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[SPARK-19611][SQL] Preserve metastore field order when merging inferred schema #17249

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budde wants to merge 1 commit into from
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[SPARK-19611][SQL] Preserve metastore field order when merging inferred schema #17249

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5 changes: 1 addition & 4 deletions sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -356,13 +356,10 @@ private[hive] object HiveMetastoreCatalog {
.filterKeys(!inferredSchema.map(_.name.toLowerCase).contains(_))
.values
.filter(_.nullable)

// Merge missing nullable fields to inferred schema and build a case-insensitive field map.
val inferredFields = StructType(inferredSchema ++ missingNullables)
.map(f => f.name.toLowerCase -> f).toMap
StructType(metastoreFields.map { case(name, field) =>
field.copy(name = inferredFields(name).name)
}.toSeq)
StructType(metastoreSchema.map(f => f.copy(name = inferredFields(f.name).name)))
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@dongjoon-hyun dongjoon-hyun Mar 10, 2017

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I see. Now metastoreSchema is used instead of metastoreFields.

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@budde budde Mar 10, 2017

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This should ensure the proper ordering is used. Iterating over the metastoreFields map isn't guaranteed to maintain the original ordering.

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@dongjoon-hyun dongjoon-hyun Mar 10, 2017

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Yep. I'm still building this PR locally, but it looks good logically. :) I'll post my result soon.

} catch {
case NonFatal(_) =>
val msg = s"""Detected conflicting schemas when merging the schema obtained from the Hive
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21 changes: 21 additions & 0 deletions sql/hive/src/test/scala/org/apache/spark/sql/hive/HiveSchemaInferenceSuite.scala
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Expand Up @@ -293,6 +293,27 @@ class HiveSchemaInferenceSuite
StructField("firstField", StringType, nullable = true),
StructField("secondField", StringType, nullable = true))))
}.getMessage.contains("Detected conflicting schemas"))

// Schema merge should maintain metastore order.
assertResult(
StructType(Seq(
StructField("first_field", StringType, nullable = true),
StructField("second_field", StringType, nullable = true),
StructField("third_field", StringType, nullable = true),
StructField("fourth_field", StringType, nullable = true),
StructField("fifth_field", StringType, nullable = true)))) {
HiveMetastoreCatalog.mergeWithMetastoreSchema(
StructType(Seq(
StructField("first_field", StringType, nullable = true),
StructField("second_field", StringType, nullable = true),
StructField("third_field", StringType, nullable = true),
StructField("fourth_field", StringType, nullable = true),
StructField("fifth_field", StringType, nullable = true))),
StructType(Seq(
StructField("fifth_field", StringType, nullable = true),
StructField("third_field", StringType, nullable = true),
StructField("second_field", StringType, nullable = true))))
}
}
}

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