[GitHub] [arrow-datafusion] andygrove commented on a diff in pull request #3763: Support datetime keywords in functions

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

andygrove commented on code in PR #3763:
URL: https://github.com/apache/arrow-datafusion/pull/3763#discussion_r992828969


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datafusion/sql/src/planner.rs:
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@@ -5309,6 +5456,19 @@ mod tests {
         assert!(logical_plan("SELECT \"1\"").is_err());
     }
 
+    #[test]
+    fn test_datetime_keyword_conversion() {
+        // Field "year" does not exist in table.
+        let sql_expr = "SELECT AVG(year) FROM person";
+        let err1 = logical_plan(sql_expr).expect_err("query should have failed");
+        assert_plan_error(err1, "Avg");

Review Comment:
   > The general idea of this test is that originally, the query would have failed with a "Field Not Found" error because "year" isn't in the "person" table. 
   
   That sounds like the correct behavior to me. Here is an example from Postgres:
   
   ```
   postgres=# select avg(year) from person;
   ERROR:  column "year" does not exist
   LINE 1: select avg(year) from person;
   ```
   
   > However, because Avg is a function and "year" isn't in the table, we want to convert "year" to a datetime keyword to check if it is valid, so with my changes it fails with a "The function Avg does not support inputs of type Utf8" instead.
   
   I think it would be useful to have a test of a valid use of year as a datetime keyword, as I am not fully understanding the goal here yet.
   
   > This is a pretty roundabout way of testing the functionality, but because these changes were implemented to allow datetime keyword conversion before calling something like Timestampadd in Dask-SQL, which DataFusion does not support, this was the alternative testing method I came up with. Let me know what you think.
   
   I will ping you directly with questions about the Dask SQL requirement driving this.
   
   



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