io.druid.segment

Interface DimensionSelector

All Superinterfaces:

ColumnValueSelector

All Known Implementing Classes:

BaseSingleValueDimensionSelector, FloatWrappingDimensionSelector, LongWrappingDimensionSelector, NullDimensionSelector, SingleScanTimeDimSelector

public interface DimensionSelector
extends ColumnValueSelector

Field Summary

Fields

Modifier and Type	Field and Description
static int	CARDINALITY_UNKNOWN

Method Summary

Modifier and Type	Method and Description
IndexedInts	getRow() Gets all values for the row inside of an IntBuffer.
int	getValueCardinality() Value cardinality is the cardinality of the different occurring values.
IdLookup	idLookup() Returns IdLookup if available for this DimensionSelector, or null.
String	lookupName(int id) The Name is the String name of the actual field.
ValueMatcher	makeValueMatcher(com.google.common.base.Predicate<String> predicate)
ValueMatcher	makeValueMatcher(String value)
boolean	nameLookupPossibleInAdvance() Returns true if it is possible to lookupName(int) by ids from 0 to getValueCardinality() before the rows with those ids are returned.

Field Detail

CARDINALITY_UNKNOWN

static final int CARDINALITY_UNKNOWN

See Also:

Constant Field Values

Method Detail

getRow

IndexedInts getRow()

Gets all values for the row inside of an IntBuffer. I.e. one possible implementation could be return IntBuffer.wrap(lookupExpansion(get());

Returns:

all values for the row as an IntBuffer

makeValueMatcher

ValueMatcher makeValueMatcher(String value)

Parameters:

value - nullable dimension value

makeValueMatcher

ValueMatcher makeValueMatcher(com.google.common.base.Predicate<String> predicate)

getValueCardinality

int getValueCardinality()

Value cardinality is the cardinality of the different occurring values. If there were 4 rows: A,B A B A Value cardinality would be 2. Cardinality may be unknown (e.g. the selector used by IncrementalIndex while reading input rows), in which case this method will return -1. If cardinality is unknown, you should assume this dimension selector has no dictionary, and avoid storing ids, calling "lookupId", or calling "lookupName" outside of the context of operating on a single row.

Returns:

the value cardinality, or -1 if unknown.

lookupName

String lookupName(int id)

The Name is the String name of the actual field. It is assumed that storage layers convert names into id values which can then be used to get the string value. For example A,B A A,B B getRow() would return getRow(0) => [0 1] getRow(1) => [0] getRow(2) => [0 1] getRow(3) => [1] and then lookupName would return: lookupName(0) => A lookupName(1) => B

Parameters:

id - id to lookup the field name for

Returns:

the field name for the given id

nameLookupPossibleInAdvance

boolean nameLookupPossibleInAdvance()

Returns true if it is possible to lookupName(int) by ids from 0 to getValueCardinality() before the rows with those ids are returned.

Returns false if lookupName(int) could be called with ids, returned from the most recent call of getRow() on this DimensionSelector, but not earlier. If getValueCardinality() of this DimensionSelector additionally returns CARDINALITY_UNKNOWN, lookupName() couldn't be called with ids, returned by not the most recent call of getRow(), i. e. names for ids couldn't be looked up "later". If getValueCardinality() returns a non-negative number, lookupName() could be called with any ids, returned from #getRow() since the creation of this DimensionSelector.

If lookupName(int) is called with an ineligible id, result is undefined: exception could be thrown, or null returned, or some other random value.

idLookup

@Nullable
IdLookup idLookup()

Returns IdLookup if available for this DimensionSelector, or null.