org.apache.cassandra.db.view

Class MaterializedView

java.lang.Object

org.apache.cassandra.db.view.MaterializedView

public class MaterializedView
extends java.lang.Object

A Materialized 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 MaterializedViewManager to ensure that if a view needs to be updated, the updates are properly created and fed into the view. This class does the job of translating the base row to the view row. It handles reading existing state and figuring out what tombstones need to be generated. createMutations below is the "main method"

Field Summary

Fields

Modifier and Type	Field and Description
java.lang.String	name

Constructor Summary

Constructors

Constructor and Description
MaterializedView(MaterializedViewDefinition definition, ColumnFamilyStore baseCfs)

Method Summary

Modifier and Type	Method and Description
void	build()
java.util.Collection<Mutation>	createMutations(java.nio.ByteBuffer key, AbstractBTreePartition partition, boolean isBuilding)
static CFMetaData	findBaseTable(java.lang.String keyspace, java.lang.String view)
static CFMetaData	getCFMetaData(MaterializedViewDefinition definition, CFMetaData baseCf, CFProperties properties)
ColumnFamilyStore	getViewCfs() Lazily fetch the CFS instance for the view.
boolean	updateAffectsView(AbstractBTreePartition partition) Check to see if the update could possibly modify a view.
boolean	updateDefinition(MaterializedViewDefinition definition) This updates the columns stored which are dependent on the base CFMetaData.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

name

public final java.lang.String name

Constructor Detail

MaterializedView

public MaterializedView(MaterializedViewDefinition definition,
                        ColumnFamilyStore baseCfs)

Method Detail

getViewCfs

public ColumnFamilyStore getViewCfs()

Lazily fetch the CFS instance for the view. We do this lazily to avoid initilization issues.

Returns:

The views CFS instance

updateDefinition

public boolean updateDefinition(MaterializedViewDefinition definition)

This updates the columns stored which are dependent on the base CFMetaData.

Returns:

true if the view contains only columns which are part of the base's primary key; false if there is at least one column which is not.

updateAffectsView

public boolean updateAffectsView(AbstractBTreePartition partition)

Check to see if the update could possibly modify a view. Cases where the view may be updated are:

• View selects all columns
• Update contains any range tombstones
• Update touches one of the columns included in the view

If the update contains any range tombstones, there is a possibility that it will not touch a range that is currently included in the view.

Returns:

true if modifies a column included in the view

createMutations

public java.util.Collection<Mutation> createMutations(java.nio.ByteBuffer key,
                                                      AbstractBTreePartition partition,
                                                      boolean isBuilding)

Parameters:

isBuilding - If the view is currently being built, we do not query the values which are already stored, since all of the update will already be present in the base table.

Returns:

View mutations which represent the changes necessary as long as previously created mutations for the view have been applied successfully. This is based solely on the changes that are necessary given the current state of the base table and the newly applying partition data.

build

public void build()

findBaseTable

@Nullable
public static CFMetaData findBaseTable(java.lang.String keyspace,
                                                 java.lang.String view)

getCFMetaData

public static CFMetaData getCFMetaData(MaterializedViewDefinition definition,
                                       CFMetaData baseCf,
                                       CFProperties properties)

Returns:

CFMetaData which represents the definition given