[SPARK-25406][SQL] For ParquetSchemaPruningSuite.scala, move calls to withSQLConf inside calls to test

(Link to Jira: https://issues.apache.org/jira/browse/SPARK-25406)

## What changes were proposed in this pull request?

The current use of `withSQLConf` in `ParquetSchemaPruningSuite.scala` is incorrect. The desired configuration settings are not being set when running the test cases.

This PR fixes that defective usage and addresses the test failures that were previously masked by that defect.

## How was this patch tested?

I added code to relevant test cases to print the expected SQL configuration settings and found that the settings were not being set as expected. When I changed the order of calls to `test` and `withSQLConf` I found that the configuration settings were being set as expected.

Closes #22394 from mallman/spark-25406-fix_broken_schema_pruning_tests.

Authored-by: Michael Allman <msa@allman.ms>
Signed-off-by: DB Tsai <d_tsai@apple.com>

Author: mallman

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaPruningSuite.scala

@@ -218,20 +218,24 @@ class ParquetSchemaPruningSuite
   }
 
   private def testSchemaPruning(testName: String)(testThunk: => Unit) {
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true") {
-      test(s"Spark vectorized reader - without partition data column - $testName") {
+    test(s"Spark vectorized reader - without partition data column - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true") {
         withContacts(testThunk)
       }
-      test(s"Spark vectorized reader - with partition data column - $testName") {
+    }
+    test(s"Spark vectorized reader - with partition data column - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true") {
         withContactsWithDataPartitionColumn(testThunk)
       }
     }
 
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
-      test(s"Parquet-mr reader - without partition data column - $testName") {
+    test(s"Parquet-mr reader - without partition data column - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
         withContacts(testThunk)
       }
-      test(s"Parquet-mr reader - with partition data column - $testName") {
+    }
+    test(s"Parquet-mr reader - with partition data column - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false") {
         withContactsWithDataPartitionColumn(testThunk)
       }
     }
@@ -271,7 +275,7 @@ class ParquetSchemaPruningSuite
     MixedCase(1, "r1c1", MixedCaseColumn("123", 2)) ::
     Nil
 
-  testMixedCasePruning("select with exact column names") {
+  testExactCaseQueryPruning("select with exact column names") {
     val query = sql("select CoL1, coL2.B from mixedcase")
     checkScan(query, "struct<CoL1:string,coL2:struct<B:int>>")
     checkAnswer(query.orderBy("id"),
@@ -280,7 +284,7 @@ class ParquetSchemaPruningSuite
       Nil)
   }
 
-  testMixedCasePruning("select with lowercase column names") {
+  testMixedCaseQueryPruning("select with lowercase column names") {
     val query = sql("select col1, col2.b from mixedcase")
     checkScan(query, "struct<CoL1:string,coL2:struct<B:int>>")
     checkAnswer(query.orderBy("id"),
@@ -289,7 +293,7 @@ class ParquetSchemaPruningSuite
       Nil)
   }
 
-  testMixedCasePruning("select with different-case column names") {
+  testMixedCaseQueryPruning("select with different-case column names") {
     val query = sql("select cOL1, cOl2.b from mixedcase")
     checkScan(query, "struct<CoL1:string,coL2:struct<B:int>>")
     checkAnswer(query.orderBy("id"),
@@ -298,34 +302,43 @@ class ParquetSchemaPruningSuite
       Nil)
   }
 
-  testMixedCasePruning("filter with different-case column names") {
+  testMixedCaseQueryPruning("filter with different-case column names") {
     val query = sql("select id from mixedcase where Col2.b = 2")
     checkScan(query, "struct<id:int,coL2:struct<B:int>>")
     checkAnswer(query.orderBy("id"), Row(1) :: Nil)
   }
 
-  private def testMixedCasePruning(testName: String)(testThunk: => Unit) {
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true",
-      SQLConf.CASE_SENSITIVE.key -> "true") {
-      test(s"Spark vectorized reader - case-sensitive parser - mixed-case schema - $testName") {
-          withMixedCaseData(testThunk)
+  // Tests schema pruning for a query whose column and field names are exactly the same as the table
+  // schema's column and field names. N.B. this implies that `testThunk` should pass using either a
+  // case-sensitive or case-insensitive query parser
+  private def testExactCaseQueryPruning(testName: String)(testThunk: => Unit) {
+    test(s"Spark vectorized reader - case-sensitive parser - mixed-case schema - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true",
+        SQLConf.CASE_SENSITIVE.key -> "true") {
+        withMixedCaseData(testThunk)
       }
     }
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false",
-      SQLConf.CASE_SENSITIVE.key -> "false") {
-      test(s"Parquet-mr reader - case-insensitive parser - mixed-case schema - $testName") {
+    test(s"Parquet-mr reader - case-sensitive parser - mixed-case schema - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false",
+        SQLConf.CASE_SENSITIVE.key -> "true") {
         withMixedCaseData(testThunk)
       }
     }
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true",
-      SQLConf.CASE_SENSITIVE.key -> "false") {
-      test(s"Spark vectorized reader - case-insensitive parser - mixed-case schema - $testName") {
-          withMixedCaseData(testThunk)
+    testMixedCaseQueryPruning(testName)(testThunk)
+  }
+
+  // Tests schema pruning for a query whose column and field names may differ in case from the table
+  // schema's column and field names
+  private def testMixedCaseQueryPruning(testName: String)(testThunk: => Unit) {
+    test(s"Spark vectorized reader - case-insensitive parser - mixed-case schema - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "true",
+        SQLConf.CASE_SENSITIVE.key -> "false") {
+        withMixedCaseData(testThunk)
       }
     }
-    withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false",
-      SQLConf.CASE_SENSITIVE.key -> "true") {
-      test(s"Parquet-mr reader - case-sensitive parser - mixed-case schema - $testName") {
+    test(s"Parquet-mr reader - case-insensitive parser - mixed-case schema - $testName") {
+      withSQLConf(SQLConf.PARQUET_VECTORIZED_READER_ENABLED.key -> "false",
+        SQLConf.CASE_SENSITIVE.key -> "false") {
         withMixedCaseData(testThunk)
       }
     }