Module org.yamcs.core

Package org.yamcs.parameterarchive

Class SegmentIterator

java.lang.Object

org.yamcs.parameterarchive.SegmentIterator

All Implemented Interfaces:

AutoCloseable, ParchiveIterator<ParameterValueSegment>, PeekingIterator<ParameterValueSegment>

public class SegmentIterator
extends Object
implements ParchiveIterator<ParameterValueSegment>

For a given simple parameter id and group id, iterates over all segments in the parameter archive (across all partitions).

Provides objects of type ParameterValueSegment which contain multiple values of one parameter - suitable to be used for bulk processing (e.g. downsampling or averaging).

The ParameterIterator can be used to iterate over parameters value by value (at the expense of consuming more memory)

This iterator works like a Rocks iterator (with isValid(), next(), and value()) not like a java one. The advantage is that one can look at the current value multiple times. This property is used when merging the iterators using a priority queue.

The iterator has to be closed if it is not used until the end, otherwise a rocks iterator may be left hanging

Note about the raw values retrieval: the retrieval assumes that if raw values are requested, the parameter has raw values (this can be known from the type associated to the parameter id).

Thus, if the raw values are requested and not found in the archive, the engineering values are returned as raw values. This is an optimisation done in case the two are equal.

The iterator also sends data from RealtimeFiller if that is enabled.

Constructor Summary

Constructors

Constructor	Description
SegmentIterator(ParameterArchive parchive, ParameterId parameterId, int parameterGroupId, ParameterRequest req)

Method Summary

Modifier and Type	Method	Description
void	close()	Close the underlying rocks iterator if not already closed
int	getParameterGroupId()
ParameterId	getParameterId()
boolean	isValid()	Returns true if the iterator has more elements.
void	next()	Moves the iterator to the next element.
ParameterValueSegment	value()	Returns the current value from the iterator without advancing.

Methods inherited from class java.lang.Object

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

Constructor Details

SegmentIterator

public SegmentIterator(ParameterArchive parchive,
 ParameterId parameterId,
 int parameterGroupId,
 ParameterRequest req)

Method Details

isValid

public boolean isValid()

Description copied from interface: PeekingIterator

Returns true if the iterator has more elements.

This method allows to verify whether the iterator has a valid value to be fetched.

Specified by:

isValid in interface PeekingIterator<ParameterValueSegment>

Returns:

true if the iterator has more elements or false otherwise

value

public ParameterValueSegment value()

Description copied from interface: PeekingIterator

Returns the current value from the iterator without advancing.

This method can only be called if PeekingIterator.isValid() returns true. If called after PeekingIterator.isValid() returns false, this method will throw an exception.

Specified by:

value in interface PeekingIterator<ParameterValueSegment>

Returns:

the current element

next

public void next()

Description copied from interface: PeekingIterator

Moves the iterator to the next element.

If PeekingIterator.isValid() returns false, calling this method has no effect.

Specified by:

next in interface PeekingIterator<ParameterValueSegment>

close

public void close()

Close the underlying rocks iterator if not already closed

Specified by:

close in interface AutoCloseable

Specified by:

close in interface ParchiveIterator<ParameterValueSegment>

getParameterGroupId

public int getParameterGroupId()

getParameterId

public ParameterId getParameterId()