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Subject [GitHub] [cassandra] dvohra commented on a change in pull request #402: New/virtualtables
Date Fri, 14 Feb 2020 18:02:42 GMT
dvohra commented on a change in pull request #402: New/virtualtables

 File path: doc/source/new/virtualtables.rst
 @@ -0,0 +1,586 @@
+.. 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
+.. Unless required by applicable law or agreed to in writing, software
+.. distributed under the License is distributed on an "AS IS" BASIS,
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+.. See the License for the specific language governing permissions and
+.. limitations under the License.
+Virtual Tables
+Apache Cassandra 4.0 implements virtual tables (`CASSANDRA-7622
+A virtual table is a table that is backed by an API instead of data explicitly managed and
stored as SSTables. Apache Cassandra 4.0 implements a virtual keyspace interface for virtual
tables. Virtual tables are specific to each node. 
+A virtual table could have several uses including:
+- Expose JMX data/metrics through CQL
+- Expose YAML configuration information
+- Expose other MBean data
+How  are Virtual Tables different from regular tables?
+Virtual tables and virtual keyspaces are quite different from regular tables and keyspaces
respectively such as:
+- Virtual tables are read-only 
+- Virtual tables are not replicated
+- Virtual tables have no associated SSTables
+- Consistency level of the queries sent virtual tables are ignored
+- Virtual tables are managed by Cassandra and a user cannot run  DDL to create new virtual
tables or DML to modify existing virtual tables
+- Virtual tables are created in special keyspaces and not just any keyspace
+- All existing virtual tables use LocalPartitioner
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