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https://issues.apache.org/jira/browse/SPARK-38826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17523358#comment-17523358
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Sean R. Owen commented on SPARK-38826:
--------------------------------------
Yeah I guess we can at least update the docs; I'm unclear on whether the
behavior is wrong or right
> dropFieldIfAllNull option does not work for empty JSON struct
> -------------------------------------------------------------
>
> Key: SPARK-38826
> URL: https://issues.apache.org/jira/browse/SPARK-38826
> Project: Spark
> Issue Type: Improvement
> Components: Documentation
> Affects Versions: 3.2.1
> Reporter: morvenhuang
> Priority: Trivial
>
> As stated in the doc,
> {quote}dropFieldIfAllNull
> Whether to ignore column of all null values or empty array/struct during
> schema inference.
>
> {quote}
> But when I try this,
>
> {code:java}
> String json = "{\"field1\":\"value1\", \"field2\":{}}";
> JavaSparkContext jsc = new JavaSparkContext(spark.sparkContext());
> JavaRDD<String> jrdd = jsc.parallelize(Arrays.asList(json));
> Dataset<Row> df = spark.read().option("dropFieldIfAllNull",
> "false").json(jrdd);
> df.printSchema();
> {code}
>
> I get this,
> {code:java}
> root
> |-- field1: string (nullable = true){code}
> Notice field2 is still missing even when dropFieldIfAllNull is set to false,
> so apparently, this option does not work for empty struct.
> This is due to SPARK-8093, the empty struct will be dropped anyway.
> I think we should update the doc, otherwise it would be confusing.
> I can make a patch for this.
>
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