Package io.trino.sql.planner

Class EqualityInference

java.lang.Object

io.trino.sql.planner.EqualityInference

public class EqualityInference
extends Object

Makes equality based inferences to rewrite Expressions and generate equality sets in terms of specified symbol scopes

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	EqualityInference.EqualityPartition

Method Summary

Modifier and Type	Method	Description
EqualityInference.EqualityPartition	generateEqualitiesPartitionedBy(Set<Symbol> scope)	Dumps the inference equalities as equality expressions that are partitioned by the symbolScope.
static boolean	isInferenceCandidate(Metadata metadata, Expression expression)	Determines whether an Expression may be successfully applied to the equality inference
static EqualityInference	newInstance(Metadata metadata, Expression... expressions)
static EqualityInference	newInstance(Metadata metadata, Collection<Expression> expressions)
static Stream<Expression>	nonInferrableConjuncts(Metadata metadata, Expression expression)	Provides a convenience Stream of Expression conjuncts which have not been added to the inference
Expression	rewrite(Expression expression, Set<Symbol> scope)	Attempts to rewrite an Expression in terms of the symbols allowed by the symbol scope given the known equalities.

Methods inherited from class java.lang.Object

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

Method Details

rewrite

public Expression rewrite(Expression expression,
 Set<Symbol> scope)

Attempts to rewrite an Expression in terms of the symbols allowed by the symbol scope given the known equalities. Returns null if unsuccessful.

generateEqualitiesPartitionedBy

public EqualityInference.EqualityPartition generateEqualitiesPartitionedBy(Set<Symbol> scope)

Dumps the inference equalities as equality expressions that are partitioned by the symbolScope. All stored equalities are returned in a compact set and will be classified into three groups as determined by the symbol scope:

1. equalities that fit entirely within the symbol scope
2. equalities that fit entirely outside of the symbol scope
3. equalities that straddle the symbol scope

 Example:
   Stored Equalities:
     a = b = c
     d = e = f = g

   Symbol Scope:
     a, b, d, e

   Output EqualityPartition:
     Scope Equalities:
       a = b
       d = e
     Complement Scope Equalities
       f = g
     Scope Straddling Equalities
       a = c
       d = f
 

isInferenceCandidate

public static boolean isInferenceCandidate(Metadata metadata,
 Expression expression)

Determines whether an Expression may be successfully applied to the equality inference

newInstance

public static EqualityInference newInstance(Metadata metadata,
 Expression... expressions)

newInstance

public static EqualityInference newInstance(Metadata metadata,
 Collection<Expression> expressions)

nonInferrableConjuncts

public static Stream<Expression> nonInferrableConjuncts(Metadata metadata,
 Expression expression)

Provides a convenience Stream of Expression conjuncts which have not been added to the inference