIS, returnedLocationUris);
+
+    final List<InputEntity> entities =
+        Lists.newArrayList(inputSource.getInputEntities(new JsonInputFormat(null, null, null, null, null)));
+    Assert.assertEquals(URIS.size(), entities.size());
   }
 
   @Test
@@ -190,6 +200,10 @@ public class CloudObjectInputSourceTest
 
     Assert.assertEquals("**.csv", inputSource.getObjectGlob());
     Assert.assertEquals(URIS, returnedLocationUris);
+
+    final List<InputEntity> entities =
+        Lists.newArrayList(inputSource.getInputEntities(new JsonInputFormat(null, null, null, null, null)));
+    Assert.assertEquals(OBJECTS.size(), entities.size());
   }
 
   @Test
@@ -208,8 +222,12 @@ public class CloudObjectInputSourceTest
 
     List<CloudObjectLocation> returnedLocations = splits.map(InputSplit::get).collect(Collectors.toList()).get(0);
 
-    Assert.assertEquals(null, inputSource.getObjectGlob());
+    Assert.assertNull(inputSource.getObjectGlob());
     Assert.assertEquals(OBJECTS, returnedLocations);
+
+    final List<InputEntity> entities =
+        Lists.newArrayList(inputSource.getInputEntities(new JsonInputFormat(null, null, null, null, null)));
+    Assert.assertEquals(OBJECTS.size(), entities.size());
   }
 
   @Test