Package org.apache.druid.frame.write

Class FrameWriterUtils

java.lang.Object

org.apache.druid.frame.write.FrameWriterUtils

public class FrameWriterUtils
extends Object

Utility methods used by FrameWriter implementations.

Field Summary

Fields

Modifier and Type	Field	Description
static byte	NULL_STRING_MARKER
static byte[]	NULL_STRING_MARKER_ARRAY
static String	RESERVED_FIELD_PREFIX

Constructor Summary

Constructors

Constructor	Description
FrameWriterUtils()

Method Summary

Modifier and Type	Method	Description
static void	copyByteBufferToMemory(ByteBuffer src, org.apache.datasketches.memory.WritableMemory dst, long dstPosition, int len, boolean allowNullBytes)	Copies "len" bytes from src.position() to "dstPosition" in "memory".
static Set<String>	findDisallowedFieldNames(RowSignature signature)	Checks the provided signature for any disallowed field names.
static List<? extends Number>	getNumericArrayFromObject(Object row)	Retrieves a numeric list from a Java object, given that the object is an instance of something that can be returned from BaseObjectColumnValueSelector.getObject() of valid numeric array selectors representations While BaseObjectColumnValueSelector specifies that only instances of Object[] can be returned from the numeric array selectors, this method also handles a few more cases which can be encountered if the selector is directly implemented on top of the group by stuff
static List<ByteBuffer>	getUtf8ByteBuffersFromStringArraySelector(BaseObjectColumnValueSelector selector)	Retrieves UTF-8 byte buffers from a ColumnValueSelector, which is expected to be the kind of selector you get for an ARRAY<STRING> column.
static List<ByteBuffer>	getUtf8ByteBuffersFromStringSelector(DimensionSelector selector, boolean multiValue)	Retrieves UTF-8 byte buffers from a DimensionSelector, which is expected to be the kind of selector you get for an STRING column.
static RowSignature	replaceUnknownTypesWithNestedColumns(RowSignature rowSignature)
static void	verifySortColumns(List<KeyColumn> keyColumns, RowSignature signature)	Verifies whether the provided sortColumns are all sortable, and are a prefix of the signature.
static long	writeFrameHeader(org.apache.datasketches.memory.WritableMemory memory, long startPosition, FrameType frameType, long totalSize, int numRows, int numRegions, boolean permuted)	Writes a frame header to a memory locations.

Methods inherited from class java.lang.Object

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

Field Detail

NULL_STRING_MARKER

public static final byte NULL_STRING_MARKER

See Also:

Constant Field Values

NULL_STRING_MARKER_ARRAY

public static final byte[] NULL_STRING_MARKER_ARRAY

RESERVED_FIELD_PREFIX

public static final String RESERVED_FIELD_PREFIX

See Also:

Constant Field Values

Constructor Detail

FrameWriterUtils

public FrameWriterUtils()

Method Detail

writeFrameHeader

public static long writeFrameHeader(org.apache.datasketches.memory.WritableMemory memory,
                                    long startPosition,
                                    FrameType frameType,
                                    long totalSize,
                                    int numRows,
                                    int numRegions,
                                    boolean permuted)

Writes a frame header to a memory locations.

getUtf8ByteBuffersFromStringSelector

public static List<ByteBuffer> getUtf8ByteBuffersFromStringSelector(DimensionSelector selector,
                                                                    boolean multiValue)

Retrieves UTF-8 byte buffers from a DimensionSelector, which is expected to be the kind of selector you get for an STRING column. Null strings are returned as NULL_STRING_MARKER_ARRAY.

Parameters:

selector - the selector

multiValue - if true, return an array that corresponds exactly to DimensionSelector.getRow(). if false, always return a single-valued array. In particular, this means [] is returned as [NULL_STRING_MARKER_ARRAY].

Returns:

UTF-8 strings. The list itself is never null.

getUtf8ByteBuffersFromStringArraySelector

@Nullable
public static List<ByteBuffer> getUtf8ByteBuffersFromStringArraySelector(BaseObjectColumnValueSelector selector)

Retrieves UTF-8 byte buffers from a ColumnValueSelector, which is expected to be the kind of selector you get for an ARRAY<STRING> column. Null strings are returned as null. If the entire array returned by BaseObjectColumnValueSelector.getObject() is null, returns either null or NULL_STRING_MARKER_ARRAY depending on the value of "useNullArrays".

Parameters:

selector - array selector

Returns:

UTF-8 strings. The list itself may be null.

getNumericArrayFromObject

@Nullable
public static List<? extends Number> getNumericArrayFromObject(Object row)

Retrieves a numeric list from a Java object, given that the object is an instance of something that can be returned from BaseObjectColumnValueSelector.getObject() of valid numeric array selectors representations While BaseObjectColumnValueSelector specifies that only instances of Object[] can be returned from the numeric array selectors, this method also handles a few more cases which can be encountered if the selector is directly implemented on top of the group by stuff

findDisallowedFieldNames

public static Set<String> findDisallowedFieldNames(RowSignature signature)

Checks the provided signature for any disallowed field names. Returns any that are found.

verifySortColumns

public static void verifySortColumns(List<KeyColumn> keyColumns,
                                     RowSignature signature)

Verifies whether the provided sortColumns are all sortable, and are a prefix of the signature. This is required because it allows us to treat the sort key as a chunk of bytes. Exits quietly if the sort columns are OK. Throws an exception if there is a problem.

Throws:

IllegalArgumentException - if there is a problem

copyByteBufferToMemory

public static void copyByteBufferToMemory(ByteBuffer src,
                                          org.apache.datasketches.memory.WritableMemory dst,
                                          long dstPosition,
                                          int len,
                                          boolean allowNullBytes)

Copies "len" bytes from src.position() to "dstPosition" in "memory". Does not update the position of src.

Throws:

InvalidNullByteException - if "allowNullBytes" is false and a null byte is encountered

replaceUnknownTypesWithNestedColumns

public static RowSignature replaceUnknownTypesWithNestedColumns(RowSignature rowSignature)