[SPARK-53183][SQL] Use Java Files.readString instead of o.a.s.sql.catalyst.util.fileToString

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to use Java 11+ java.nio.file.Files.readString instead of o.a.s.sql.catalyst.util.fileToString. In other words, this PR removes Spark's fileToString method from Spark code base.

Why are the changes needed?

Since Java 11, Files.readString exists. So, we don't need to maintain fileToString method. Note that Apache Spark always uses the default value of encoding, UTF-8.

spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/package.scala

Lines 51 to 58 in c77f316

	def fileToString(file: File, encoding: Charset = UTF_8): String = {
	val inStream = new FileInputStream(file)
	try {
	new String(ByteStreams.toByteArray(inStream), encoding)
	} finally {
	inStream.close()
	}
	}

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass the CIs.

BEFORE

$ git grep fileToString | wc -l
      22

AFTER

$ git grep fileToString | wc -l
       0

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

Hi, @zhengruifeng . Could you review this method-replacement PR if you have some time, please?

[dongjoon-hyun]

Could you review this PR when you have some time, @yaooqinn ?

[yaooqinn]

LGTM

[dongjoon-hyun]

Thank you so much. Roughly, at the first run, Java one is faster.

$ bin/spark-shell --driver-memory 12G
WARNING: Using incubator modules: jdk.incubator.vector
Using Spark's default log4j profile: org/apache/spark/log4j2-defaults.properties
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 4.1.0-preview1
      /_/

Using Scala version 2.13.16 (OpenJDK 64-Bit Server VM, Java 21.0.8)
Type in expressions to have them evaluated.
Type :help for more information.
25/08/07 19:59:09 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Spark context Web UI available at http://localhost:4040
Spark context available as 'sc' (master = local[*], app id = local-1754621949360).
Spark session available as 'spark'.

scala> spark.time(org.apache.spark.sql.catalyst.util.fileToString(new java.io.File("/tmp/1G.bin")).length)
Time taken: 523 ms
val res0: Int = 1073741824

$ bin/spark-shell --driver-memory 12G
WARNING: Using incubator modules: jdk.incubator.vector
Using Spark's default log4j profile: org/apache/spark/log4j2-defaults.properties
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 4.1.0-preview1
      /_/

Using Scala version 2.13.16 (OpenJDK 64-Bit Server VM, Java 21.0.8)
Type in expressions to have them evaluated.
Type :help for more information.
25/08/07 19:59:01 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Spark context Web UI available at http://localhost:4040
Spark context available as 'sc' (master = local[*], app id = local-1754621942077).
Spark session available as 'spark'.

scala> spark.time(java.nio.file.Files.readString(java.nio.file.Path.of("/tmp/1G.bin")).length)
Time taken: 339 ms
val res0: Int = 1073741824

[dongjoon-hyun]

The test failure is a known flaky one. Merged to master.

[zhengruifeng]

Late LGTM

[dongjoon-hyun]

Thank you, @zhengruifeng .