Package io.delta.kernel.internal.replay

Class CreateCheckpointIterator

Object

io.delta.kernel.internal.replay.CreateCheckpointIterator

All Implemented Interfaces:

CloseableIterator<FilteredColumnarBatch>, Closeable, AutoCloseable, Iterator<FilteredColumnarBatch>

public class CreateCheckpointIterator
extends Object
implements CloseableIterator<FilteredColumnarBatch>

Replays a history of actions from the transaction log to reconstruct the checkpoint state of the table. The rules for constructing the checkpoint state are defined in the Delta Protocol: Checkpoint Reconciliation Rules.

Currently, the following rules are implemented:

• The latest protocol action seen wins
• The latest metaData action seen wins
• For txn actions, the latest version seen for a given appId wins
• Logical files in a table are identified by their (path, deletionVector.uniqueId) primary key. File actions (add or remove) reference logical files, and a log can contain any number of references to a single file.
• To replay the log, scan all file actions and keep only the newest reference for each logical file.
• add actions in the result identify logical files currently present in the table (for queries). remove actions in the result identify tombstones of logical files no longer present in the table (for VACUUM).
• commit info actions are not included

Following rules are not implemented. They will be implemented as we add support for more table features over time.

• For domainMetadata, the latest domainMetadata seen for a given domain wins.

Constructor Summary

Constructors

Constructor	Description
CreateCheckpointIterator(Engine engine, LogSegment logSegment, long minFileRetentionTimestampMillis)

Method Summary

Modifier and Type	Method	Description
void	close()
long	getNumberOfAddActions()	Number of add files in the final checkpoint.
boolean	hasNext()	Returns true if the iteration has more elements.
FilteredColumnarBatch	next()	Returns the next element in the iteration.

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.delta.kernel.utils.CloseableIterator

combine, filter, map

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Constructor Details

CreateCheckpointIterator

public CreateCheckpointIterator(Engine engine,
 LogSegment logSegment,
 long minFileRetentionTimestampMillis)

Method Details

hasNext

public boolean hasNext()

Description copied from interface: CloseableIterator

Returns true if the iteration has more elements. (In other words, returns true if next would return an element rather than throwing an exception.)

Specified by:

hasNext in interface CloseableIterator<FilteredColumnarBatch>

Specified by:

hasNext in interface Iterator<FilteredColumnarBatch>

Returns:

true if the iteration has more elements

next

public FilteredColumnarBatch next()

Description copied from interface: CloseableIterator

Returns the next element in the iteration.

Specified by:

next in interface CloseableIterator<FilteredColumnarBatch>

Specified by:

next in interface Iterator<FilteredColumnarBatch>

Returns:

the next element in the iteration

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

getNumberOfAddActions

public long getNumberOfAddActions()

Number of add files in the final checkpoint. Should be called once the entire data of this iterator is consumed.

Returns:

Number of add files in checkpoint.