org.apache.druid.segment.column

Interface ColumnIndexSupplier

All Known Implementing Classes:

DictionaryEncodedStringIndexSupplier, NestedFieldLiteralColumnIndexSupplier, NoIndexesColumnIndexSupplier, NullValueIndexSupplier, StringFrontCodedColumnIndexSupplier

public interface ColumnIndexSupplier

Provides indexes and information about them (ColumnIndexCapabilities) for a column. Indexes which satisfy the Filter used in a Query, allow the query engine to construct Offset (and VectorOffset) to build Cursor (and VectorCursor). This allows the engine to only scan the rows which match the filter values, instead of performing a full scan of the column and using a ValueMatcher (or VectorValueMatcher) to filter the values.

Method Summary

Modifier and Type	Method and Description
<T> T	as(Class<T> clazz) Try to get a column 'index' of the specified type.

Method Detail

as

@Nullable
<T> T as(Class<T> clazz)

Try to get a column 'index' of the specified type. If the index of the desired type is not available, this method will return null. If the value is non-null, the index may be used for the eventual construction of an Offset to form the basis of a Cursor (or VectorOffset and VectorCursor) which can greatly reduce the total number of rows which need to be scanned and processed. Objects returned by this method are not thread-safe.