Github user ericl commented on a diff in the pull request:
https://github.com/apache/spark/pull/16944#discussion_r102843314
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala ---
@@ -161,22 +164,45 @@ private[hive] class
HiveMetastoreCatalog(sparkSession: SparkSession) extends Log
bucketSpec,
Some(partitionSchema))
+ val catalogTable = metastoreRelation.catalogTable
val logicalRelation = cached.getOrElse {
val sizeInBytes =
metastoreRelation.stats(sparkSession.sessionState.conf).sizeInBytes.toLong
val fileIndex = {
- val index = new CatalogFileIndex(
- sparkSession, metastoreRelation.catalogTable, sizeInBytes)
+ val index = new CatalogFileIndex(sparkSession, catalogTable,
sizeInBytes)
if (lazyPruningEnabled) {
index
} else {
index.filterPartitions(Nil) // materialize all the
partitions in memory
}
}
val partitionSchemaColumnNames =
partitionSchema.map(_.name.toLowerCase).toSet
- val dataSchema =
- StructType(metastoreSchema
- .filterNot(field =>
partitionSchemaColumnNames.contains(field.name.toLowerCase)))
+ val filteredMetastoreSchema = StructType(metastoreSchema
+ .filterNot(field =>
partitionSchemaColumnNames.contains(field.name.toLowerCase)))
+
+ // Infer a case-sensitive schema when the metastore doesn't
return one, if configured.
+ val inferredSchema = inferSchema(
+ catalogTable,
+ metastoreSchema,
+ options,
+ defaultSource,
+ fileType,
+ fileIndex)
+
+ // If configured, save the inferred case-sensitive schema to the
table properties and
+ // fetch the updated CatalogTable record for use in the
LogicalRelation.
+ val updatedCatalogTable = updateCatalogTable(catalogTable,
inferredSchema)
+
+ val dataSchema = inferenceMode match {
+ case (INFER_AND_SAVE | INFER_ONLY) if
(!catalogTable.schemaPreservesCase) =>
+ inferredSchema.getOrElse {
+ logWarning(s"Unable to infer schema for table
$tableIdentifier from file format " +
+ s"$defaultSource (inference mode: $inferenceMode); using
metastore schema.")
+ filteredMetastoreSchema
+ }
+ case _ =>
+ filteredMetastoreSchema
+ }
--- End diff --
I'm still finding this a bit awkward to read because the inferenceMode
config flag is referenced in three separate places. How about centralizing the
logic a little, moving the config checks to the body of this function?
```
val shouldInferSchema = !catalogTable.schemaPreservesCase && inferenceMode
!= NEVER_INFER
val dataSchema = if (shouldInferSchema) {
val inferredSchema = inferSchema(...)
if (inferenceMode == INFER_AND_SAVE) {
try {
updateCatalogTableSchema(...)
} catch {
...
}
}
inferredSchema
} else {
filteredMetastoreSchema
}
```
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