[GitHub] dilipbiswal opened a new pull request #23883: [SPARK-26982][SQL] Enhance describe frame work to describe the output of a query.

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

dilipbiswal opened a new pull request #23883: [SPARK-26982][SQL] Enhance describe frame work to describe the output of a query.
URL: https://github.com/apache/spark/pull/23883
 
 
   ## What changes were proposed in this pull request?
   Currently we can use `df.printSchema` to discover the schema information for a query. We should have a way to describe the output schema of a query using SQL interface. 
   
    
   
   Example:
   
   DESCRIBE SELECT * FROM desc_table
   DESCRIBE QUERY SELECT * FROM desc_table
   ```SQL
   
   spark-sql> create table desc_table (c1 int comment 'c1-comment', c2 decimal comment 'c2-comment', c3 string);
   
   spark-sql> desc select * from desc_table;
   c1	int	        c1-comment
   c2	decimal(10,0)	c2-comment
   c3	string	        NULL
   
   ```
   ## How was this patch tested?
   Added a new test under SQLQueryTestSuite and SparkSqlParserSuite

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