Github user budde commented on a diff in the pull request:
https://github.com/apache/spark/pull/16944#discussion_r101460565
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala ---
@@ -296,6 +296,17 @@ object SQLConf {
.longConf
.createWithDefault(250 * 1024 * 1024)
+ val HIVE_SCHEMA_INFERENCE_MODE =
buildConf("spark.sql.hive.schemaInferenceMode")
+ .doc("Configures the action to take when a case-sensitive schema
cannot be read from a Hive " +
+ "table's properties. Valid options include INFER_AND_SAVE (infer the
case-sensitive " +
+ "schema from the underlying data files and write it back to the
table properties), " +
+ "INFER_ONLY (infer the schema but don't attempt to write it to the
table properties) and " +
+ "NEVER_INFER (fallback to using the case-insensitive metastore
schema instead of inferring).")
+ .stringConf
+ .transform(_.toUpperCase())
+ .checkValues(Set("INFER_AND_SAVE", "INFER_ONLY", "NEVER_INFER"))
+ .createWithDefault("INFER_AND_SAVE")
--- End diff --
This was proposed in #16797 but I'd like to open this for discussion.
- ```INFER_ONLY``` would mimic the pre-2.1.0 behavior.
- ```INFER_AND_SAVE``` would attempt to prevent future inferences but may
fail if the Hive client doesn't have write permissions on the metastore.
- ```NEVER_INFER``` is the current behavior in 2.1.0 which breaks support
with the tables affected by
[SPARK-19611](https://issues.apache.org/jira/browse/SPARK-19611). Users may
wish to enable this mode for tables without the table properties schema that
they know are case-insensitive.
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