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https://issues.apache.org/jira/browse/HIVE-27186?focusedWorklogId=858521&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-858521
]
ASF GitHub Bot logged work on HIVE-27186:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 21/Apr/23 23:31
Start Date: 21/Apr/23 23:31
Worklog Time Spent: 10m
Work Description: saihemanth-cloudera commented on code in PR #4194:
URL: https://github.com/apache/hive/pull/4194#discussion_r1174223446
##########
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/properties/SoftCache.java:
##########
@@ -0,0 +1,239 @@
+/*
+ * 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.hadoop.hive.metastore.properties;
+
+import java.lang.ref.SoftReference;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * A soft referenced cache.
+ * <p>
+ * The actual cache is held through a soft reference, allowing it to be GCed
under memory pressure.</p>
+ * <p>
+ * This class is <em>not</em> thread-safe.</p>
+ * @param <K> the cache key entry type
+ * @param <V> the cache key value type
+ */
+public class SoftCache<K, V> {
+ /** The default cache capacity. */
+ private static final int CACHE_CAPACITY = 64;
+ /** The default cache load factor. */
+ private static final float LOAD_FACTOR = 0.75f;
Review Comment:
Should we make this soft cache configurable? Do you see any downside by
doing so?
Issue Time Tracking
-------------------
Worklog Id: (was: 858521)
Time Spent: 6.5h (was: 6h 20m)
> A persistent property store
> ----------------------------
>
> Key: HIVE-27186
> URL: https://issues.apache.org/jira/browse/HIVE-27186
> Project: Hive
> Issue Type: Improvement
> Components: Metastore
> Affects Versions: 4.0.0-alpha-2
> Reporter: Henri Biestro
> Assignee: Henri Biestro
> Priority: Major
> Labels: pull-request-available
> Time Spent: 6.5h
> Remaining Estimate: 0h
>
> WHAT
> A persistent property store usable as a support facility for any metadata
> augmentation feature.
> WHY
> When adding new meta-data oriented features, we usually need to persist
> information linking the feature data and the HiveMetaStore objects it applies
> to. Any information related to a database, a table or the cluster - like
> statistics for example or any operational data state or data (think rolling
> backup) - fall in this use-case.
> Typically, accommodating such a feature requires modifying the Metastore
> database schema by adding or altering a table. It also usually implies
> modifying the thrift APIs to expose such meta-data to consumers.
> The proposed feature wants to solve the persistence and query/transport for
> these types of use-cases by exposing a 'key/(meta)value' store exposed as a
> property system.
> HOW
> A property-value model is the simple and generic exposed API.
> To provision for several usage scenarios, the model entry point is a
> 'namespace' that qualifies the feature-component property manager. For
> example, 'stats' could be the namespace for all properties related to the
> 'statistics' feature.
> The namespace identifies a manager that handles property-groups persisted as
> property-maps. For instance, all statistics pertaining to a given table would
> be collocated in the same property-group. As such, all properties (say number
> of 'unique_values' per columns) for a given HMS table 'relation0' would all
> be stored and persisted in the same property-map instance.
> Property-maps may be decorated by an (optional) schema that may declare the
> name and value-type of allowed properties (and their optional default value).
> Each property is addressed by a name, a path uniquely identifying the
> property in a given property map.
> The manager also handles transforming property-map names to the property-map
> keys used to persist them in the DB.
> The API provides inserting/updating properties in bulk transactionally. It
> also provides selection/projection to help reduce the volume of exchange
> between client/server; selection can use (JEXL expression) predicates to
> filter maps.
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