io.delta.kernel

Interface Scan

All Known Implementing Classes:

ScanImpl

@Evolving
public interface Scan

Represents a scan of a Delta table.

Since:

3.0.0

Method Summary

Modifier and Type	Method and Description
java.util.Optional<Predicate>	getRemainingFilter() Get the remaining filter that is not guaranteed to be satisfied for the data Delta Kernel returns.
CloseableIterator<FilteredColumnarBatch>	getScanFiles(Engine engine) Get an iterator of data files to scan.
Row	getScanState(Engine engine) Get the scan state associated with the current scan.
static CloseableIterator<FilteredColumnarBatch>	transformPhysicalData(Engine engine, Row scanState, Row scanFile, CloseableIterator<ColumnarBatch> physicalDataIter) Transform the physical data read from the table data file into the logical data that expected out of the Delta table.

Method Detail

getScanFiles

CloseableIterator<FilteredColumnarBatch> getScanFiles(Engine engine)

Get an iterator of data files to scan.

Parameters:

engine - Engine instance to use in Delta Kernel.

Returns:

iterator of FilteredColumnarBatchs where each selected row in the batch corresponds to one scan file. Schema of each row is defined as follows:

1. • name: add, type: struct
   • Description: Represents `AddFile` DeltaLog action
   • • name: path, type: string, description: location of the file.
     • name: partitionValues, type: map(string, string), description: A map from partition column to value for this logical file.
     • name: size, type: log, description: size of the file.
     • name: modificationTime, type: log, description: the time this logical file was created, as milliseconds since the epoch.
     • name: dataChange, type: boolean, description: When false the logical file must already be present in the table or the records in the added file must be contained in one or more remove actions in the same version
     • name: deletionVector, type: string, description: Either null (or absent in JSON) when no DV is associated with this data file, or a struct (described below) that contains necessary information about the DV that is part of this logical file. For description of each member variable in `deletionVector` @see Protocol
       • name: storageType, type: string
       • name: pathOrInlineDv, type: string
       • name: offset, type: log
       • name: sizeInBytes, type: log
       • name: cardinality, type: log
2. • name: tableRoot, type: string
   • Description: Absolute path of the table location. NOTE: this is temporary. Will be removed in future. @see

getRemainingFilter

java.util.Optional<Predicate> getRemainingFilter()

Get the remaining filter that is not guaranteed to be satisfied for the data Delta Kernel returns. This filter is used by Delta Kernel to do data skipping when possible.

Returns:

the remaining filter as a Predicate.

getScanState

Row getScanState(Engine engine)

Get the scan state associated with the current scan. This state is common across all files in the scan to be read.

Parameters:

engine - Engine instance to use in Delta Kernel.

Returns:

Scan state in Row format.

transformPhysicalData

static CloseableIterator<FilteredColumnarBatch> transformPhysicalData(Engine engine,
                                                                      Row scanState,
                                                                      Row scanFile,
                                                                      CloseableIterator<ColumnarBatch> physicalDataIter)
                                                               throws java.io.IOException

Transform the physical data read from the table data file into the logical data that expected out of the Delta table.

Parameters:

engine - Connector provided Engine implementation.

scanState - Scan state returned by getScanState(Engine)

scanFile - Scan file from where the physical data physicalDataIter is read from.

physicalDataIter - Iterator of ColumnarBatchs containing the physical data read from the scanFile.

Returns:

Data read from the input scan files as an iterator of FilteredColumnarBatchs. Each FilteredColumnarBatch instance contains the data read and an optional selection vector that indicates data rows as valid or invalid. It is the responsibility of the caller to close this iterator.

Throws:

java.io.IOException - when error occurs while reading the data.