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From oripwk <ori....@gmail.com>
Subject Re: Cannot read case-sensitive Glue table backed by Parquet
Date Fri, 17 Jan 2020 14:31:26 GMT
Sorry, but my original solution is incorrect

1. Glue Crawlers are not supposed to set the spark.sql.sources.schema.*
properties, but Spark SQL should. The default in Spark 2.4 for
spark.sql.hive.caseSensitiveInferenceMode is INFER_AND_SAVE which means that
Spark infers the schema from the underlying files and alters the tables to
add the spark.sql.sources.schema.* properties to SERDEPROPERTIES. In our
case, Spark failed to do so, because of a I"llegalArgumentException: Can not
create a Path from an empty string" exception which is caused because the
Hive database class instance has an empty locationUri property string. This
is caused because the Glue database does not have a Location property enter
image description here. After the schema is saved, Spark reads it from the
table.
2. There could be a way around this, by setting INFER_ONLY, which should
only infer the schema from the files and not attempt to alter the table
SERDEPROPERTIES. However, this doesn't work because of a Spark bug, where
the inferred schema is then lowercased [1].

[1]
https://github.com/apache/spark/blob/c1b6fe479649c482947dfce6b6db67b159bd78a3/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala#L284




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