org.apache.cassandra.db.view

Class View

java.lang.Object

org.apache.cassandra.db.view.View

public class View
extends java.lang.Object

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 ViewManager 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(AbstractBTreePartition, TemporalRow.Set, boolean) is the "main method"

Field Summary

Fields

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

Constructor Summary

Constructors

Constructor and Description
View(ViewDefinition definition, ColumnFamilyStore baseCfs)

Method Summary

Modifier and Type	Method and Description
void	build()
static java.lang.String	buildSelectStatement(java.lang.String cfName, java.util.Collection<ColumnDefinition> includedColumns, java.lang.String whereClause) Builds the string text for a materialized view's SELECT statement.
java.util.Collection<Mutation>	createMutations(AbstractBTreePartition partition, org.apache.cassandra.db.view.TemporalRow.Set rowSet, boolean isBuilding)
static java.lang.Iterable<ViewDefinition>	findAll(java.lang.String keyspace, java.lang.String baseTable)
static CFMetaData	findBaseTable(java.lang.String keyspace, java.lang.String viewName)
ViewDefinition	getDefinition()
ReadQuery	getReadQuery() Returns the ReadQuery used to filter this view.
SelectStatement	getSelectStatement() Returns the SelectStatement used to populate and filter this view.
org.apache.cassandra.db.view.TemporalRow.Set	getTemporalRowSet(AbstractBTreePartition partition, org.apache.cassandra.db.view.TemporalRow.Set existing, boolean isBuilding) Splits the partition update up and adds the existing state to each row.
static java.lang.String	relationsToWhereClause(java.util.List<Relation> whereClause)
boolean	updateAffectsView(AbstractBTreePartition partition) Check to see if the update could possibly modify a view.
boolean	updateDefinition(ViewDefinition 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

View

public View(ViewDefinition definition,
            ColumnFamilyStore baseCfs)

Method Detail

getDefinition

public ViewDefinition getDefinition()

updateDefinition

public boolean updateDefinition(ViewDefinition 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

getTemporalRowSet

public org.apache.cassandra.db.view.TemporalRow.Set getTemporalRowSet(AbstractBTreePartition partition,
                                                                      org.apache.cassandra.db.view.TemporalRow.Set existing,
                                                                      boolean isBuilding)

Splits the partition update up and adds the existing state to each row. This data can be reused for multiple MV updates on the same base table

Parameters:

partition - the mutation

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:

The set of temoral rows contained in this update

getSelectStatement

public SelectStatement getSelectStatement()

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.

getReadQuery

public ReadQuery getReadQuery()

Returns the ReadQuery used to filter this view. Internal users should access the query this way to ensure it has been prepared.

createMutations

public java.util.Collection<Mutation> createMutations(AbstractBTreePartition partition,
                                                      org.apache.cassandra.db.view.TemporalRow.Set rowSet,
                                                      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 viewName)

findAll

public static java.lang.Iterable<ViewDefinition> findAll(java.lang.String keyspace,
                                                         java.lang.String baseTable)

buildSelectStatement

public static java.lang.String buildSelectStatement(java.lang.String cfName,
                                                    java.util.Collection<ColumnDefinition> includedColumns,
                                                    java.lang.String whereClause)

Builds the string text for a materialized view's SELECT statement.

relationsToWhereClause

public static java.lang.String relationsToWhereClause(java.util.List<Relation> whereClause)