io.prestosql.plugin.hive

Class ReaderProjections

java.lang.Object

io.prestosql.plugin.hive.ReaderProjections

public class ReaderProjections
extends Object

Stores a mapping of the projected columns required by HivePageSource to the columns supplied by format-specific page sources or record cursors.

Method Summary

Modifier and Type	Method and Description
List<HiveColumnHandle>	getReaderColumns() returns the actual list of columns being read by underlying page source or record cursor in order.
static Optional<ReaderProjections>	projectBaseColumns(List<HiveColumnHandle> columns) Creates a mapping between the input and base columns if required.
static Optional<ReaderProjections>	projectSufficientColumns(List<HiveColumnHandle> columns) Creates a set of sufficient columns for the input projected columns and prepares a mapping between the two.
HiveColumnHandle	readerColumnForHiveColumnAt(int index) For a column required by the HivePageSource, returns the column read by the delegate page source or record cursor.
int	readerColumnPositionForHiveColumnAt(int index) For a channel expected by HivePageSource, returns the channel index in the underlying page source or record cursor.

Methods inherited from class java.lang.Object

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

Method Detail

readerColumnForHiveColumnAt

public HiveColumnHandle readerColumnForHiveColumnAt(int index)

For a column required by the HivePageSource, returns the column read by the delegate page source or record cursor.

readerColumnPositionForHiveColumnAt

public int readerColumnPositionForHiveColumnAt(int index)

For a channel expected by HivePageSource, returns the channel index in the underlying page source or record cursor.

getReaderColumns

public List<HiveColumnHandle> getReaderColumns()

returns the actual list of columns being read by underlying page source or record cursor in order.

projectBaseColumns

public static Optional<ReaderProjections> projectBaseColumns(List<HiveColumnHandle> columns)

Creates a mapping between the input and base columns if required.

projectSufficientColumns

public static Optional<ReaderProjections> projectSufficientColumns(List<HiveColumnHandle> columns)

Creates a set of sufficient columns for the input projected columns and prepares a mapping between the two. For example, if input include columns "a.b" and "a.b.c", then they will be projected from a single column "a.b".