sunchao commented on a change in pull request #34199:
URL: https://github.com/apache/spark/pull/34199#discussion_r741271037



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetColumn.scala
##########
@@ -0,0 +1,68 @@
+/*
+ * 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.parquet
+
+import scala.collection.mutable
+
+import org.apache.parquet.column.ColumnDescriptor
+import org.apache.parquet.io.{ColumnIOUtil, GroupColumnIO, PrimitiveColumnIO}
+import org.apache.parquet.schema.Type.Repetition
+
+import org.apache.spark.sql.types.DataType
+
+/**
+ * Rich information for a Parquet column together with its SparkSQL type.
+ */
+case class ParquetColumn(
+    sparkType: DataType,
+    descriptor: Option[ColumnDescriptor], // only set when this is a primitive 
column
+    repetitionLevel: Int,
+    definitionLevel: Int,
+    required: Boolean,
+    path: Seq[String],
+    children: Seq[ParquetColumn]) {
+
+  def isPrimitive: Boolean = descriptor.nonEmpty
+
+  /**
+   * Returns all the leaves (i.e., primitive columns) of this, in depth-first 
order.
+   */
+  def leaves: Seq[ParquetColumn] = {
+    val buffer = mutable.ArrayBuffer[ParquetColumn]()
+    leaves0(buffer)
+    buffer.toSeq
+  }
+
+  private def leaves0(buffer: mutable.ArrayBuffer[ParquetColumn]): Unit = {
+    children.foreach(_.leaves0(buffer))
+  }
+}

Review comment:
       Oops my bad. I don't think we need this method yet so I'll remove it 
here.

##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaConverter.scala
##########
@@ -43,57 +41,128 @@ import org.apache.spark.sql.types._
  *        [[StringType]] fields.
  * @param assumeInt96IsTimestamp Whether unannotated INT96 fields should be 
assumed to be Spark SQL
  *        [[TimestampType]] fields.
+ * @param caseSensitive Whether use case sensitive analysis when comparing 
Spark catalyst read
+ *                      schema with Parquet schema
  */
 class ParquetToSparkSchemaConverter(
     assumeBinaryIsString: Boolean = 
SQLConf.PARQUET_BINARY_AS_STRING.defaultValue.get,
-    assumeInt96IsTimestamp: Boolean = 
SQLConf.PARQUET_INT96_AS_TIMESTAMP.defaultValue.get) {
+    assumeInt96IsTimestamp: Boolean = 
SQLConf.PARQUET_INT96_AS_TIMESTAMP.defaultValue.get,
+    caseSensitive: Boolean = SQLConf.CASE_SENSITIVE.defaultValue.get) {
 
   def this(conf: SQLConf) = this(
     assumeBinaryIsString = conf.isParquetBinaryAsString,
-    assumeInt96IsTimestamp = conf.isParquetINT96AsTimestamp)
+    assumeInt96IsTimestamp = conf.isParquetINT96AsTimestamp,
+    caseSensitive = conf.caseSensitiveAnalysis)
 
   def this(conf: Configuration) = this(
     assumeBinaryIsString = 
conf.get(SQLConf.PARQUET_BINARY_AS_STRING.key).toBoolean,
-    assumeInt96IsTimestamp = 
conf.get(SQLConf.PARQUET_INT96_AS_TIMESTAMP.key).toBoolean)
+    assumeInt96IsTimestamp = 
conf.get(SQLConf.PARQUET_INT96_AS_TIMESTAMP.key).toBoolean,
+    caseSensitive = conf.get(SQLConf.CASE_SENSITIVE.key).toBoolean)
 
 
   /**
    * Converts Parquet [[MessageType]] `parquetSchema` to a Spark SQL 
[[StructType]].
    */
-  def convert(parquetSchema: MessageType): StructType = 
convert(parquetSchema.asGroupType())
+  def convert(parquetSchema: MessageType): StructType = {
+    val column = new ColumnIOFactory().getColumnIO(parquetSchema)
+    val converted = convertInternal(column)
+    converted.sparkType.asInstanceOf[StructType]
+  }
 
-  private def convert(parquetSchema: GroupType): StructType = {
-    val fields = parquetSchema.getFields.asScala.map { field =>
-      field.getRepetition match {
-        case OPTIONAL =>
-          StructField(field.getName, convertField(field), nullable = true)
+  /**
+   * Convert `parquetSchema` into a [[ParquetColumn]] which contains its 
corresponding Spark
+   * SQL [[StructType]] along with other information such as the maximum 
repetition and definition
+   * level of each node, column descriptor for the leave nodes, etc.
+   *
+   * If `sparkReadSchema` is not empty, when deriving Spark SQL type from a 
Parquet field this will
+   * check if the same field also exists in the schema. If so, it will use the 
Spark SQL type.
+   * This is necessary since conversion from Parquet to Spark could cause 
precision loss. For
+   * instance, Spark read schema is smallint/tinyint but Parquet only support 
int.
+   */
+  def convertParquetColumn(
+      parquetSchema: MessageType,
+      sparkReadSchema: Option[StructType] = None): ParquetColumn = {
+    val column = new ColumnIOFactory().getColumnIO(parquetSchema)
+    convertInternal(column, sparkReadSchema)
+  }
 
-        case REQUIRED =>
-          StructField(field.getName, convertField(field), nullable = false)
+  private def convertInternal(
+      groupColumn: GroupColumnIO,
+      sparkReadSchema: Option[StructType] = None): ParquetColumn = {
+    val converted = (0 until groupColumn.getChildrenCount).map { i =>
+      val field = groupColumn.getChild(i)
+      val fieldFromReadSchema = sparkReadSchema.flatMap { schema =>
+        schema.find(f => isSameFieldName(f.name, field.getName, caseSensitive))
+      }
+      var fieldReadType = fieldFromReadSchema.map(_.dataType)
+
+      // If a field is repeated here then it is neither contained by a `LIST` 
nor `MAP`
+      // annotated group (these should've been handled in 
`convertGroupField`), e.g.:
+      //
+      //  message schema {
+      //    repeated int32 int_array;
+      //  }
+      // or
+      //  message schema {
+      //    repeated group struct_array {
+      //      optional int32 field;
+      //    }
+      //  }
+      //
+      // the corresponding Spark read type should be an array and we should 
pass the element type
+      // to the group or primitive type conversion method.
+      if (field.getType.getRepetition == REPEATED) {
+        fieldReadType = fieldReadType.flatMap {
+          case at: ArrayType => Some(at.elementType)
+          case _ =>
+            throw 
QueryCompilationErrors.illegalParquetTypeError(groupColumn.toString)
+        }
+      }
+
+      val convertedField = convertField(field, fieldReadType)
+      val fieldName = 
fieldFromReadSchema.map(_.name).getOrElse(field.getType.getName)
+
+      field.getType.getRepetition match {
+        case OPTIONAL | REQUIRED =>
+          val nullable = field.getType.getRepetition == OPTIONAL
+          (StructField(fieldName, convertedField.sparkType, nullable = 
nullable),
+              convertedField)
 
         case REPEATED =>
           // A repeated field that is neither contained by a `LIST`- or 
`MAP`-annotated group nor
           // annotated by `LIST` or `MAP` should be interpreted as a required 
list of required
           // elements where the element type is the type of the field.
-          val arrayType = ArrayType(convertField(field), containsNull = false)
-          StructField(field.getName, arrayType, nullable = false)
+          val arrayType = ArrayType(convertedField.sparkType, containsNull = 
false)
+          (StructField(fieldName, arrayType, nullable = false),
+              ParquetColumn(arrayType, None, convertedField.repetitionLevel - 
1,
+                convertedField.definitionLevel - 1, required = true, 
convertedField.path,
+                Seq(convertedField.copy(required = true))))
       }
     }
 
-    StructType(fields.toSeq)
+    ParquetColumn(StructType(converted.map(_._1)), groupColumn, 
converted.map(_._2))
   }
 
+  private def isSameFieldName(left: String, right: String, caseSensitive: 
Boolean): Boolean =
+    if (!caseSensitive) left.equalsIgnoreCase(right)
+    else left == right
+

Review comment:
       It doesn't seem easier since we also need to initialize 
`ParquetToSparkSchemaConverter` with `Configuration` which doesn't have a 
`resolver` available, so we still need to write a similar method I think.

##########
File path: 
sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java
##########
@@ -152,6 +152,7 @@ protected void initialize(String path, List<String> 
columns) throws IOException
     Configuration config = new Configuration();
     config.setBoolean(SQLConf.PARQUET_BINARY_AS_STRING().key() , false);
     config.setBoolean(SQLConf.PARQUET_INT96_AS_TIMESTAMP().key(), false);
+    config.setBoolean(SQLConf.CASE_SENSITIVE().key(), false);

Review comment:
       This path is only used for testing, so I followed the above lines to 
just set the default value for this config.

##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaConverter.scala
##########
@@ -43,57 +41,128 @@ import org.apache.spark.sql.types._
  *        [[StringType]] fields.
  * @param assumeInt96IsTimestamp Whether unannotated INT96 fields should be 
assumed to be Spark SQL
  *        [[TimestampType]] fields.
+ * @param caseSensitive Whether use case sensitive analysis when comparing 
Spark catalyst read
+ *                      schema with Parquet schema
  */
 class ParquetToSparkSchemaConverter(
     assumeBinaryIsString: Boolean = 
SQLConf.PARQUET_BINARY_AS_STRING.defaultValue.get,
-    assumeInt96IsTimestamp: Boolean = 
SQLConf.PARQUET_INT96_AS_TIMESTAMP.defaultValue.get) {
+    assumeInt96IsTimestamp: Boolean = 
SQLConf.PARQUET_INT96_AS_TIMESTAMP.defaultValue.get,
+    caseSensitive: Boolean = SQLConf.CASE_SENSITIVE.defaultValue.get) {
 
   def this(conf: SQLConf) = this(
     assumeBinaryIsString = conf.isParquetBinaryAsString,
-    assumeInt96IsTimestamp = conf.isParquetINT96AsTimestamp)
+    assumeInt96IsTimestamp = conf.isParquetINT96AsTimestamp,
+    caseSensitive = conf.caseSensitiveAnalysis)
 
   def this(conf: Configuration) = this(
     assumeBinaryIsString = 
conf.get(SQLConf.PARQUET_BINARY_AS_STRING.key).toBoolean,
-    assumeInt96IsTimestamp = 
conf.get(SQLConf.PARQUET_INT96_AS_TIMESTAMP.key).toBoolean)
+    assumeInt96IsTimestamp = 
conf.get(SQLConf.PARQUET_INT96_AS_TIMESTAMP.key).toBoolean,
+    caseSensitive = conf.get(SQLConf.CASE_SENSITIVE.key).toBoolean)
 
 
   /**
    * Converts Parquet [[MessageType]] `parquetSchema` to a Spark SQL 
[[StructType]].
    */
-  def convert(parquetSchema: MessageType): StructType = 
convert(parquetSchema.asGroupType())
+  def convert(parquetSchema: MessageType): StructType = {
+    val column = new ColumnIOFactory().getColumnIO(parquetSchema)
+    val converted = convertInternal(column)
+    converted.sparkType.asInstanceOf[StructType]
+  }
 
-  private def convert(parquetSchema: GroupType): StructType = {
-    val fields = parquetSchema.getFields.asScala.map { field =>
-      field.getRepetition match {
-        case OPTIONAL =>
-          StructField(field.getName, convertField(field), nullable = true)
+  /**
+   * Convert `parquetSchema` into a [[ParquetColumn]] which contains its 
corresponding Spark
+   * SQL [[StructType]] along with other information such as the maximum 
repetition and definition
+   * level of each node, column descriptor for the leave nodes, etc.
+   *
+   * If `sparkReadSchema` is not empty, when deriving Spark SQL type from a 
Parquet field this will
+   * check if the same field also exists in the schema. If so, it will use the 
Spark SQL type.
+   * This is necessary since conversion from Parquet to Spark could cause 
precision loss. For
+   * instance, Spark read schema is smallint/tinyint but Parquet only support 
int.
+   */
+  def convertParquetColumn(
+      parquetSchema: MessageType,
+      sparkReadSchema: Option[StructType] = None): ParquetColumn = {
+    val column = new ColumnIOFactory().getColumnIO(parquetSchema)
+    convertInternal(column, sparkReadSchema)
+  }
 
-        case REQUIRED =>
-          StructField(field.getName, convertField(field), nullable = false)
+  private def convertInternal(
+      groupColumn: GroupColumnIO,
+      sparkReadSchema: Option[StructType] = None): ParquetColumn = {
+    val converted = (0 until groupColumn.getChildrenCount).map { i =>
+      val field = groupColumn.getChild(i)
+      val fieldFromReadSchema = sparkReadSchema.flatMap { schema =>
+        schema.find(f => isSameFieldName(f.name, field.getName, caseSensitive))
+      }
+      var fieldReadType = fieldFromReadSchema.map(_.dataType)
+
+      // If a field is repeated here then it is neither contained by a `LIST` 
nor `MAP`
+      // annotated group (these should've been handled in 
`convertGroupField`), e.g.:
+      //
+      //  message schema {
+      //    repeated int32 int_array;
+      //  }
+      // or
+      //  message schema {
+      //    repeated group struct_array {
+      //      optional int32 field;
+      //    }
+      //  }
+      //
+      // the corresponding Spark read type should be an array and we should 
pass the element type
+      // to the group or primitive type conversion method.
+      if (field.getType.getRepetition == REPEATED) {
+        fieldReadType = fieldReadType.flatMap {
+          case at: ArrayType => Some(at.elementType)
+          case _ =>
+            throw 
QueryCompilationErrors.illegalParquetTypeError(groupColumn.toString)
+        }
+      }
+
+      val convertedField = convertField(field, fieldReadType)
+      val fieldName = 
fieldFromReadSchema.map(_.name).getOrElse(field.getType.getName)
+
+      field.getType.getRepetition match {
+        case OPTIONAL | REQUIRED =>
+          val nullable = field.getType.getRepetition == OPTIONAL
+          (StructField(fieldName, convertedField.sparkType, nullable = 
nullable),
+              convertedField)
 
         case REPEATED =>
           // A repeated field that is neither contained by a `LIST`- or 
`MAP`-annotated group nor
           // annotated by `LIST` or `MAP` should be interpreted as a required 
list of required
           // elements where the element type is the type of the field.
-          val arrayType = ArrayType(convertField(field), containsNull = false)
-          StructField(field.getName, arrayType, nullable = false)
+          val arrayType = ArrayType(convertedField.sparkType, containsNull = 
false)
+          (StructField(fieldName, arrayType, nullable = false),
+              ParquetColumn(arrayType, None, convertedField.repetitionLevel - 
1,
+                convertedField.definitionLevel - 1, required = true, 
convertedField.path,
+                Seq(convertedField.copy(required = true))))
       }
     }
 
-    StructType(fields.toSeq)
+    ParquetColumn(StructType(converted.map(_._1)), groupColumn, 
converted.map(_._2))
   }
 
+  private def isSameFieldName(left: String, right: String, caseSensitive: 
Boolean): Boolean =
+    if (!caseSensitive) left.equalsIgnoreCase(right)
+    else left == right
+
   /**
    * Converts a Parquet [[Type]] to a Spark SQL [[DataType]].

Review comment:
       Will update the comments here.

##########
File path: 
sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaSuite.scala
##########
@@ -114,7 +130,66 @@ abstract class ParquetSchemaTest extends ParquetTest with 
SharedSparkSession {
       sqlSchema,
       parquetSchema,
       binaryAsString,
-      int96AsTimestamp)
+      int96AsTimestamp,
+      expectedParquetColumn = expectedParquetColumn)
+  }
+
+  protected def compareParquetColumn(actual: ParquetColumn, expected: 
ParquetColumn): Unit = {
+    assert(actual.sparkType == expected.sparkType, "sparkType mismatch: " +
+        s"actual = ${actual.sparkType}, expected = ${expected.sparkType}")
+    assert(actual.descriptor === expected.descriptor, "column descriptor 
mismatch: " +
+        s"actual = ${actual.descriptor}, expected = ${expected.descriptor})")
+    // Parquet ColumnDescriptor equals only compare path so we'll need to 
compare other fields

Review comment:
       I think `path` equality is already compared above `actual.descriptor === 
expected.descriptor`? Fixed the comments.

##########
File path: 
sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaSuite.scala
##########
@@ -114,7 +130,66 @@ abstract class ParquetSchemaTest extends ParquetTest with 
SharedSparkSession {
       sqlSchema,
       parquetSchema,
       binaryAsString,
-      int96AsTimestamp)
+      int96AsTimestamp,
+      expectedParquetColumn = expectedParquetColumn)
+  }
+
+  protected def compareParquetColumn(actual: ParquetColumn, expected: 
ParquetColumn): Unit = {
+    assert(actual.sparkType == expected.sparkType, "sparkType mismatch: " +
+        s"actual = ${actual.sparkType}, expected = ${expected.sparkType}")
+    assert(actual.descriptor === expected.descriptor, "column descriptor 
mismatch: " +
+        s"actual = ${actual.descriptor}, expected = ${expected.descriptor})")
+    // Parquet ColumnDescriptor equals only compare path so we'll need to 
compare other fields

Review comment:
       I think `path` equality is already compared above via `actual.descriptor 
=== expected.descriptor`? Fixed the comments.

##########
File path: 
sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaSuite.scala
##########
@@ -114,7 +130,66 @@ abstract class ParquetSchemaTest extends ParquetTest with 
SharedSparkSession {
       sqlSchema,
       parquetSchema,
       binaryAsString,
-      int96AsTimestamp)
+      int96AsTimestamp,
+      expectedParquetColumn = expectedParquetColumn)
+  }
+
+  protected def compareParquetColumn(actual: ParquetColumn, expected: 
ParquetColumn): Unit = {
+    assert(actual.sparkType == expected.sparkType, "sparkType mismatch: " +
+        s"actual = ${actual.sparkType}, expected = ${expected.sparkType}")
+    assert(actual.descriptor === expected.descriptor, "column descriptor 
mismatch: " +
+        s"actual = ${actual.descriptor}, expected = ${expected.descriptor})")
+    // Parquet ColumnDescriptor equals only compare path so we'll need to 
compare other fields
+    // explicitly here
+    if (actual.descriptor.isDefined && expected.descriptor.isDefined) {
+      val actualDesc = actual.descriptor.get
+      val expectedDesc = expected.descriptor.get
+      assert(actualDesc.getMaxRepetitionLevel == 
expectedDesc.getMaxRepetitionLevel)

Review comment:
       It looks like a bug to me, although I don't know the history (can't find 
it either).

##########
File path: 
sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetSchemaSuite.scala
##########
@@ -902,6 +1890,181 @@ class ParquetSchemaSuite extends ParquetSchemaTest {
     """.stripMargin,
     writeLegacyParquetFormat = true)
 
+  testParquetToCatalyst(
+    "SPARK-36935: test case insensitive when converting Parquet schema",
+    StructType(Seq(StructField("F1", ShortType))),
+    """message root {
+      |  optional int32 f1;
+      |}
+      |""".stripMargin,

Review comment:
       Eh I just followed the previous test case on this..

##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRowConverter.scala
##########
@@ -609,7 +610,13 @@ private[parquet] class ParquetRowConverter(
       //
       // If the element type does not match the Catalyst type and the 
underlying repeated type
       // does not belong to the legacy LIST type, then it is case 1; 
otherwise, it is case 2.
-      val guessedElementType = schemaConverter.convertField(repeatedType)
+      //
+      // Since `convertField` method requires a Parquet `ColumnIO` as input, 
here we first create
+      // a dummy message type which wraps the given repeated type, and then 
convert it to the
+      // `ColumnIO` using Parquet API.
+      val messageType = 
Types.buildMessage().addField(repeatedType).named("foo")

Review comment:
       Hm not sure if it's necessary since the comments above already explained 
the reason and this is only the place where the dummy name is used.




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