Package io.deephaven.engine.rowset.impl.rsp.container

Class RankCursor

java.lang.Object

io.deephaven.engine.rowset.impl.rsp.container.RankCursor

public final class RankCursor
extends Object

Rank navigation within a single container that resumes from where the previous query left off.

Container.select(int), Container.find(short) and Container.getShortRangeIterator(int) on a BitmapContainer count words from the start of the bitmap on every call, and on a RunContainer count runs from the first run, so a loop asking about consecutive ranks or values in one container does work proportional to the square of the number of queries. This cursor remembers the word or run it last stopped at, together with the number of values before it. A query at or beyond that point continues from there; one behind it starts over. Ascending queries, the common case for bulk operations, cost the container's length once in total.

For the other container kinds these queries are already cheap, and the cursor delegates to the container.

The cursor's position describes the container as it was when reset(io.deephaven.engine.rowset.impl.rsp.container.Container) was called. A container mutated since must be reset(io.deephaven.engine.rowset.impl.rsp.container.Container) again before the cursor is used. Cursors are not thread safe.

Constructor Summary

Constructors

Constructor	Description
RankCursor()

Method Summary

Modifier and Type	Method	Description
static boolean	benefits(Container c)
Container	container()
int	find(short x)	As Container.find(short).
SearchRangeIterator	getShortRangeIterator(int rank)	As Container.getShortRangeIterator(int).
void	reset(Container c)	Point the cursor at the start of c.
short	select(int rank)	As Container.select(int).

Methods inherited from class java.lang.Object

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

Constructor Details

RankCursor

public RankCursor()

Method Details

benefits

public static boolean benefits(Container c)

Returns:

whether queries on c through a cursor save work over the container's own methods

reset

public void reset(Container c)

Point the cursor at the start of c.

container

public Container container()

Returns:

the container the cursor was last reset(io.deephaven.engine.rowset.impl.rsp.container.Container) to, or null

select

public short select(int rank)

As Container.select(int).

find

public int find(short x)

As Container.find(short).

getShortRangeIterator

public SearchRangeIterator getShortRangeIterator(int rank)

As Container.getShortRangeIterator(int). Prefer Container.getShortRangeIterator(int, RankCursor) from a call site that sees one container type: the iterator is then created at a single site inside the container's own method, where the JIT can inline and scalar-replace it, rather than at one of several sites here.