Package org.apache.druid.segment.join

Class JoinConditionAnalysis

java.lang.Object

org.apache.druid.segment.join.JoinConditionAnalysis

public class JoinConditionAnalysis
extends Object

Represents analysis of a join condition. Each condition is decomposed into "equiConditions" and "nonEquiConditions". 1) The equiConditions are of the form ExpressionOfLeft = ColumnFromRight. The right-hand part cannot be an expression because we use this analysis to determine if we can perform the join using hashtables built off right-hand-side columns. 2) The nonEquiConditions are other conditions that should also be ANDed together All of these conditions are ANDed together to get the overall condition.

Method Summary

Modifier and Type	Method	Description
boolean	canHashJoin()	Returns whether this condition can be satisfied using a hashtable made from the right-hand side.
boolean	equals(Object o)
static JoinConditionAnalysis	forExpression(String condition, String rightPrefix, ExprMacroTable macroTable)	Analyze a join condition.
static JoinConditionAnalysis	forExpression(String condition, Expr conditionExpr, String rightPrefix)	Analyze a join condition from a pre-parsed expression.
List<Equality>	getEquiConditions()	Return a list of equi-conditions (see class-level javadoc).
List<Expr>	getNonEquiConditions()	Return a list of non-equi-conditions (see class-level javadoc).
String	getOriginalExpression()	Return the condition expression.
Set<String>	getRequiredColumns()	Returns the set of column names required by this join condition.
Set<String>	getRightEquiConditionKeys()	Returns the distinct column keys from the RHS required to evaluate the equi conditions.
int	hashCode()
boolean	isAlwaysFalse()	Return whether this condition is a constant that is always false.
boolean	isAlwaysTrue()	Return whether this condition is a constant that is always true.
String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

forExpression

public static JoinConditionAnalysis forExpression(String condition,
                                                  String rightPrefix,
                                                  ExprMacroTable macroTable)

Analyze a join condition.

Parameters:

condition - the condition expression

rightPrefix - prefix for the right-hand side of the join; will be used to determine which identifiers in the condition come from the right-hand side and which come from the left-hand side

macroTable - macro table for parsing the condition expression

forExpression

public static JoinConditionAnalysis forExpression(String condition,
                                                  Expr conditionExpr,
                                                  String rightPrefix)

Analyze a join condition from a pre-parsed expression.

Parameters:

condition - the condition expression

conditionExpr - the parsed condition expression. Must match "condition".

rightPrefix - prefix for the right-hand side of the join; will be used to determine which identifiers in the condition come from the right-hand side and which come from the left-hand side

getOriginalExpression

public String getOriginalExpression()

Return the condition expression.

getEquiConditions

public List<Equality> getEquiConditions()

Return a list of equi-conditions (see class-level javadoc).

getNonEquiConditions

public List<Expr> getNonEquiConditions()

Return a list of non-equi-conditions (see class-level javadoc).

isAlwaysFalse

public boolean isAlwaysFalse()

Return whether this condition is a constant that is always false.

isAlwaysTrue

public boolean isAlwaysTrue()

Return whether this condition is a constant that is always true.

canHashJoin

public boolean canHashJoin()

Returns whether this condition can be satisfied using a hashtable made from the right-hand side.

getRightEquiConditionKeys

public Set<String> getRightEquiConditionKeys()

Returns the distinct column keys from the RHS required to evaluate the equi conditions.

getRequiredColumns

public Set<String> getRequiredColumns()

Returns the set of column names required by this join condition. Columns from the right-hand side are returned with their prefixes included.

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