[GitHub] [spark] gatorsmile commented on issue #26978: [SPARK-29721][SQL] Prune unnecessary nested fields from Generate without Project

[GitBox <gi...@apache.org>]

gatorsmile commented on issue #26978: [SPARK-29721][SQL] Prune unnecessary nested fields from Generate without Project
URL: https://github.com/apache/spark/pull/26978#issuecomment-583798709
 
 
   ```
       withTable("persisted") {
         val jsonStr = """{
            "items": [
              {"itemId": 1, "itemData": "a"},
              {"itemId": 2, "itemData": "b"}
            ]
           }"""
         val df = spark.read.json(Seq(jsonStr).toDS)
         df.write.format("parquet").mode("overwrite").saveAsTable("persisted")
   
         val read = spark.table("persisted")
         spark.conf.set("spark.sql.optimizer.nestedSchemaPruning.enabled", true)
         read.select(explode_outer($"items.itemId"), $"items.itemData").explain(true)
       }
   ```
   
   Try the above example. @dongjoon-hyun @viirya 

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