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.

Field Summary

Fields

Modifier and Type	Field and Description
java.util.List<ColumnDefinition>	baseNonPKColumnsInViewPK
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.
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)
ColumnDefinition	getBaseColumn(ColumnDefinition viewColumn) The base column corresponding to the provided view column.
ViewDefinition	getDefinition()
ReadQuery	getReadQuery() Returns the ReadQuery used to filter this view.
SelectStatement	getSelectStatement() Returns the SelectStatement used to populate and filter this view.
ColumnDefinition	getViewColumn(ColumnDefinition baseColumn) The view column corresponding to the provided base column.
boolean	matchesViewFilter(DecoratedKey partitionKey, Row baseRow, int nowInSec) Whether a given base row matches the view filter (and thus if is should have a corresponding entry).
boolean	mayBeAffectedBy(DecoratedKey partitionKey, Row update) Whether the view might be affected by the provided update.
static java.lang.String	relationsToWhereClause(java.util.List<Relation> whereClause)
void	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

baseNonPKColumnsInViewPK

public volatile java.util.List<ColumnDefinition> baseNonPKColumnsInViewPK

Constructor Detail

View

public View(ViewDefinition definition,
            ColumnFamilyStore baseCfs)

Method Detail

getDefinition

public ViewDefinition getDefinition()

updateDefinition

public void updateDefinition(ViewDefinition definition)

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

getViewColumn

public ColumnDefinition getViewColumn(ColumnDefinition baseColumn)

The view column corresponding to the provided base column. This can return null if the column is denormalized in the view.

getBaseColumn

public ColumnDefinition getBaseColumn(ColumnDefinition viewColumn)

The base column corresponding to the provided view column. This should never return null since a view can't have its "own" columns.

mayBeAffectedBy

public boolean mayBeAffectedBy(DecoratedKey partitionKey,
                               Row update)

Whether the view might be affected by the provided update.

Note that having this method return true is not an absolute guarantee that the view will be updated, just that it most likely will, but a false return guarantees it won't be affected).

Parameters:

partitionKey - the partition key that is updated.

update - the update being applied.

Returns:

false if we can guarantee that inserting update for key partitionKey won't affect the view in any way, true otherwise.

matchesViewFilter

public boolean matchesViewFilter(DecoratedKey partitionKey,
                                 Row baseRow,
                                 int nowInSec)

Whether a given base row matches the view filter (and thus if is should have a corresponding entry).

Note that this differs from mayBeAffectedBy(org.apache.cassandra.db.DecoratedKey, org.apache.cassandra.db.rows.Row) 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.

Parameters:

partitionKey - the partition key that is updated.

baseRow - the current state of a particular base row.

nowInSec - the current time in seconds (to decide what is live and what isn't).

Returns:

true if baseRow matches the view filters, false otherwise.

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.

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)