kudu::client::KuduColumnarScanBatch Class Reference

A batch of columnar data returned from a scanner. More...

#include <columnar_scan_batch.h>

Public Member Functions
int	NumRows () const
Status	GetFixedLengthColumn (int idx, Slice *data) const
Status	GetVariableLengthColumn (int idx, Slice *offsets, Slice *data) const
Status	GetNonNullBitmapForColumn (int idx, Slice *data) const

Detailed Description

A batch of columnar data returned from a scanner.

Similar to KuduScanBatch, this contains a batch of rows returned from a scanner. This type of batch is used if the KuduScanner::COLUMNAR_LAYOUT row format flag is enabled.

Retrieving rows in columnar layout can be significantly more efficient. It saves some CPU cycles on the Kudu cluster and can also enable faster processing of the returned data in certain client applications.

The columnar data retrieved by this class matches the columnar encoding described by Apache Arrow[1], but without the alignment and padding guarantees that are made by the Arrow IPC serialization.

[1] https://arrow.apache.org/docs/format/Columnar.html

NOTE: this class is not thread-safe.

Member Function Documentation

GetFixedLengthColumn()

Status kudu::client::KuduColumnarScanBatch::GetFixedLengthColumn	(	int	idx,
		Slice *	data
	)		const

Get the raw columnar data corresponding to the primitive-typed column with index 'idx'.

For variable-length (e.g. STRING, BINARY, VARCHAR) columns, use GetVariableLengthColumn instead.

Note

The Slice returned is only valid for the lifetime of the KuduColumnarScanBatch.

Parameters

[in]	idx	The column index.
[out]	data	The data is in little-endian packed array format. No alignment or padding is guaranteed. Space is reserved for all cells regardless of whether they might be null. The data stored in a null cell may or may not be zeroed.

Returns

Operation result status.

GetNonNullBitmapForColumn()

Status kudu::client::KuduColumnarScanBatch::GetNonNullBitmapForColumn	(	int	idx,
		Slice *	data
	)		const

Get a bitmap corresponding to the non-null status of the cells in the given column.

It is an error to call this function on a column which is not marked as nullable in the schema.

Note

The Slice returned is only valid for the lifetime of the KuduColumnarScanBatch.

Parameters

[in]	idx	The column index.
[out]	data	The bitmap corresponding to the non-null status of the cells in the given column. A set bit indicates a non-null cell. If the number of rows is not a multiple of 8, the state of the trailing bits in the bitmap is undefined.

Returns

Operation result status.

GetVariableLengthColumn()

Status kudu::client::KuduColumnarScanBatch::GetVariableLengthColumn	(	int	idx,
		Slice *	offsets,
		Slice *	data
	)		const

Return the variable-length data for the variable-length-typed column with index 'idx'.

Parameters

[in]	idx	The column index.
[out]	offsets	If NumRows() is 0, the 'offsets' array will have length 0. Otherwise, this array will contain NumRows() + 1 entries, each indicating an offset within the variable-length data array returned in 'data'. For each cell with index 'n', offsets[n] indicates the starting offset of that cell, and offsets[n+1] indicates the ending offset of that cell.
[out]	data	The variable-length data.

Returns

Operation result status.

NumRows()

int kudu::client::KuduColumnarScanBatch::NumRows

(

)

const

Returns

The number of rows in this batch.

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The documentation for this class was generated from the following file:

• include/kudu/client/columnar_scan_batch.h