### What changes were proposed in this pull request?
This PR is to support nested column type in Spark ORC vectorized reader. Currently ORC vectorized reader [does not support nested column type (struct, array and map)](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/orc/OrcFileFormat.scala#L138). We implemented nested column vectorized reader for FB-ORC in our internal fork of Spark. We are seeing performance improvement compared to non-vectorized reader when reading nested columns. In addition, this can also help improve the non-nested column performance when reading non-nested and nested columns together in one query.
Before this PR:
* `OrcColumnVector` is the implementation class for Spark's `ColumnVector` to wrap Hive's/ORC's `ColumnVector` to read `AtomicType` data.
After this PR:
* `OrcColumnVector` is an abstract class to keep interface being shared between multiple implementation class of orc column vectors, namely `OrcAtomicColumnVector` (for `AtomicType`), `OrcArrayColumnVector` (for `ArrayType`), `OrcMapColumnVector` (for `MapType`), `OrcStructColumnVector` (for `StructType`). So the original logic to read `AtomicType` data is moved from `OrcColumnVector` to `OrcAtomicColumnVector`. The abstract class of `OrcColumnVector` is needed here because of supporting nested column (i.e. nested column vectors).
* A utility method `OrcColumnVectorUtils.toOrcColumnVector` is added to create Spark's `OrcColumnVector` from Hive's/ORC's `ColumnVector`.
* A new user-facing config `spark.sql.orc.enableNestedColumnVectorizedReader` is added to control enabling/disabling vectorized reader for nested columns. The default value is false (i.e. disabling by default). For certain tables having deep nested columns, vectorized reader might take too much memory for each sub-column vectors, compared to non-vectorized reader. So providing a config here to work around OOM for query reading wide and deep nested columns if any. We plan to enable it by default on 3.3. Leave it disable in 3.2 in case for any unknown bugs.
### Why are the changes needed?
Improve query performance when reading nested columns from ORC file format.
Tested with locally adding a small benchmark in `OrcReadBenchmark.scala`. Seeing more than 1x run time improvement.
```
Running benchmark: SQL Nested Column Scan
Running case: Native ORC MR
Stopped after 2 iterations, 37850 ms
Running case: Native ORC Vectorized (Enabled Nested Column)
Stopped after 2 iterations, 15892 ms
Running case: Native ORC Vectorized (Disabled Nested Column)
Stopped after 2 iterations, 37954 ms
Running case: Hive built-in ORC
Stopped after 2 iterations, 35118 ms
Java HotSpot(TM) 64-Bit Server VM 1.8.0_181-b13 on Mac OS X 10.15.7
Intel(R) Core(TM) i9-9980HK CPU 2.40GHz
SQL Nested Column Scan: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
------------------------------------------------------------------------------------------------------------------------------
Native ORC MR 18706 18925 310 0.1 17839.6 1.0X
Native ORC Vectorized (Enabled Nested Column) 7625 7946 455 0.1 7271.6 2.5X
Native ORC Vectorized (Disabled Nested Column) 18415 18977 796 0.1 17561.5 1.0X
Hive built-in ORC 17469 17559 127 0.1 16660.1 1.1X
```
Benchmark:
```
nestedColumnScanBenchmark(1024 * 1024)
def nestedColumnScanBenchmark(values: Int): Unit = {
val benchmark = new Benchmark(s"SQL Nested Column Scan", values, output = output)
withTempPath { dir =>
withTempTable("t1", "nativeOrcTable", "hiveOrcTable") {
import spark.implicits._
spark.range(values).map(_ => Random.nextLong).map { x =>
val arrayOfStructColumn = (0 until 5).map(i => (x + i, s"$x" * 5))
val mapOfStructColumn = Map(
s"$x" -> (x * 0.1, (x, s"$x" * 100)),
(s"$x" * 2) -> (x * 0.2, (x, s"$x" * 200)),
(s"$x" * 3) -> (x * 0.3, (x, s"$x" * 300)))
(arrayOfStructColumn, mapOfStructColumn)
}.toDF("col1", "col2")
.createOrReplaceTempView("t1")
prepareTable(dir, spark.sql(s"SELECT * FROM t1"))
benchmark.addCase("Native ORC MR") { _ =>
withSQLConf(SQLConf.ORC_VECTORIZED_READER_ENABLED.key -> "false") {
spark.sql("SELECT SUM(SIZE(col1)), SUM(SIZE(col2)) FROM nativeOrcTable").noop()
}
}
benchmark.addCase("Native ORC Vectorized (Enabled Nested Column)") { _ =>
spark.sql("SELECT SUM(SIZE(col1)), SUM(SIZE(col2)) FROM nativeOrcTable").noop()
}
benchmark.addCase("Native ORC Vectorized (Disabled Nested Column)") { _ =>
withSQLConf(SQLConf.ORC_VECTORIZED_READER_NESTED_COLUMN_ENABLED.key -> "false") {
spark.sql("SELECT SUM(SIZE(col1)), SUM(SIZE(col2)) FROM nativeOrcTable").noop()
}
}
benchmark.addCase("Hive built-in ORC") { _ =>
spark.sql("SELECT SUM(SIZE(col1)), SUM(SIZE(col2)) FROM hiveOrcTable").noop()
}
benchmark.run()
}
}
}
```
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Added one simple test in `OrcSourceSuite.scala` to verify correctness.
Definitely need more unit tests and add benchmark here, but I want to first collect feedback before crafting more tests.
Closes#31958 from c21/orc-vector.
Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
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