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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.sql.execution.datasources.json
import java.util.Comparator
import com.fasterxml.jackson.core._
import org.apache.spark.SparkException
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.catalyst.analysis.TypeCoercion
import org.apache.spark.sql.catalyst.json.JacksonUtils.nextUntil
import org.apache.spark.sql.catalyst.json.JSONOptions
import org.apache.spark.sql.catalyst.util.{DropMalformedMode, FailFastMode, ParseMode, PermissiveMode}
import org.apache.spark.sql.types._
import org.apache.spark.util.Utils
private[sql] object JsonInferSchema {
/**
* Infer the type of a collection of json records in three stages:
* 1. Infer the type of each record
* 2. Merge types by choosing the lowest type necessary to cover equal keys
* 3. Replace any remaining null fields with string, the top type
*/
def infer[T](
json: RDD[T],
configOptions: JSONOptions,
createParser: (JsonFactory, T) => JsonParser): StructType = {
val parseMode = configOptions.parseMode
val columnNameOfCorruptRecord = configOptions.columnNameOfCorruptRecord
// perform schema inference on each row and merge afterwards
val rootType = json.mapPartitions { iter =>
val factory = new JsonFactory()
configOptions.setJacksonOptions(factory)
iter.flatMap { row =>
try {
Utils.tryWithResource(createParser(factory, row)) { parser =>
parser.nextToken()
Some(inferField(parser, configOptions))
}
} catch {
case e @ (_: RuntimeException | _: JsonProcessingException) => parseMode match {
case PermissiveMode =>
Some(StructType(Seq(StructField(columnNameOfCorruptRecord, StringType))))
case DropMalformedMode =>
None
case FailFastMode =>
throw new SparkException("Malformed records are detected in schema inference. " +
s"Parse Mode: ${FailFastMode.name}.", e)
}
}
}
}.fold(StructType(Nil))(
compatibleRootType(columnNameOfCorruptRecord, parseMode))
canonicalizeType(rootType) match {
case Some(st: StructType) => st
case _ =>
// canonicalizeType erases all empty structs, including the only one we want to keep
StructType(Nil)
}
}
private[this] val structFieldComparator = new Comparator[StructField] {
override def compare(o1: StructField, o2: StructField): Int = {
o1.name.compareTo(o2.name)
}
}
private def isSorted(arr: Array[StructField]): Boolean = {
var i: Int = 0
while (i < arr.length - 1) {
if (structFieldComparator.compare(arr(i), arr(i + 1)) > 0) {
return false
}
i += 1
}
true
}
/**
* Infer the type of a json document from the parser's token stream
*/
private def inferField(parser: JsonParser, configOptions: JSONOptions): DataType = {
import com.fasterxml.jackson.core.JsonToken._
parser.getCurrentToken match {
case null | VALUE_NULL => NullType
case FIELD_NAME =>
parser.nextToken()
inferField(parser, configOptions)
case VALUE_STRING if parser.getTextLength < 1 =>
// Zero length strings and nulls have special handling to deal
// with JSON generators that do not distinguish between the two.
// To accurately infer types for empty strings that are really
// meant to represent nulls we assume that the two are isomorphic
// but will defer treating null fields as strings until all the
// record fields' types have been combined.
NullType
case VALUE_STRING => StringType
case START_OBJECT =>
val builder = Array.newBuilder[StructField]
while (nextUntil(parser, END_OBJECT)) {
builder += StructField(
parser.getCurrentName,
inferField(parser, configOptions),
nullable = true)
}
val fields: Array[StructField] = builder.result()
// Note: other code relies on this sorting for correctness, so don't remove it!
java.util.Arrays.sort(fields, structFieldComparator)
StructType(fields)
case START_ARRAY =>
// If this JSON array is empty, we use NullType as a placeholder.
// If this array is not empty in other JSON objects, we can resolve
// the type as we pass through all JSON objects.
var elementType: DataType = NullType
while (nextUntil(parser, END_ARRAY)) {
elementType = compatibleType(
elementType, inferField(parser, configOptions))
}
ArrayType(elementType)
case (VALUE_NUMBER_INT | VALUE_NUMBER_FLOAT) if configOptions.primitivesAsString => StringType
case (VALUE_TRUE | VALUE_FALSE) if configOptions.primitivesAsString => StringType
case VALUE_NUMBER_INT | VALUE_NUMBER_FLOAT =>
import JsonParser.NumberType._
parser.getNumberType match {
// For Integer values, use LongType by default.
case INT | LONG => LongType
// Since we do not have a data type backed by BigInteger,
// when we see a Java BigInteger, we use DecimalType.
case BIG_INTEGER | BIG_DECIMAL =>
val v = parser.getDecimalValue
if (Math.max(v.precision(), v.scale()) <= DecimalType.MAX_PRECISION) {
DecimalType(Math.max(v.precision(), v.scale()), v.scale())
} else {
DoubleType
}
case FLOAT | DOUBLE if configOptions.prefersDecimal =>
val v = parser.getDecimalValue
if (Math.max(v.precision(), v.scale()) <= DecimalType.MAX_PRECISION) {
DecimalType(Math.max(v.precision(), v.scale()), v.scale())
} else {
DoubleType
}
case FLOAT | DOUBLE =>
DoubleType
}
case VALUE_TRUE | VALUE_FALSE => BooleanType
}
}
/**
* Convert NullType to StringType and remove StructTypes with no fields
*/
private def canonicalizeType(tpe: DataType): Option[DataType] = tpe match {
case at @ ArrayType(elementType, _) =>
for {
canonicalType <- canonicalizeType(elementType)
} yield {
at.copy(canonicalType)
}
case StructType(fields) =>
val canonicalFields: Array[StructField] = for {
field <- fields
if field.name.length > 0
canonicalType <- canonicalizeType(field.dataType)
} yield {
field.copy(dataType = canonicalType)
}
if (canonicalFields.length > 0) {
Some(StructType(canonicalFields))
} else {
// per SPARK-8093: empty structs should be deleted
None
}
case NullType => Some(StringType)
case other => Some(other)
}
private def withCorruptField(
struct: StructType,
other: DataType,
columnNameOfCorruptRecords: String,
parseMode: ParseMode) = parseMode match {
case PermissiveMode =>
// If we see any other data type at the root level, we get records that cannot be
// parsed. So, we use the struct as the data type and add the corrupt field to the schema.
if (!struct.fieldNames.contains(columnNameOfCorruptRecords)) {
// If this given struct does not have a column used for corrupt records,
// add this field.
val newFields: Array[StructField] =
StructField(columnNameOfCorruptRecords, StringType, nullable = true) +: struct.fields
// Note: other code relies on this sorting for correctness, so don't remove it!
java.util.Arrays.sort(newFields, structFieldComparator)
StructType(newFields)
} else {
// Otherwise, just return this struct.
struct
}
case DropMalformedMode =>
// If corrupt record handling is disabled we retain the valid schema and discard the other.
struct
case FailFastMode =>
// If `other` is not struct type, consider it as malformed one and throws an exception.
throw new SparkException("Malformed records are detected in schema inference. " +
s"Parse Mode: ${FailFastMode.name}. Reasons: Failed to infer a common schema. " +
s"Struct types are expected, but `${other.catalogString}` was found.")
}
/**
* Remove top-level ArrayType wrappers and merge the remaining schemas
*/
private def compatibleRootType(
columnNameOfCorruptRecords: String,
parseMode: ParseMode): (DataType, DataType) => DataType = {
// Since we support array of json objects at the top level,
// we need to check the element type and find the root level data type.
case (ArrayType(ty1, _), ty2) =>
compatibleRootType(columnNameOfCorruptRecords, parseMode)(ty1, ty2)
case (ty1, ArrayType(ty2, _)) =>
compatibleRootType(columnNameOfCorruptRecords, parseMode)(ty1, ty2)
// Discard null/empty documents
case (struct: StructType, NullType) => struct
case (NullType, struct: StructType) => struct
case (struct: StructType, o) if !o.isInstanceOf[StructType] =>
withCorruptField(struct, o, columnNameOfCorruptRecords, parseMode)
case (o, struct: StructType) if !o.isInstanceOf[StructType] =>
withCorruptField(struct, o, columnNameOfCorruptRecords, parseMode)
// If we get anything else, we call compatibleType.
// Usually, when we reach here, ty1 and ty2 are two StructTypes.
case (ty1, ty2) => compatibleType(ty1, ty2)
}
private[this] val emptyStructFieldArray = Array.empty[StructField]
/**
* Returns the most general data type for two given data types.
*/
def compatibleType(t1: DataType, t2: DataType): DataType = {
TypeCoercion.findTightestCommonType(t1, t2).getOrElse {
// t1 or t2 is a StructType, ArrayType, or an unexpected type.
(t1, t2) match {
// Double support larger range than fixed decimal, DecimalType.Maximum should be enough
// in most case, also have better precision.
case (DoubleType, _: DecimalType) | (_: DecimalType, DoubleType) =>
DoubleType
case (t1: DecimalType, t2: DecimalType) =>
val scale = math.max(t1.scale, t2.scale)
val range = math.max(t1.precision - t1.scale, t2.precision - t2.scale)
if (range + scale > 38) {
// DecimalType can't support precision > 38
DoubleType
} else {
DecimalType(range + scale, scale)
}
case (StructType(fields1), StructType(fields2)) =>
// Both fields1 and fields2 should be sorted by name, since inferField performs sorting.
// Therefore, we can take advantage of the fact that we're merging sorted lists and skip
// building a hash map or performing additional sorting.
assert(isSorted(fields1), s"StructType's fields were not sorted: ${fields1.toSeq}")
assert(isSorted(fields2), s"StructType's fields were not sorted: ${fields2.toSeq}")
val newFields = new java.util.ArrayList[StructField]()
var f1Idx = 0
var f2Idx = 0
while (f1Idx < fields1.length && f2Idx < fields2.length) {
val f1Name = fields1(f1Idx).name
val f2Name = fields2(f2Idx).name
val comp = f1Name.compareTo(f2Name)
if (comp == 0) {
val dataType = compatibleType(fields1(f1Idx).dataType, fields2(f2Idx).dataType)
newFields.add(StructField(f1Name, dataType, nullable = true))
f1Idx += 1
f2Idx += 1
} else if (comp < 0) { // f1Name < f2Name
newFields.add(fields1(f1Idx))
f1Idx += 1
} else { // f1Name > f2Name
newFields.add(fields2(f2Idx))
f2Idx += 1
}
}
while (f1Idx < fields1.length) {
newFields.add(fields1(f1Idx))
f1Idx += 1
}
while (f2Idx < fields2.length) {
newFields.add(fields2(f2Idx))
f2Idx += 1
}
StructType(newFields.toArray(emptyStructFieldArray))
case (ArrayType(elementType1, containsNull1), ArrayType(elementType2, containsNull2)) =>
ArrayType(compatibleType(elementType1, elementType2), containsNull1 || containsNull2)
// The case that given `DecimalType` is capable of given `IntegralType` is handled in
// `findTightestCommonTypeOfTwo`. Both cases below will be executed only when
// the given `DecimalType` is not capable of the given `IntegralType`.
case (t1: IntegralType, t2: DecimalType) =>
compatibleType(DecimalType.forType(t1), t2)
case (t1: DecimalType, t2: IntegralType) =>
compatibleType(t1, DecimalType.forType(t2))
// strings and every string is a Json object.
case (_, _) => StringType
}
}
}
}
