Github user MaxGekk commented on a diff in the pull request:
https://github.com/apache/spark/pull/21299#discussion_r187707287
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JsonDataSource.scala
---
@@ -99,12 +99,7 @@ object TextInputJsonDataSource extends JsonDataSource {
def inferFromDataset(json: Dataset[String], parsedOptions: JSONOptions):
StructType = {
val sampled: Dataset[String] = JsonUtils.sample(json, parsedOptions)
- val rdd: RDD[InternalRow] = sampled.queryExecution.toRdd
- val rowParser = parsedOptions.encoding.map { enc =>
- CreateJacksonParser.internalRow(enc, _: JsonFactory, _: InternalRow)
- }.getOrElse(CreateJacksonParser.internalRow(_: JsonFactory, _:
InternalRow))
-
- JsonInferSchema.infer(rdd, parsedOptions, rowParser)
+ JsonInferSchema.infer(sampled, parsedOptions,
CreateJacksonParser.string)
--- End diff --
I reran the benchmarks on your branch. There is a difference in the schema
inferring benchmarks
```
JSON schema inferring: Best/Avg Time(ms) Rate(M/s)
Per Row(ns) Relative
------------------------------------------------------------------------------------------------
No encoding 46348 / 46679 2.2
463.5 1.0X
UTF-8 is set 45651 / 45731 2.2
456.5 1.0X
```
before your changes:
```
JSON schema inferring: Best/Avg Time(ms) Rate(M/s) Per
Row(ns) Relative
--------------------------------------------------------------------------------------------
No encoding 38902 / 39282 2.6
389.0 1.0X
UTF-8 is set 56959 / 57261 1.8
569.6 0.7X
```
As I wrote above _"array-based"_ parser is faster than _"string-based"_ but
_"string-based"_ parser is faster than _"reader based"_ one.
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