datomic

Interface Database

public interface Database

An immutable, point-in-time database value.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	Database.Predicate<T> Boolean-valued function for filtering a database.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.Object	AEVT Names the AEVT index.
static java.lang.Object	AVET Names the AVET index.
static java.lang.Object	EAVT Names the EAVT index.
static java.lang.Object	VAET Names the VAET index.

Method Summary

Modifier and Type	Method and Description
Database	asOf(java.lang.Object t) Returns the value of the database filtered to include data up to t, inclusive
java.lang.Long	asOfT() asOf(Object) t value.
Attribute	attribute(java.lang.Object attrId) Returns information about an attribute.
long	basisT() t value of the most recent transaction in this db.
java.lang.Iterable<Datom>	datoms(java.lang.Object index, java.lang.Object... components) Implements the Datoms API for raw access to matching index data.
java.util.Map	dbStats() Queries for database stats.
java.lang.Object	entid(java.lang.Object entityId) Returns the entity id associated with any kind of entity identifier.
java.lang.Object	entidAt(java.lang.Object partition, java.lang.Object timePoint) Returns a fabricated entity id in the supplied partition whose T component is at or after the supplied t
Entity	entity(java.lang.Object entityId) Returns an entity: a lazy, dynamic associative view of datoms sharing an entity id.
Database	filter(Database.Predicate<Datom> pred) Returns a value of the database containing only Datoms satisfying the predicate.
Database	filter(java.lang.Object pred)
Database	history() Returns a history database value containing all assertions and retractions across time.
java.lang.String	id() Opaque, globally unique database id.
java.lang.Object	ident(java.lang.Object idOrKey) Returns the symbolic keyword associated with an id, or the key itself if passed.
java.util.stream.Stream<java.lang.Object>	indexPull(java.lang.Object options) "Walks an index, pulling entities via :e if :avet or :v if :aevt, using the selector, returning a Stream of the results.
java.lang.Iterable<Datom>	indexRange(java.lang.Object attrid, java.lang.Object start, java.lang.Object end) Returns a range of AVET-indexed datoms.
java.lang.Object	invoke(java.lang.Object entityId, java.lang.Object... args) Look up the database function of the entity at entityId, and invoke the function with args.
boolean	isFiltered() Does database have a filter set with e.g.
boolean	isHistory() True for databases created with history()
long	nextT() next t value that will be assigned by this database.
java.util.Map	pull(java.lang.Object pattern, java.lang.Object entityId) Returns a hierarchical selection of attributes for entityId.
java.util.List<java.util.Map>	pullMany(java.lang.Object pattern, java.util.List entityIds) Returns hierarchical selections of attributes for entityIds.
java.lang.Iterable<Datom>	seekDatoms(java.lang.Object index, java.lang.Object... components) Raw access to index data, starting at nearest match to input
Database	since(java.lang.Object t) Returns the value of the database filtered to include only data since t, exclusive
java.lang.Long	sinceT() since(Object) t value.
java.util.Map	with(java.util.List txData) Returns a database with txData applied locally in memory.

Field Detail

EAVT

static final java.lang.Object EAVT

Names the EAVT index.

Pass to APIs that take an index name such as datoms(Object, Object...).

AEVT

static final java.lang.Object AEVT

Names the AEVT index.

Pass to APIs that take an index name such as datoms(Object, Object...).

AVET

static final java.lang.Object AVET

Names the AVET index.

Pass to APIs that take an index name such as datoms(Object, Object...).

VAET

static final java.lang.Object VAET

Names the VAET index.

Pass to APIs that take an index name such as datoms(Object, Object...).

Method Detail

id

java.lang.String id()

Opaque, globally unique database id.

Returns:

the database id

basisT

long basisT()

t value of the most recent transaction in this db.

Returns:

a t value

nextT

long nextT()

next t value that will be assigned by this database.

Returns:

a t value

asOfT

java.lang.Long asOfT()

asOf(Object) t value.

Returns:

a t value, or null

sinceT

java.lang.Long sinceT()

since(Object) t value.

Returns:

a t value, or null

isHistory

boolean isHistory()

True for databases created with history()

Returns:

true for history databases

with

java.util.Map with(java.util.List txData)

Returns a database with txData applied locally in memory.

It is as if the data was applied in a transaction, but no actual transaction takes place.

Parameters:

txData - in the same format as expected by transact

Returns:

a map as returned by transact

asOf

Database asOf(java.lang.Object t)

Returns the value of the database filtered to include data up to t, inclusive

Parameters:

t - a time-point

Returns:

the value of the database as of some point t, inclusive

since

Database since(java.lang.Object t)

Returns the value of the database filtered to include only data since t, exclusive

Parameters:

t - a time-point

Returns:

the value of the database since some point t, exclusive

history

Database history()

Returns a history database value containing all assertions and retractions across time.

A history database can be used for datoms(Object, Object...) and indexRange(Object, Object, Object), for queries, and for asOf(Object) and since(Object).

A history database cannot be used with APIs that require a single point-in-time, i.e. entity(Object) or with(java.util.List).

Note that queries will return all of the additions and retractions, which can be distinguished by Datom.added()

Returns:

a history Database

filter

Database filter(Database.Predicate<Datom> pred)

Returns a value of the database containing only Datoms satisfying the predicate.

The predicate will be passed the unfiltered db and a Datom Chained calls to filter compose predicates with logical 'and'.

Parameters:

pred - a Predicate<Datom> or clojure fn

Returns:

the value of the database satisfying the predicate

Since:

0.8.3627

filter

Database filter(java.lang.Object pred)

isFiltered

boolean isFiltered()

Does database have a filter set with e.g. filter(datomic.Database.Predicate)?

Returns:

true if db has a filter

Since:

0.8.3627

entity

Entity entity(java.lang.Object entityId)

Returns an entity: a lazy, dynamic associative view of datoms sharing an entity id.

Parameters:

entityId - an entity identifier

Returns:

an Entity

attribute

Attribute attribute(java.lang.Object attrId)

Returns information about an attribute.

Parameters:

attrId - an entity identifier for an attribute

Returns:

an Attribute}

Since:

0.9.4470

ident

java.lang.Object ident(java.lang.Object idOrKey)

Returns the symbolic keyword associated with an id, or the key itself if passed.

Parameters:

idOrKey - an id or keyword

Returns:

a keyword, or nil if not found

entid

java.lang.Object entid(java.lang.Object entityId)

Returns the entity id associated with any kind of entity identifier.

Parameters:

entityId - an entity identifier

Returns:

an id, or nil if not found

entidAt

java.lang.Object entidAt(java.lang.Object partition,
                         java.lang.Object timePoint)

Returns a fabricated entity id in the supplied partition whose T component is at or after the supplied t

. Entity ids sort by partition, then T component, such T components interleaving with transaction numbers. Thus this method can be used to fabricate a time-based entity id component for use in #seekDatoms.

Parameters:

partition - an entity identifier for a partition

timePoint - a time-point

Returns:

a fabricated entity id at or after some point t

invoke

java.lang.Object invoke(java.lang.Object entityId,
                        java.lang.Object... args)

Look up the database function of the entity at entityId, and invoke the function with args.

Parameters:

entityId - an entity identifier

args - the arguments to the database function

Returns:

the return value of the database function

datoms

java.lang.Iterable<Datom> datoms(java.lang.Object index,
                                 java.lang.Object... components)

Implements the Datoms API for raw access to matching index data.

The index must be supplied, and, optionally, one or more leading components of the index can be supplied to narrow the result. EAVT and AEVT indexes will contain all datoms AVET will contain datoms for attributes where either :db/index or :db/unique are true. VAET will contain datoms for attributes of :db.type/ref - it is the reverse index

Parameters:

index - one of EAVT, AEVT, AVET, or VAET

components - supply any datom components to match, in order corresponding to the index

Returns:

the datoms in the specified index matching the specified components

seekDatoms

java.lang.Iterable<Datom> seekDatoms(java.lang.Object index,
                                     java.lang.Object... components)

Raw access to index data, starting at nearest match to input

. Arguments are the same as to datoms(java.lang.Object, java.lang.Object...), but their interpretation is different in two important ways:

1. The match need not be exact. Results will begin with the closest matching datom
2. No termination. Results will continue all the way to the end of the index.

seekDatoms is for more advanced applications, and datoms(Object, Object...) should be preferred wherever it is adequate. seekDatoms is typically used in conjunction with entidAt(Object, Object) to implement new entity scans.

Parameters:

index - one of EAVT, AEVT, AVET, or VAET

components - supply any datom components to search for, in order corresponding to the index

Returns:

all of the datoms in the specified index at or after the specified components

indexRange

java.lang.Iterable<Datom> indexRange(java.lang.Object attrid,
                                     java.lang.Object start,
                                     java.lang.Object end)

Returns a range of AVET-indexed datoms.

Parameters:

attrid - an entity identifier naming an indexed attribute.

start - start value or null if from beginning

end - end value (non-inclusive), or null if through end

Returns:

an Iterable over Datom positioned between start (inclusive) and end (exclusive)

pull

java.util.Map pull(java.lang.Object pattern,
                   java.lang.Object entityId)

Returns a hierarchical selection of attributes for entityId.

Parameters:

pattern - A pattern, or a String containing a pattern serialized into edn.

entityId - An entity identifier

Returns:

A map containing a selection for the entityId passed in.

Since:

0.9.5040

indexPull

java.util.stream.Stream<java.lang.Object> indexPull(java.lang.Object options)

"Walks an index, pulling entities via :e if :avet or :v if :aevt, using the selector, returning a Stream of the results.

Parameters:

options - a data structure describing the indexPull serialized into edn

• a map that includes the :index, :selector, :start, and :reverse keys

:index	:avet or :aevt
:selector	a pull selector (see 'pull')
:start	A vector in the same order as the index indicating the initial position. At least :a must be specified. Iteration is limited to datoms matching :a.
:reverse	optional, when true iterate the index in reverse order

Returns:

an Stream of the indexPull results

Since:

0.9.6079

pullMany

java.util.List<java.util.Map> pullMany(java.lang.Object pattern,
                                       java.util.List entityIds)

Returns hierarchical selections of attributes for entityIds.

Parameters:

pattern - A pattern, or a String containing a pattern serialized into edn.

entityIds - A list of entity identifiers

Returns:

A list of maps containing a selection for each entityId passed in.

Since:

0.9.5040

dbStats

java.util.Map dbStats()

Queries for database stats.

Returns:

a map with at least the following keys:

:datoms

total count of datoms in the (history) database