Package io.delta.kernel.internal

Class ScanBuilderImpl

Object

io.delta.kernel.internal.ScanBuilderImpl

All Implemented Interfaces:

ScanBuilder

public class ScanBuilderImpl
extends Object
implements ScanBuilder

Implementation of ScanBuilder.

Constructor Summary

Constructors

Constructor	Description
ScanBuilderImpl(Path dataPath, Protocol protocol, Metadata metadata, StructType snapshotSchema, LogReplay logReplay, Engine engine)

Method Summary

Modifier and Type	Method	Description
Scan	build()
ScanBuilder	withFilter(Engine engine, Predicate predicate)	Apply the given filter expression to prune any files that do not possibly contain the data that satisfies the given filter.
ScanBuilder	withReadSchema(Engine engine, StructType readSchema)	Apply the given readSchema.

Methods inherited from class java.lang.Object

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

Constructor Details

ScanBuilderImpl

public ScanBuilderImpl(Path dataPath,
 Protocol protocol,
 Metadata metadata,
 StructType snapshotSchema,
 LogReplay logReplay,
 Engine engine)

Method Details

withFilter

public ScanBuilder withFilter(Engine engine,
 Predicate predicate)

Description copied from interface: ScanBuilder

Apply the given filter expression to prune any files that do not possibly contain the data that satisfies the given filter.

Kernel makes use of the scan file partition values (for partitioned tables) and file-level column statistics (min, max, null count etc.) in the Delta metadata for filtering. Sometimes these metadata is not enough to deterministically say a scan file doesn't contain data that satisfies the filter.

E.g. given filter is a = 2. In file A, column a has min value as -40 and max value as 200. In file B, column a has min value as 78 and max value as 323. File B can be ruled out as it cannot possibly have rows where `a = 2`, but file A cannot be ruled out as it may contain rows where a = 2.

As filtering is a best effort, the Scan object may return scan files (through Scan.getScanFiles(Engine)) that does not satisfy the filter. It is the responsibility of the caller to apply the remaining filter returned by Scan.getRemainingFilter() to the data read from the scan files (returned by Scan.getScanFiles(Engine)) to completely filter out the data that doesn't satisfy the filter.```

Specified by:

withFilter in interface ScanBuilder

Parameters:

engine - Engine instance to use in Delta Kernel.

predicate - a Predicate to prune the metadata or data.

Returns:

A ScanBuilder with filter applied.

withReadSchema

public ScanBuilder withReadSchema(Engine engine,
 StructType readSchema)

Description copied from interface: ScanBuilder

Apply the given readSchema. If the builder already has a projection applied, calling this again replaces the existing projection.

Specified by:

withReadSchema in interface ScanBuilder

Parameters:

engine - Engine instance to use in Delta Kernel.

readSchema - Subset of columns to read from the Delta table.

Returns:

A ScanBuilder with projection pruning.

build

public Scan build()

Specified by:

build in interface ScanBuilder

Returns:

Build the instance