org.apache.druid.segment

Interface StorageAdapter

All Superinterfaces:

ColumnInspector, CursorFactory, Expr.InputBindingInspector

All Known Implementing Classes:

HashJoinSegmentStorageAdapter, IncrementalIndexStorageAdapter, QueryableIndexStorageAdapter, RowBasedStorageAdapter

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.
String	getColumnTypeName(String column) Like ColumnCapabilities.getType(), but may return a more descriptive string for complex columns.
int	getDimensionCardinality(String column) Returns the number of distinct values for the given column if known, or Integer.MAX_VALUE if unknown, e.
org.joda.time.Interval	getInterval()
org.joda.time.DateTime	getMaxIngestedEventTime()
org.joda.time.DateTime	getMaxTime()
Comparable	getMaxValue(String column)
Metadata	getMetadata()
org.joda.time.DateTime	getMinTime()
Comparable	getMinValue(String column)
int	getNumRows()
default boolean	hasBuiltInFilters() Returns true if this storage adapter can filter some rows out.

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

canVectorize, makeCursors, makeVectorCursor

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

getType

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

areNumeric, areNumeric, areScalar, areScalar, canVectorize, canVectorize

Method Detail

getInterval

org.joda.time.Interval getInterval()

getAvailableDimensions

Indexed<String> getAvailableDimensions()

getAvailableMetrics

Iterable<String> getAvailableMetrics()

getDimensionCardinality

int getDimensionCardinality(String column)

Returns the number of distinct values for the given column if known, or Integer.MAX_VALUE if unknown, e. g. the column is numeric. If the column doesn't exist, returns 0.

getMinTime

org.joda.time.DateTime getMinTime()

getMaxTime

org.joda.time.DateTime getMaxTime()

getMinValue

@Nullable
Comparable getMinValue(String column)

getMaxValue

@Nullable
Comparable getMaxValue(String column)

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

getColumnTypeName

@Nullable
String getColumnTypeName(String column)

Like ColumnCapabilities.getType(), but may return a more descriptive string for complex columns.

Parameters:

column - column name

Returns:

type name

getNumRows

int getNumRows()

getMaxIngestedEventTime

org.joda.time.DateTime getMaxIngestedEventTime()

getMetadata

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.