org.apache.druid.segment

Interface StorageAdapter

All Superinterfaces:

ColumnInspector, CursorFactory, Expr.InputBindingInspector

All Known Implementing Classes:

FrameStorageAdapter, HashJoinSegmentStorageAdapter, IncrementalIndexStorageAdapter, QueryableIndexStorageAdapter, RowBasedStorageAdapter, UnnestStorageAdapter

public interface StorageAdapter
extends CursorFactory, ColumnInspector

Method Summary

Modifier and Type	Method and Description
Indexed<String>	getAvailableDimensions()
Iterable<String>	getAvailableMetrics()
ColumnCapabilities	getColumnCapabilities(String column) Returns capabilities of a particular column, if known.
int	getDimensionCardinality(String column) Returns the number of distinct values for a column, or DimensionDictionarySelector.CARDINALITY_UNKNOWN if unknown.
org.joda.time.Interval	getInterval()
org.joda.time.DateTime	getMaxIngestedEventTime()
org.joda.time.DateTime	getMaxTime() Metadata-only operation that returns an upper bound on ColumnHolder.TIME_COLUMN_NAME values for this adapter.
Comparable	getMaxValue(String column) Returns the minimum value of the provided column, if known through an index, dictionary, or cache.
Metadata	getMetadata()
org.joda.time.DateTime	getMinTime() Metadata-only operation that returns a lower bound on ColumnHolder.TIME_COLUMN_NAME values for this adapter.
Comparable	getMinValue(String column) Returns the minimum value of the provided column, if known through an index, dictionary, or cache.
int	getNumRows()
default RowSignature	getRowSignature() Returns the row signature of the data available from this adapter.
default boolean	hasBuiltInFilters() Returns true if this storage adapter can filter some rows out.
default boolean	isFromTombstone()

Methods inherited from interface org.apache.druid.segment.CursorFactory

canVectorize, makeCursors, makeVectorCursor

Methods inherited from interface org.apache.druid.segment.ColumnInspector

getColumnCapabilitiesWithDefault, getType

Methods inherited from interface org.apache.druid.math.expr.Expr.InputBindingInspector

areNumeric, areNumeric, areSameTypes, areSameTypes, areScalar, areScalar, canVectorize, canVectorize

Method Detail

getInterval

org.joda.time.Interval getInterval()

getAvailableDimensions

Indexed<String> getAvailableDimensions()

getAvailableMetrics

Iterable<String> getAvailableMetrics()

getRowSignature

default RowSignature getRowSignature()

Returns the row signature of the data available from this adapter. For mutable adapters, even though the signature may evolve over time, any particular object returned by this method is an immutable snapshot.

getDimensionCardinality

int getDimensionCardinality(String column)

Returns the number of distinct values for a column, or DimensionDictionarySelector.CARDINALITY_UNKNOWN if unknown. If the column doesn't exist, returns 1, because a column that doesn't exist is treated as a column of default (or null) values.

getMinTime

org.joda.time.DateTime getMinTime()

Metadata-only operation that returns a lower bound on ColumnHolder.TIME_COLUMN_NAME values for this adapter. May be earlier than the actual minimum data timestamp. For QueryableIndexStorageAdapter and IncrementalIndexStorageAdapter specifically, which back regular tables (i.e. TableDataSource), this method contract is tighter: it does return the actual minimum data timestamp. This fact is leveraged by TimeBoundaryQuery to return results using metadata only.

getMaxTime

org.joda.time.DateTime getMaxTime()

Metadata-only operation that returns an upper bound on ColumnHolder.TIME_COLUMN_NAME values for this adapter. May be later than the actual maximum data timestamp. For QueryableIndexStorageAdapter and IncrementalIndexStorageAdapter specifically, which back regular tables (i.e. TableDataSource), this method contract is tighter: it does return the actual maximum data timestamp. This fact is leveraged by TimeBoundaryQuery to return results using metadata only.

getMinValue

@Nullable
Comparable getMinValue(String column)

Returns the minimum value of the provided column, if known through an index, dictionary, or cache. Returns null if not known. Does not scan the column to find the minimum value.

getMaxValue

@Nullable
Comparable getMaxValue(String column)

Returns the minimum value of the provided column, if known through an index, dictionary, or cache. Returns null if not known. Does not scan the column to find the maximum value.

getColumnCapabilities

@Nullable
ColumnCapabilities getColumnCapabilities(String column)

Returns capabilities of a particular column, if known. May be null if the column doesn't exist, or if the column does exist but the capabilities are unknown. The latter is possible with dynamically discovered columns. Note that StorageAdapters are representations of "real" segments, so they are not aware of any virtual columns that may be involved in a query. In general, query engines should instead use the method ColumnSelectorFactory.getColumnCapabilities(String), which returns capabilities for virtual columns as well.

Specified by:

getColumnCapabilities in interface ColumnInspector

Parameters:

column - column name

Returns:

capabilities, or null

getNumRows

int getNumRows()

getMaxIngestedEventTime

org.joda.time.DateTime getMaxIngestedEventTime()

getMetadata

@Nullable
Metadata getMetadata()

hasBuiltInFilters

default boolean hasBuiltInFilters()

Returns true if this storage adapter can filter some rows out. The actual column cardinality can be lower than what getDimensionCardinality(java.lang.String) returns if this returns true. Dimension selectors for such storage adapter can return non-contiguous dictionary IDs because the dictionary IDs in filtered rows will not be returned. Note that the number of rows accessible via this storage adapter will not necessarily decrease because of the built-in filters. For inner joins, for example, the number of joined rows can be larger than the number of rows in the base adapter even though this method returns true.

isFromTombstone

default boolean isFromTombstone()

Returns:

true if this index was created from a tombstone or false otherwise