Package io.deephaven.engine.table.impl.select

Class DownsampledWhereFilter

java.lang.Object

io.deephaven.engine.table.impl.select.WhereFilterImpl

io.deephaven.engine.table.impl.select.DownsampledWhereFilter

All Implemented Interfaces:

ConcurrencyControl<Filter>, Expression, Filter, WhereFilter, Serializable

public class DownsampledWhereFilter
extends WhereFilterImpl

Utilities for downsampling non-ticking time series data within a query. The input table must be sorted by the Instant column to be used for binning rows.

Usage is of the form: downsampledX = x.where(new DownsampledWhereFilter("Timestamp", 5 * DateTimeUtils.MINUTE));

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	DownsampledWhereFilter.SampleOrder	Enum to use when selecting downsampling behavior:

Nested classes/interfaces inherited from interface io.deephaven.engine.table.impl.select.WhereFilter

WhereFilter.PreviousFilteringNotSupported, WhereFilter.RecomputeListener, WhereFilter.Visitor<T>

Field Summary

Fields inherited from interface io.deephaven.engine.table.impl.select.WhereFilter

ZERO_LENGTH_WHERE_FILTER_ARRAY

Constructor Summary

Constructors

Constructor	Description
DownsampledWhereFilter(String column, long binSize)	Creates a DownsampledWhereFilter which can be used in a .where clause to downsample time series rows.
DownsampledWhereFilter(String column, long binSize, DownsampledWhereFilter.SampleOrder order)	Creates a DownsampledWhereFilter which can be used in a .where clause to downsample time series rows.

Method Summary

Modifier and Type	Method	Description
DownsampledWhereFilter	copy()	Create a copy of this WhereFilter.
@NotNull WritableRowSet	filter(@NotNull RowSet selection, @NotNull RowSet fullSet, @NotNull Table table, boolean usePrev)	Filter selection to only matching rows.
List<String>	getColumnArrays()	Get the array columns required by this select filter.
List<String>	getColumns()	Get the columns required by this select filter.
void	init(@NotNull TableDefinition tableDefinition)	Initialize this filter given the table definition.
boolean	isSimpleFilter()
boolean	permitParallelization()	Returns true if this filter permits parallelism.
void	setRecomputeListener(WhereFilter.RecomputeListener listener)	Set the WhereFilter.RecomputeListener that should be notified if results based on this WhereFilter must be recomputed.

Methods inherited from class io.deephaven.engine.table.impl.select.WhereFilterImpl

isAutomatedFilter, setAutomatedFilter

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.deephaven.engine.table.impl.select.WhereFilter

beginOperation, canMemoize, filter, filterInverse, hasVirtualRowVariables, init, invert, isRefreshing, isSerial, validateSafeForRefresh, walk, walk, walk, withDeclaredBarriers, withRespectedBarriers, withSerial

Constructor Details

DownsampledWhereFilter

public DownsampledWhereFilter(String column,
 long binSize,
 DownsampledWhereFilter.SampleOrder order)

Creates a DownsampledWhereFilter which can be used in a .where clause to downsample time series rows.

Parameters:

column - Instant column to use for filtering.

binSize - Size in nanoseconds for the time bins. Constants like DateTimeUtils.MINUTE are typically used.

order - DownsampledWhereFilter.SampleOrder to set desired behavior.

DownsampledWhereFilter

public DownsampledWhereFilter(String column,
 long binSize)

Creates a DownsampledWhereFilter which can be used in a .where clause to downsample time series rows.

Parameters:

column - Instant column to use for filtering.

binSize - Size in nanoseconds for the time bins. Constants like DateTimeUtils.MINUTE are typically used.

Method Details

getColumns

public List<String> getColumns()

Description copied from interface: WhereFilter

Get the columns required by this select filter.

This filter must already be initialized before calling this method.

Returns:

the columns used as input by this select filter.

getColumnArrays

public List<String> getColumnArrays()

Description copied from interface: WhereFilter

Get the array columns required by this select filter.

This filter must already be initialized before calling this method.

Returns:

the columns used as array input by this select filter.

init

public void init(@NotNull
 @NotNull TableDefinition tableDefinition)

Description copied from interface: WhereFilter

Initialize this filter given the table definition. If this filter has already been initialized, this should be a no-op, or optionally validate that the table definition is compatible with previous initialization.

Parameters:

tableDefinition - the definition of the table that will be filtered

filter

@NotNull
public @NotNull WritableRowSet filter(@NotNull
 @NotNull RowSet selection,
 @NotNull
 @NotNull RowSet fullSet,
 @NotNull
 @NotNull Table table,
 boolean usePrev)

Description copied from interface: WhereFilter

Filter selection to only matching rows.

Parameters:

selection - the indices that should be filtered. The selection must be a subset of fullSet, and may include rows that the engine determines need not be evaluated to produce the result. Implementations may not mutate or close selection.

fullSet - the complete RowSet of the table to filter. The fullSet is used for calculating variables like "i" or "ii". Implementations may not mutate or close fullSet.

table - the table to filter

usePrev - true if previous values should be used. Implementing previous value filtering is optional, and a WhereFilter.PreviousFilteringNotSupported exception may be thrown. If a PreviousFiltering exception is thrown, then the caller must acquire the PeriodicUpdateGraph lock.

Returns:

The subset of selection accepted by this filter; ownership passes to the caller

isSimpleFilter

public boolean isSimpleFilter()

Returns:

true if this is a filter that does not require any code execution, but rather is handled entirely within the database engine.

setRecomputeListener

public void setRecomputeListener(WhereFilter.RecomputeListener listener)

Description copied from interface: WhereFilter

Set the WhereFilter.RecomputeListener that should be notified if results based on this WhereFilter must be recomputed.

Parameters:

listener - The WhereFilter.RecomputeListener to notify

copy

public DownsampledWhereFilter copy()

Description copied from interface: WhereFilter

Create a copy of this WhereFilter.

Returns:

an independent copy of this WhereFilter.

permitParallelization

public boolean permitParallelization()

Description copied from interface: WhereFilter

Returns true if this filter permits parallelism.

No serial filters permit parallelization. A filter may not permit parallelism if the internal implementation does not support multiple WhereFilter.filter(RowSet, RowSet, Table, boolean) calls (e.g., some special filters that operate only on a rowset or have external state). ConditionFilters automatically determine whether they permit parallelization based on whether filters are stateless by default.

Returns:

if this filter can be applied in parallel