[GitHub] [arrow-datafusion] alamb commented on pull request #2642: Implement DESCRIBE

alamb commented on PR #2642:
URL: https://github.com/apache/arrow-datafusion/pull/2642#issuecomment-1141107090

   >  Hi @alamb, thanks for your review, currently this PR only implements describe table_name, the describe table table_name is not implemented, this is why your test case has an error, should I also implement the describe table table_name?
   
   🤦  -- no sorry @LiuYuHui  I was mistaken on the syntax of `describe` -- no need to implement `describe table foo`
   
   I tried the correct syntax and it works great 👍 
   ```sql
   ❯ describe y;
   +-------------+-----------+-------------+
   | column_name | data_type | is_nullable |
   +-------------+-----------+-------------+
   | column1     | Int64     | YES         |
   | column2     | Int64     | YES         |
   +-------------+-----------+-------------+
   2 rows in set. Query took 0.006 seconds.
   ```
   
   However, I do think this PR needs a test. 
   
   Also, would it be possible to generate an error if the table didn't exist?
   
   For example, mysql does the following for a non existent table:
   
   ```sql
   mysql> describe ff;
   ERROR 1146 (42S02): Table 'foo.ff' doesn't exist
   ```
   
   But this PR returns an empty row:
   
   
   ```sql
   ❯ describe table;
   0 rows in set. Query took 0.020 seconds.
   ```
   
   


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