Package org.apache.druid.segment.join

Class JoinableClause

java.lang.Object

org.apache.druid.segment.join.JoinableClause

All Implemented Interfaces:

ReferenceCountedObjectProvider<Closeable>

public class JoinableClause
extends Object
implements ReferenceCountedObjectProvider<Closeable>

Represents everything about a join clause except for the left-hand datasource. In other words, if the full join clause is "t1 JOIN t2 ON t1.x = t2.x" then this class represents "JOIN t2 ON x = t2.x" -- it does not include references to the left-hand "t1".

Created from PreJoinableClause.

Constructor Summary

Constructors

Constructor	Description
JoinableClause(String prefix, Joinable joinable, JoinType joinType, JoinConditionAnalysis condition)

Method Summary

Modifier and Type	Method	Description
Optional<Closeable>	acquireReference()	This method increments a reference count and provides a Closeable that decrements the reference count when closed.
boolean	equals(Object o)
List<String>	getAvailableColumnsPrefixed()	Returns a list of columns from the underlying Joinable.getAvailableColumns() method, with our prefix (getPrefix()) prepended.
JoinConditionAnalysis	getCondition()	The join condition.
Joinable	getJoinable()	The right-hand Joinable.
JoinType	getJoinType()	The type of join: LEFT, RIGHT, INNER, or FULL.
String	getPrefix()	The prefix to apply to all columns from the Joinable.
int	hashCode()
boolean	includesColumn(String columnName)	Returns whether "columnName" can be retrieved from the Joinable represented by this clause (i.e., whether it starts with prefix and has at least one other character beyond that).
String	toString()
String	unprefix(String columnName)	Removes our prefix from "columnName".

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

JoinableClause

public JoinableClause(String prefix,
 Joinable joinable,
 JoinType joinType,
 JoinConditionAnalysis condition)

Method Details

getPrefix

public String getPrefix()

The prefix to apply to all columns from the Joinable. The idea is that during a join, any columns that start with this prefix should be retrieved from our Joinable's JoinMatcher.getColumnSelectorFactory(). Any other columns should be returned from the left-hand side of the join. The prefix can be any string, as long as it is nonempty and not itself a prefix of the reserved column name __time.

See Also:

• the list of columns from our Joinable with prefixes attached
• a method for removing prefixes

getJoinable

public Joinable getJoinable()

The right-hand Joinable.

getJoinType

public JoinType getJoinType()

The type of join: LEFT, RIGHT, INNER, or FULL.

getCondition

public JoinConditionAnalysis getCondition()

The join condition. When referring to right-hand columns, it should include the prefix.

getAvailableColumnsPrefixed

public List<String> getAvailableColumnsPrefixed()

Returns a list of columns from the underlying Joinable.getAvailableColumns() method, with our prefix (getPrefix()) prepended.

includesColumn

public boolean includesColumn(String columnName)

Returns whether "columnName" can be retrieved from the Joinable represented by this clause (i.e., whether it starts with prefix and has at least one other character beyond that).

unprefix

public String unprefix(String columnName)

Removes our prefix from "columnName". Must only be called if includesColumn(java.lang.String) would have returned true on this column name.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

acquireReference

public Optional<Closeable> acquireReference()

Description copied from interface: ReferenceCountedObjectProvider

This method increments a reference count and provides a Closeable that decrements the reference count when closed. The object returned by this method may or may not be thread-safe, it is best to check with the implementation.

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 ideally avoid allowing this method to throw exceptions, but callers are responsible for closing the returned object should any operations on it throw exceptions.

For callers: if this method returns non-empty, IT MUST BE CLOSED, else reference counts can potentially leak.

Specified by:

acquireReference in interface ReferenceCountedObjectProvider<Closeable>