org.apache.druid.segment.join.lookup

Class LookupJoinable

java.lang.Object

org.apache.druid.segment.join.lookup.LookupJoinable

All Implemented Interfaces:

Joinable, ReferenceCountedObject

public class LookupJoinable
extends Object
implements Joinable

Field Summary

Fields inherited from interface org.apache.druid.segment.join.Joinable

CARDINALITY_UNKNOWN

Method Summary

Modifier and Type	Method and Description
Optional<Closeable>	acquireReferences() This method is expected to increment a reference count and provide a Closeable that decrements the reference count when closed.
List<String>	getAvailableColumns() Returns the list of columns that this Joinable offers.
int	getCardinality(String columnName) Returns the cardinality of "columnName", or Joinable.CARDINALITY_UNKNOWN if not known.
ColumnCapabilities	getColumnCapabilities(String columnName) Returns capabilities for one of this Joinable's columns.
Optional<Set<String>>	getCorrelatedColumnValues(String searchColumnName, String searchColumnValue, String retrievalColumnName, long maxCorrelationSetSize, boolean allowNonKeyColumnSearch) Searches a column from this Joinable for a particular value, finds rows that match, and returns values of a second column for those rows.
JoinMatcher	makeJoinMatcher(ColumnSelectorFactory leftSelectorFactory, JoinConditionAnalysis condition, boolean remainderNeeded) Creates a JoinMatcher that can be used to implement a join onto this Joinable.
static LookupJoinable	wrap(LookupExtractor extractor)

Methods inherited from class java.lang.Object

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

Method Detail

wrap

public static LookupJoinable wrap(LookupExtractor extractor)

getAvailableColumns

public List<String> getAvailableColumns()

Description copied from interface: Joinable

Returns the list of columns that this Joinable offers.

Specified by:

getAvailableColumns in interface Joinable

getCardinality

public int getCardinality(String columnName)

Description copied from interface: Joinable

Returns the cardinality of "columnName", or Joinable.CARDINALITY_UNKNOWN if not known. May be used at query time to trigger optimizations. If not Joinable.CARDINALITY_UNKNOWN, this must match the cardinality of selectors returned by the ColumnSelectorFactory.makeDimensionSelector(org.apache.druid.query.dimension.DimensionSpec) method of this joinable's JoinMatcher.getColumnSelectorFactory() .

Specified by:

getCardinality in interface Joinable

getColumnCapabilities

@Nullable
public ColumnCapabilities getColumnCapabilities(String columnName)

Description copied from interface: Joinable

Returns capabilities for one of this Joinable's columns.

Specified by:

getColumnCapabilities in interface Joinable

Parameters:

columnName - column name

Returns:

capabilities, or null if the columnName is not one of this Joinable's columns

makeJoinMatcher

public JoinMatcher makeJoinMatcher(ColumnSelectorFactory leftSelectorFactory,
                                   JoinConditionAnalysis condition,
                                   boolean remainderNeeded)

Description copied from interface: Joinable

Creates a JoinMatcher that can be used to implement a join onto this Joinable.

Specified by:

makeJoinMatcher in interface Joinable

Parameters:

leftSelectorFactory - column selector factory that allows access to the left-hand side of the join

condition - join condition for the matcher

remainderNeeded - whether or not JoinMatcher.matchRemainder() will ever be called on the matcher. If we know it will not, additional optimizations are often possible.

Returns:

the matcher

getCorrelatedColumnValues

public Optional<Set<String>> getCorrelatedColumnValues(String searchColumnName,
                                                       String searchColumnValue,
                                                       String retrievalColumnName,
                                                       long maxCorrelationSetSize,
                                                       boolean allowNonKeyColumnSearch)

Description copied from interface: Joinable

Searches a column from this Joinable for a particular value, finds rows that match, and returns values of a second column for those rows.

Specified by:

getCorrelatedColumnValues in interface Joinable

Parameters:

searchColumnName - Name of the search column. This is the column that is being used in the filter

searchColumnValue - Target value of the search column. This is the value that is being filtered on.

retrievalColumnName - The column to retrieve values from. This is the column that is being joined against.

maxCorrelationSetSize - Maximum number of values to retrieve. If we detect that more values would be returned than this limit, return an empty set.

allowNonKeyColumnSearch - If true, allow searchs on non-key columns. If this is false, a search on a non-key column should return an empty set.

Returns:

The set of correlated column values. If we cannot determine correlated values, return absent. In case either the search or retrieval column names are not found, this will return absent.

acquireReferences

public Optional<Closeable> acquireReferences()

Description copied from interface: ReferenceCountedObject

This method is expected to increment a reference count and provide a Closeable that decrements the reference count when closed. This is likely just a wrapper around ReferenceCountingCloseableObject.incrementReferenceAndDecrementOnceCloseable(), but may also include any other associated references which should be incremented when this method is called, and decremented/released by the closeable. IMPORTANT NOTE: to fulfill the contract of this method, implementors must return a closeable to indicate that the reference can be acquired, even if there is nothing to close. Implementors should avoid allowing this method or the Closeable it creates to throw exceptions. For callers: if this method returns non-empty, IT MUST BE CLOSED, else reference counts can potentially leak.

Specified by:

acquireReferences in interface ReferenceCountedObject