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https://issues.apache.org/jira/browse/CASSANDRA-7622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16396174#comment-16396174
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ASF GitHub Bot commented on CASSANDRA-7622:
-------------------------------------------
Github user zznate commented on a diff in the pull request:
https://github.com/apache/cassandra/pull/205#discussion_r173962979
--- Diff: src/java/org/apache/cassandra/db/VirtualTable.java ---
@@ -0,0 +1,148 @@
+/*
+ * 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.cassandra.db;
+
+import static java.lang.String.format;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.List;
+
+import org.apache.cassandra.cql3.Operation;
+import org.apache.cassandra.cql3.QueryOptions;
+import org.apache.cassandra.cql3.UpdateParameters;
+import org.apache.cassandra.cql3.statements.SelectStatement;
+import org.apache.cassandra.db.filter.DataLimits;
+import org.apache.cassandra.db.partitions.PartitionUpdate;
+import org.apache.cassandra.db.rows.Row;
+import org.apache.cassandra.exceptions.CassandraException;
+import org.apache.cassandra.exceptions.ConfigurationException;
+import org.apache.cassandra.exceptions.InvalidRequestException;
+import org.apache.cassandra.schema.TableMetadata;
+import org.apache.cassandra.transport.messages.ResultMessage;
+import org.apache.cassandra.utils.FBUtilities;
+
+import com.google.common.collect.Lists;
+
+/**
+ * Base requirements for a VirtualTable. This is required to provide
metadata about the virtual table, such as the
+ * partition and clustering keys, and provide a ReadQuery for a
SelectStatement.
+ */
+public abstract class VirtualTable
+{
+ protected final TableMetadata metadata;
+ protected String keyspace;
+ protected String name;
+
+ public VirtualTable(TableMetadata metadata)
+ {
+ this.metadata = metadata;
+ }
+
+ public String getTableName()
+ {
+ return this.metadata.name;
+ }
+
+ /**
+ * Is this table writable?
+ *
+ * @return True if UPDATE is supported
+ */
+ public boolean writable()
+ {
+ return false;
+ }
+
+ /**
+ * If the table allows unrestricted queries (ie filter on clustering
key with no partition). Since These tables are
+ * not backed by the C* data model, this restriction isnt always
necessary.
+ */
+ public boolean allowFiltering()
+ {
+ return true;
+ }
+
+ /**
+ * Return some implementation of a ReadQuery for a given select
statement and query options.
+ *
+ * @param selectStatement
+ * @param options
+ * @param limits
+ * @param nowInSec
+ * @return ReadQuery
+ */
+ public abstract ReadQuery getQuery(SelectStatement selectStatement,
QueryOptions options, DataLimits limits,
+ int nowInSec);
+
+ /**
+ * Execute an update operation.
+ *
+ * @param partitionKey
+ * partition key for the update.
+ * @param params
+ * parameters of the update.
+ */
+ public void mutate(DecoratedKey partitionKey, Row row) throws
CassandraException
+ {
+ // this should not be called unless writable is overridden
+ throw new InvalidRequestException("Not Implemented");
+ }
+
+ public static Class<? extends VirtualTable> classFromName(String name)
+ {
+ String className = name.contains(".")
+ ? name
+ : "org.apache.cassandra.db.virtual." + name;
+ Class<VirtualTable> strategyClass =
FBUtilities.classForName(className, "virtual table");
+
+ if (!VirtualTable.class.isAssignableFrom(strategyClass))
+ {
+ throw new ConfigurationException(format("Compaction strategy
class %s is not derived from VirtualTable",
+ className));
+ }
+
+ return strategyClass;
+ }
+
+ public static Key createKey()
+ {
+ return new Key();
--- End diff --
Does it make sense to allow empty key creation as API? If not, switch it to
a builder so's it can be validated.
> Implement virtual tables
> ------------------------
>
> Key: CASSANDRA-7622
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7622
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Tupshin Harper
> Assignee: Chris Lohfink
> Priority: Major
> Fix For: 4.x
>
>
> There are a variety of reasons to want virtual tables, which would be any
> table that would be backed by an API, rather than data explicitly managed and
> stored as sstables.
> One possible use case would be to expose JMX data through CQL as a
> resurrection of CASSANDRA-3527.
> Another is a more general framework to implement the ability to expose yaml
> configuration information. So it would be an alternate approach to
> CASSANDRA-7370.
> A possible implementation would be in terms of CASSANDRA-7443, but I am not
> presupposing.
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