[GitHub] [spark] cloud-fan commented on a change in pull request #16944: [SPARK-19611][SQL] Introduce configurable table schema inference

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #16944:
URL: https://github.com/apache/spark/pull/16944#discussion_r443343602



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File path: sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala
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@@ -218,6 +228,54 @@ private[hive] class HiveMetastoreCatalog(sparkSession: SparkSession) extends Log
     result.copy(expectedOutputAttributes = Some(relation.output))
   }
 
+  private def inferIfNeeded(
+      relation: CatalogRelation,
+      options: Map[String, String],
+      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.unquotedString
+    if (shouldInfer) {
+      logInfo(s"Inferring case-sensitive schema for table $tableName (inference mode: " +
+        s"$inferenceMode)")
+      val fileIndex = fileIndexOpt.getOrElse {
+        val rootPath = new Path(relation.tableMeta.location)
+        new InMemoryFileIndex(sparkSession, Seq(rootPath), options, None)
+      }
+
+      val inferredSchema = fileFormat
+        .inferSchema(
+          sparkSession,
+          options,
+          fileIndex.listFiles(Nil).flatMap(_.files))

Review comment:
       schema inference needs to look at the entire data set.




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