Github user ericl commented on a diff in the pull request:
https://github.com/apache/spark/pull/15539#discussion_r84424682
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileStatusCache.scala
---
@@ -0,0 +1,149 @@
+/*
+ * 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.spark.sql.execution.datasources
+
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.atomic.AtomicBoolean
+
+import scala.collection.JavaConverters._
+
+import com.google.common.cache._
+import org.apache.hadoop.fs.{FileStatus, Path}
+
+import org.apache.spark.internal.Logging
+import org.apache.spark.metrics.source.HiveCatalogMetrics
+import org.apache.spark.sql.SparkSession
+import org.apache.spark.util.{SerializableConfiguration, SizeEstimator}
+
+/**
+ * A cache of the leaf files of partition directories. We cache these
files in order to speed
+ * up iterated queries over the same set of partitions. Otherwise, each
query would have to
+ * hit remote storage in order to gather file statistics for physical
planning.
+ *
+ * Each resolved catalog table has its own FileStatusCache. When the
backing relation for the
+ * table is refreshed via refreshTable() or refreshByPath(), this cache
will be invalidated.
+ */
+abstract class FileStatusCache {
+ /**
+ * @return the leaf files for the specified path from this cache, or
None if not cached.
+ */
+ def getLeafFiles(path: Path): Option[Array[FileStatus]] = None
+
+ /**
+ * Saves the given set of leaf files for a path in this cache.
+ */
+ def putLeafFiles(path: Path, leafFiles: Array[FileStatus]): Unit
+
+ /**
+ * Invalidates all data held by this cache.
+ */
+ def invalidateAll(): Unit
+}
+
+object FileStatusCache {
+ // Opaque object that uniquely identifies a shared cache user
+ type ClientId = Object
--- End diff --
I think it's better to err on the side of isolation here. Otherwise, it is
harder to reason about what is actually invalidated when a table is refreshed.
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