io.prestosql.sql.planner

Class EqualityInference

java.lang.Object

io.prestosql.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 and Description
static class	EqualityInference.Builder
static class	EqualityInference.EqualityPartition

Method Summary

Modifier and Type	Method and Description
static EqualityInference	createEqualityInference(Expression... expressions)
EqualityInference.EqualityPartition	generateEqualitiesPartitionedBy(com.google.common.base.Predicate<Symbol> symbolScope) Dumps the inference equalities as equality expressions that are partitioned by the symbolScope.
static com.google.common.base.Predicate<Expression>	isInferenceCandidate() Determines whether an Expression may be successfully applied to the equality inference
static Iterable<Expression>	nonInferrableConjuncts(Expression expression) Provides a convenience Iterable of Expression conjuncts which have not been added to the inference
Expression	rewriteExpression(Expression expression, com.google.common.base.Predicate<Symbol> symbolScope) Attempts to rewrite an Expression in terms of the symbols allowed by the symbol scope given the known equalities.
Expression	rewriteExpressionAllowNonDeterministic(Expression expression, com.google.common.base.Predicate<Symbol> symbolScope) 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 Detail

rewriteExpression

public Expression rewriteExpression(Expression expression,
                                    com.google.common.base.Predicate<Symbol> symbolScope)

Attempts to rewrite an Expression in terms of the symbols allowed by the symbol scope given the known equalities. Returns null if unsuccessful. This method checks if rewritten expression is non-deterministic.

rewriteExpressionAllowNonDeterministic

public Expression rewriteExpressionAllowNonDeterministic(Expression expression,
                                                         com.google.common.base.Predicate<Symbol> symbolScope)

Attempts to rewrite an Expression in terms of the symbols allowed by the symbol scope given the known equalities. Returns null if unsuccessful. This method allows rewriting non-deterministic expressions.

generateEqualitiesPartitionedBy

public EqualityInference.EqualityPartition generateEqualitiesPartitionedBy(com.google.common.base.Predicate<Symbol> symbolScope)

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 com.google.common.base.Predicate<Expression> isInferenceCandidate()

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

nonInferrableConjuncts

public static Iterable<Expression> nonInferrableConjuncts(Expression expression)

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

createEqualityInference

public static EqualityInference createEqualityInference(Expression... expressions)