Github user budde commented on a diff in the pull request:
https://github.com/apache/spark/pull/16944#discussion_r104249293
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala ---
@@ -217,6 +235,62 @@ private[hive] class HiveMetastoreCatalog(sparkSession:
SparkSession) extends Log
result.copy(expectedOutputAttributes = Some(relation.output))
}
+ private def inferIfNeeded(
+ relation: CatalogRelation,
+ options: Map[String, String],
+ fallbackSchema: StructType,
+ fileFormat: FileFormat,
+ fileIndexOpt: Option[FileIndex] = None): (StructType, CatalogTable)
= {
+ val inferenceMode =
sparkSession.sessionState.conf.caseSensitiveInferenceMode
+ val shouldInfer = (inferenceMode != NEVER_INFER) &&
!relation.tableMeta.schemaPreservesCase
+ val tableName = relation.tableMeta.identifier.table
+ if (shouldInfer) {
+ logInfo(s"Inferring case-sensitive schema for table $tableName
(inference mode: " +
+ s"$inferenceMode)")
+ val fileIndex = fileIndexOpt.getOrElse {
+ val rootPath = new Path(new URI(relation.tableMeta.location))
+ new InMemoryFileIndex(sparkSession, Seq(rootPath), options, None)
+ }
+
+ val inferredSchema = {
+ val schema = fileFormat.inferSchema(
+ sparkSession,
+ options,
+ fileIndex.listFiles(Nil).flatMap(_.files))
+ fileFormat match {
+ case _: ParquetFileFormat =>
+
schema.map(ParquetFileFormat.mergeMetastoreParquetSchema(relation.tableMeta.schema,
_))
--- End diff --
This was used in the previous code for schema inference. I think the only
reason this would still be needed is if the metastore schema contains a
nullable field that isn't actually present in the underlying Parquet data. See
#5214 for more details here.
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