Package dev.morphia.aggregation.experimental.expressions

Class SystemVariables

java.lang.Object

dev.morphia.aggregation.experimental.expressions.SystemVariables

public final class SystemVariables
extends Object

Defines helper fields for referencing system variables

Field Summary

Fields

Modifier and Type	Field	Description
static Expression	CLUSTER_TIME	A variable that returns the current timestamp value.
static Expression	CURRENT	References the start of the field path being processed in the aggregation pipeline stage.
static Expression	DESCEND	One of the allowed results of a $redact expression.
static Expression	KEEP	One of the allowed results of a $redact expression.
static Expression	NOW	A variable that returns the current datetime value.
static Expression	PRUNE	One of the allowed results of a $redact expression.
static Expression	REMOVE	A variable which evaluates to the missing value.
static Expression	ROOT	References the root document, i.e.

Method Summary

Methods inherited from class java.lang.Object

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

Field Detail

CLUSTER_TIME

public static final Expression CLUSTER_TIME

A variable that returns the current timestamp value. CLUSTER_TIME is only available on replica sets and sharded clusters.

CLUSTER_TIME returns the same value for all members of the deployment and remains the same throughout all stages of the pipeline.

CURRENT

public static final Expression CURRENT

References the start of the field path being processed in the aggregation pipeline stage. Unless documented otherwise, all stages start with CURRENT the same as ROOT.

CURRENT is modifiable. However, since $ is equivalent to $$CURRENT., rebinding CURRENT changes the meaning of $ accesses.

DESCEND

public static final Expression DESCEND

One of the allowed results of a $redact expression.

KEEP

public static final Expression KEEP

One of the allowed results of a $redact expression.

NOW

public static final Expression NOW

A variable that returns the current datetime value. NOW returns the same value for all members of the deployment and remains the same throughout all stages of the aggregation pipeline.

PRUNE

public static final Expression PRUNE

One of the allowed results of a $redact expression.

REMOVE

public static final Expression REMOVE

A variable which evaluates to the missing value. Allows for the conditional exclusion of fields. In a $projection, a field set to the variable REMOVE is excluded from the output.

For an example of its usage, see Conditionally Exclude Fields.

ROOT

public static final Expression ROOT

References the root document, i.e. the top-level document, currently being processed in the aggregation pipeline stage.