Class VersionValue
- java.lang.Object
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- com.apple.foundationdb.record.query.predicates.VersionValue
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- All Implemented Interfaces:
PlanHashable
,Correlated<Value>
,Value
@API(EXPERIMENTAL) public class VersionValue extends Object implements Value
A value representing a version stamp.
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Nested Class Summary
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Nested classes/interfaces inherited from interface com.apple.foundationdb.record.query.plan.temp.Correlated
Correlated.BoundEquivalence
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Nested classes/interfaces inherited from interface com.apple.foundationdb.record.PlanHashable
PlanHashable.PlanHashKind
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Constructor Summary
Constructors Constructor Description VersionValue()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(Object other)
<M extends Message>
Objecteval(FDBRecordStoreBase<M> store, EvaluationContext context, FDBRecord<M> record, M message)
Set<CorrelationIdentifier>
getCorrelatedTo()
Returns the set ofCorrelationIdentifier
s this entity is correlated to.int
hashCode()
int
planHash(PlanHashable.PlanHashKind hashKind)
Return a hash similar tohashCode
, but with the additional guarantee that is is stable across JVMs.Value
rebase(AliasMap translationMap)
Rebases this and all other objects this objects is composed of using a given translation map.boolean
semanticEquals(Object other, AliasMap equivalenceMap)
Determine equality with respect to an equivalence map betweenCorrelationIdentifier
s based on semantic equality: equality of the plan fragments implementing under the given correlation bindings.int
semanticHashCode()
Return a semantic hash code for this object.-
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface com.apple.foundationdb.record.PlanHashable
planHash
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Methods inherited from interface com.apple.foundationdb.record.query.predicates.Value
asPlaceholder, withComparison
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Method Detail
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getCorrelatedTo
@Nonnull public Set<CorrelationIdentifier> getCorrelatedTo()
Description copied from interface:Correlated
Returns the set ofCorrelationIdentifier
s this entity is correlated to. This means that without a process that binds these correlations to values, theRelationalExpression
(or others that implement this interface) cannot even in principle produce a meaningful result. As often times entities that implement this interface use composition and effectively describe trees or DAGs, this method should be the set union of theCorrelationIdentifier
s this object is correlated to as well as all children, constituent parts, etc.- Specified by:
getCorrelatedTo
in interfaceCorrelated<Value>
- Returns:
- the set of
CorrelationIdentifier
s this entity is correlated to
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rebase
@Nonnull public Value rebase(@Nonnull AliasMap translationMap)
Description copied from interface:Correlated
Rebases this and all other objects this objects is composed of using a given translation map.- Specified by:
rebase
in interfaceCorrelated<Value>
- Parameters:
translationMap
- a map defining a translation fromCorrelationIdentifier
sids
toCorrelationIdentifier
sids'
. After the rebase, every correlation to anid
containedids
that is contained or referred to directly or indirectly bythis
must have been transformed to use the mapped counterpart ofid
id'
inids'
. IDs not contained in the translation map must remain unmodified by the rebase operation.- Returns:
- a new entity that has been rebased
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eval
@Nullable public <M extends Message> Object eval(@Nonnull FDBRecordStoreBase<M> store, @Nonnull EvaluationContext context, @Nullable FDBRecord<M> record, @Nullable M message)
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semanticEquals
public boolean semanticEquals(@Nullable Object other, @Nonnull AliasMap equivalenceMap)
Description copied from interface:Correlated
Determine equality with respect to an equivalence map betweenCorrelationIdentifier
s based on semantic equality: equality of the plan fragments implementing under the given correlation bindings. The contract of this variant ofequals()
differs from its regular Java counterpart. A correlation is mostly just one part inside of composition of objects that expresses a more complicated (correlated) structure such as a filter. For instanceq1.x = 5
uses a correlation toq1
. That entity representing the filter is said to be correlated toq1
. Similarly,q1.x = 6
is a different filter and is not equal under any correlation mapping. In contrast, consider a predicate where everything except the correlation is the same, such asq2.x = 5
. Without a binding, these two filters are not the same. However, the filters may be a part of some other entity that can express correlations:SELECT * FROM T as q1 WHERE q1.x = 5
is equal toSELECT * FROM T as q2 WHERE q2.x = 5
. It does not matter thatq1
andq2
are named differently. It is important, however, that their semantic meaning is the same. In the example bothq1
andq2
refer to a record typeT
which presumably is the same record type. Therefore, these two query blocks are the same, even though they are labelled differently. In the context of this method, we can establish equality betweenq1.x = 5
andq2.x = 5
if we know thatq1
andq2
refer to the same underlying entity. The equivalence map passed in encodes that equality betweenCorrelationIdentifier
s. Note: This method has the same interaction withObject.hashCode()
as the regularequals()
method. As we can only ever establish true equality using equivalence maps,hashCode()
implementations in implementors of this interface must not be dependent on any correlation identifiers used in the structure of the entity. Doing so might violate the fundamental property of hash codes:e1.equals(e2, ...) => e1.hashCode() == e2.hashCode()
- Specified by:
semanticEquals
in interfaceCorrelated<Value>
- Parameters:
other
- the other object to establish equality withequivalenceMap
- a map ofCorrelationIdentifier
sids
toids'
. A correlation identifierid
used inthis
should be considered equal to another correlation identifierid'
used inother
if either they are the same byObject.equals(java.lang.Object)
of if there is a mapping fromid
toid'
.- Returns:
true
if both entities are considered equal using the equivalences passed in,false
otherwise
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planHash
public int planHash(@Nonnull PlanHashable.PlanHashKind hashKind)
Description copied from interface:PlanHashable
Return a hash similar tohashCode
, but with the additional guarantee that is is stable across JVMs.- Specified by:
planHash
in interfacePlanHashable
- Parameters:
hashKind
- the "kind" of hash to calculate. Each kind of hash has a particular logic with regards to included and excluded items.- Returns:
- a stable hash code
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semanticHashCode
public int semanticHashCode()
Description copied from interface:Correlated
Return a semantic hash code for this object. The hash code must obey the convention that for any two objectso1
ando2
and for everyAliasMap
aliasMap
:o1.semanticEquals(o1, aliasMap)
followso1.semanticHash() == o2.semanticHash()
Correlated.semanticEquals(java.lang.Object, com.apple.foundationdb.record.query.plan.temp.AliasMap)
returnstrue
for these two objects the plan fragments are considered to produce the same result under the given correlations bindings. The left sideo1.semanticEquals(o1, aliasMap)
depends on anAliasMap
whileo1.semanticHash() == o2.semanticHash()
does not. Hence, the hash that is computed is identical regardless of possible bindings.- Specified by:
semanticHashCode
in interfaceCorrelated<Value>
- Returns:
- the semantic hash code
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