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<ColumnMetadata>	baseNonPKColumnsInViewPK
java.lang.String	name
static java.lang.String	USAGE_WARNING

Constructor Summary

Constructors

Constructor and Description
View(ViewMetadata definition, ColumnFamilyStore baseCfs)

Method Summary

Modifier and Type	Method and Description
void	build()
boolean	enforceStrictLiveness() 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.
static java.lang.Iterable<ViewMetadata>	findAll(java.lang.String keyspace, java.lang.String baseTable)
static TableMetadataRef	findBaseTable(java.lang.String keyspace, java.lang.String viewName)
ColumnMetadata	getBaseColumn(ColumnMetadata viewColumn) The base column corresponding to the provided view column.
ViewMetadata	getDefinition()
ColumnMetadata	getViewColumn(ColumnMetadata baseColumn) The view column corresponding to the provided base column.
boolean	hasSamePrimaryKeyColumnsAsBaseTable()
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.
void	updateDefinition(ViewMetadata definition) This updates the columns stored which are dependent on the base TableMetadata.

Methods inherited from class java.lang.Object

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

Field Detail

USAGE_WARNING

public static final java.lang.String USAGE_WARNING

See Also:

Constant Field Values

name

public final java.lang.String name

baseNonPKColumnsInViewPK

public volatile java.util.List<ColumnMetadata> baseNonPKColumnsInViewPK

Constructor Detail

View

public View(ViewMetadata definition,
            ColumnFamilyStore baseCfs)

Method Detail

getDefinition

public ViewMetadata getDefinition()

updateDefinition

public void updateDefinition(ViewMetadata definition)

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

getViewColumn

public ColumnMetadata getViewColumn(ColumnMetadata baseColumn)

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

getBaseColumn

public ColumnMetadata getBaseColumn(ColumnMetadata 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.

build

public void build()

findBaseTable

@Nullable
public static TableMetadataRef findBaseTable(java.lang.String keyspace,
                                                       java.lang.String viewName)

findAll

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

hasSamePrimaryKeyColumnsAsBaseTable

public boolean hasSamePrimaryKeyColumnsAsBaseTable()

enforceStrictLiveness

public boolean enforceStrictLiveness()

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.