Github user ericl commented on a diff in the pull request:
https://github.com/apache/spark/pull/15539#discussion_r84352402
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileStatusCache.scala
---
@@ -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.spark.sql.execution.datasources
+
+import java.util.concurrent.ConcurrentHashMap
+
+import org.apache.hadoop.fs.{FileStatus, Path}
+
+import org.apache.spark.metrics.source.HiveCatalogMetrics
+import org.apache.spark.util.SerializableConfiguration
+
+/**
+ * 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 {
--- End diff --
This is already better than what we have in 2.0 - which is caching
everything with no limit.
I think a global cache is really fairly complicated since we can no longer
rely on the Java GC to manage the lifetime of the cache entries. Unless we want
to do cache GC in a finalizer, I don't think this is worth it.
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