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/*
* 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.view;
import java.util.*;
import java.util.stream.Collectors;
import javax.annotation.Nullable;
import com.google.common.collect.Iterables;
import org.apache.cassandra.cql3.*;
import org.apache.cassandra.cql3.selection.RawSelector;
import org.apache.cassandra.cql3.selection.Selectable;
import org.apache.cassandra.cql3.statements.SelectStatement;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.rows.*;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.KeyspaceMetadata;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.schema.TableMetadataRef;
import org.apache.cassandra.schema.ViewMetadata;
import org.apache.cassandra.service.ClientState;
import org.apache.cassandra.utils.FBUtilities;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A View copies data from a base table into a view table which can be queried independently from the
* base. Every update which targets the base table must be fed through the {@link ViewManager} to ensure
* that if a view needs to be updated, the updates are properly created and fed into the view.
*/
public class View
{
public final static String USAGE_WARNING = "Materialized views are experimental and are not recommended for production use.";
private static final Logger logger = LoggerFactory.getLogger(View.class);
public final String name;
private volatile ViewMetadata definition;
private final ColumnFamilyStore baseCfs;
public volatile List baseNonPKColumnsInViewPK;
private ViewBuilder builder;
private SelectStatement select;
private ReadQuery query;
public View(ViewMetadata definition, ColumnFamilyStore baseCfs)
{
this.baseCfs = baseCfs;
this.name = definition.name();
updateDefinition(definition);
}
public ViewMetadata getDefinition()
{
return definition;
}
/**
* This updates the columns stored which are dependent on the base TableMetadata.
*/
public void updateDefinition(ViewMetadata definition)
{
this.definition = definition;
List nonPKDefPartOfViewPK = new ArrayList<>();
for (ColumnMetadata baseColumn : baseCfs.metadata.get().columns())
{
ColumnMetadata viewColumn = getViewColumn(baseColumn);
if (viewColumn != null && !baseColumn.isPrimaryKeyColumn() && viewColumn.isPrimaryKeyColumn())
nonPKDefPartOfViewPK.add(baseColumn);
}
this.baseNonPKColumnsInViewPK = nonPKDefPartOfViewPK;
}
/**
* The view column corresponding to the provided base column. This can
* return {@code null} if the column is denormalized in the view.
*/
public ColumnMetadata getViewColumn(ColumnMetadata baseColumn)
{
return definition.metadata.getColumn(baseColumn.name);
}
/**
* The base column corresponding to the provided view column. This should
* never return {@code null} since a view can't have its "own" columns.
*/
public ColumnMetadata getBaseColumn(ColumnMetadata viewColumn)
{
ColumnMetadata baseColumn = baseCfs.metadata().getColumn(viewColumn.name);
assert baseColumn != null;
return baseColumn;
}
/**
* Whether the view might be affected by the provided update.
*
* Note that having this method return {@code true} is not an absolute guarantee that the view will be
* updated, just that it most likely will, but a {@code false} return guarantees it won't be affected).
*
* @param partitionKey the partition key that is updated.
* @param update the update being applied.
* @return {@code false} if we can guarantee that inserting {@code update} for key {@code partitionKey}
* won't affect the view in any way, {@code true} otherwise.
*/
public boolean mayBeAffectedBy(DecoratedKey partitionKey, Row update)
{
// We can guarantee that the view won't be affected if:
// - the clustering is excluded by the view filter (note that this isn't true of the filter on regular columns:
// even if an update don't match a view condition on a regular column, that update can still invalidate an pre-existing
// entry).
// - or the update don't modify any of the columns impacting the view (where "impacting" the view means that column is
// neither included in the view, nor used by the view filter).
if (!getReadQuery().selectsClustering(partitionKey, update.clustering()))
return false;
return true;
}
/**
* Whether a given base row matches the view filter (and thus if is should have a corresponding entry).
*
* Note that this differs from {@link #mayBeAffectedBy} in that the provide row must be the current
* state of the base row, not just some updates to it. This method also has no false positive: a base
* row either do or don't match the view filter.
*
* @param partitionKey the partition key that is updated.
* @param baseRow the current state of a particular base row.
* @param nowInSec the current time in seconds (to decide what is live and what isn't).
* @return {@code true} if {@code baseRow} matches the view filters, {@code false} otherwise.
*/
public boolean matchesViewFilter(DecoratedKey partitionKey, Row baseRow, long nowInSec)
{
return getReadQuery().selectsClustering(partitionKey, baseRow.clustering())
&& getSelectStatement().rowFilterForInternalCalls().isSatisfiedBy(baseCfs.metadata(), partitionKey, baseRow, nowInSec);
}
/**
* Returns the SelectStatement used to populate and filter this view. Internal users should access the select
* statement this way to ensure it has been prepared.
*/
SelectStatement getSelectStatement()
{
if (null == select)
{
SelectStatement.Parameters parameters =
new SelectStatement.Parameters(Collections.emptyList(),
Collections.emptyList(),
false,
true,
false);
SelectStatement.RawStatement rawSelect =
new SelectStatement.RawStatement(new QualifiedName(baseCfs.getKeyspaceName(), baseCfs.name),
parameters,
selectClause(),
definition.whereClause,
null,
null);
rawSelect.setBindVariables(Collections.emptyList());
select = rawSelect.prepare(ClientState.forInternalCalls(), true);
}
return select;
}
private List selectClause()
{
return definition.metadata
.columns()
.stream()
.map(c -> c.name.toString())
.map(Selectable.RawIdentifier::forQuoted)
.map(c -> new RawSelector(c, null))
.collect(Collectors.toList());
}
/**
* Returns the ReadQuery used to filter this view. Internal users should access the query this way to ensure it
* has been prepared.
*/
ReadQuery getReadQuery()
{
if (query == null)
query = getSelectStatement().getQuery(QueryOptions.forInternalCalls(Collections.emptyList()), FBUtilities.nowInSeconds());
return query;
}
public synchronized void build()
{
stopBuild();
builder = new ViewBuilder(baseCfs, this);
builder.start();
}
/**
* Stops the building of this view, no-op if it isn't building.
*/
synchronized void stopBuild()
{
if (builder != null)
{
logger.debug("Stopping current view builder due to schema change or truncate");
builder.stop();
builder = null;
}
}
@Nullable
public static TableMetadataRef findBaseTable(String keyspace, String viewName)
{
ViewMetadata view = Schema.instance.getView(keyspace, viewName);
return (view == null) ? null : Schema.instance.getTableMetadataRef(view.baseTableId);
}
// TODO: REMOVE
public static Iterable findAll(String keyspace, String baseTable)
{
KeyspaceMetadata ksm = Schema.instance.getKeyspaceMetadata(keyspace);
return Iterables.filter(ksm.views, view -> view.baseTableName.equals(baseTable));
}
public boolean hasSamePrimaryKeyColumnsAsBaseTable()
{
return baseNonPKColumnsInViewPK.isEmpty();
}
/**
* When views contains a primary key column that is not part
* of the base table primary key, we use that column liveness
* info as the view PK, to ensure that whenever that column
* is not live in the base, the row is not live in the view.
*
* This is done to prevent cells other than the view PK from
* making the view row alive when the view PK column is not
* live in the base. So in this case we tie the row liveness,
* to the primary key liveness.
*
* See CASSANDRA-11500 for context.
*/
public boolean enforceStrictLiveness()
{
return !baseNonPKColumnsInViewPK.isEmpty();
}
}