io.delta.kernel.defaults.engine

Class DefaultJsonHandler

Object

io.delta.kernel.defaults.engine.DefaultJsonHandler

All Implemented Interfaces:

JsonHandler

public class DefaultJsonHandler
extends Object
implements JsonHandler

Default implementation of JsonHandler based on Hadoop APIs.

Constructor Summary

Constructors

Constructor and Description
DefaultJsonHandler(org.apache.hadoop.conf.Configuration hadoopConf)

Method Summary

Modifier and Type	Method and Description
StructType	deserializeStructType(String structTypeJson) Deserialize the Delta schema from structTypeJson according to the Delta Protocol schema serialization rules .
ColumnarBatch	parseJson(ColumnVector jsonStringVector, StructType outputSchema, java.util.Optional<ColumnVector> selectionVector) Parse the given json strings and return the fields requested by outputSchema as columns in a ColumnarBatch.
CloseableIterator<ColumnarBatch>	readJsonFiles(CloseableIterator<FileStatus> scanFileIter, StructType physicalSchema, java.util.Optional<Predicate> predicate) Read and parse the JSON format file at given locations and return the data as a ColumnarBatch with the columns requested by physicalSchema.
void	writeJsonFileAtomically(String filePath, CloseableIterator<Row> data, boolean overwrite) Makes use of LogStore implementations in `delta-storage` to atomically write the data to a file depending upon the destination filesystem.

Methods inherited from class Object

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

Constructor Detail

DefaultJsonHandler

public DefaultJsonHandler(org.apache.hadoop.conf.Configuration hadoopConf)

Method Detail

parseJson

public ColumnarBatch parseJson(ColumnVector jsonStringVector,
                               StructType outputSchema,
                               java.util.Optional<ColumnVector> selectionVector)

Description copied from interface: JsonHandler

Parse the given json strings and return the fields requested by outputSchema as columns in a ColumnarBatch.

There are a couple special cases that should be handled for specific data types:

• FloatType and DoubleType: handle non-numeric numbers encoded as strings
  • NaN: "NaN"
  • Positive infinity: "+INF", "Infinity", "+Infinity"
  • Negative infinity: "-INF", "-Infinity""
• DateType: handle dates encoded as strings in the format "yyyy-MM-dd"
• TimestampType: handle timestamps encoded as strings in the format "yyyy-MM-dd'T'HH:mm:ss.SSSXXX"

Specified by:

parseJson in interface JsonHandler

Parameters:

jsonStringVector - String ColumnVector of valid JSON strings.

outputSchema - Schema of the data to return from the parsed JSON. If any requested fields are missing in the JSON string, a null is returned for that particular field in the returned Row. The type for each given field is expected to match the type in the JSON.

selectionVector - Optional selection vector indicating which rows to parse the JSON. If present, only the selected rows should be parsed. Unselected rows should be all null in the returned batch.

Returns:

a ColumnarBatch of schema outputSchema with one row for each entry in jsonStringVector

deserializeStructType

public StructType deserializeStructType(String structTypeJson)

Description copied from interface: JsonHandler

Deserialize the Delta schema from structTypeJson according to the Delta Protocol schema serialization rules .

Specified by:

deserializeStructType in interface JsonHandler

Parameters:

structTypeJson - the JSON formatted schema string to parse

Returns:

the parsed StructType

readJsonFiles

public CloseableIterator<ColumnarBatch> readJsonFiles(CloseableIterator<FileStatus> scanFileIter,
                                                      StructType physicalSchema,
                                                      java.util.Optional<Predicate> predicate)
                                               throws java.io.IOException

Description copied from interface: JsonHandler

Read and parse the JSON format file at given locations and return the data as a ColumnarBatch with the columns requested by physicalSchema.

Specified by:

readJsonFiles in interface JsonHandler

Parameters:

scanFileIter - Iterator of files to read data from.

physicalSchema - Select list of columns to read from the JSON file.

predicate - Optional predicate which the JSON reader can optionally use to prune rows that don't satisfy the predicate. Because pruning is optional and may be incomplete, caller is still responsible apply the predicate on the data returned by this method.

Returns:

an iterator of ColumnarBatchs containing the data in columnar format. It is the responsibility of the caller to close the iterator. The data returned is in the same as the order of files given in scanFileIter

Throws:

java.io.IOException - if an I/O error occurs during the read.

writeJsonFileAtomically

public void writeJsonFileAtomically(String filePath,
                                    CloseableIterator<Row> data,
                                    boolean overwrite)
                             throws java.io.IOException

Makes use of LogStore implementations in `delta-storage` to atomically write the data to a file depending upon the destination filesystem.

Specified by:

writeJsonFileAtomically in interface JsonHandler

Parameters:

filePath - Destination file path

data - Data to write as Json

overwrite - If true, the file is overwritten if it already exists. If false and a file exists FileAlreadyExistsException is thrown.

Throws:

java.io.IOException

java.nio.file.FileAlreadyExistsException - if the file already exists and overwrite is false.