HyukjinKwon commented on a change in pull request #27774: [SPARK-31023][SQL]
Support foldable schemas by `from_json`
URL: https://github.com/apache/spark/pull/27774#discussion_r387358620
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExprUtils.scala
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@@ -47,14 +47,18 @@ object ExprUtils {
dataType.asInstanceOf[StructType]
}
- def evalTypeExpr(exp: Expression): DataType = exp match {
- case Literal(s, StringType) => DataType.fromDDL(s.toString)
- case e @ SchemaOfJson(_: Literal, _) =>
- val ddlSchema = e.eval(EmptyRow).asInstanceOf[UTF8String]
- DataType.fromDDL(ddlSchema.toString)
- case e => throw new AnalysisException(
- "Schema should be specified in DDL format as a string literal or output
of " +
- s"the schema_of_json function instead of ${e.sql}")
+ def evalTypeExpr(exp: Expression): DataType = {
+ if (exp.foldable) {
+ exp.eval() match {
+ case s: UTF8String if s != null => DataType.fromDDL(s.toString)
+ case _ => throw new AnalysisException(
+ s"The expression '${exp.sql}' must be evaluated to a valid string.")
+ }
+ } else {
+ throw new AnalysisException(
+ "Schema should be specified in DDL format as a string literal or
output of " +
Review comment:
literal -> foldable expression such as a literal.
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