[GitHub] [superset] kekwan commented on a change in pull request #13082: fix(sql_lab): Add custom timestamp type for literal casting for presto timestamps

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

kekwan commented on a change in pull request #13082:
URL: https://github.com/apache/superset/pull/13082#discussion_r574956996



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File path: superset/db_engine_specs/presto.py
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@@ -911,10 +912,14 @@ def where_latest_partition(  # pylint: disable=too-many-arguments
         if values is None:
             return None
 
-        column_names = {column.get("name") for column in columns or []}
+        column_names = {column.get("name") : column.get('type') for column in columns or []}
         for col_name, value in zip(col_names, values):
             if col_name in column_names:
-                query = query.where(Column(col_name) == value)
+                col_type = column_names.get(col_name)
+                if col_type == 'TIMESTAMP':

Review comment:
       Yeah, that would be ideal solution or getting Presto/Trino to support auto-casting. 
   
   I've looked into it a bit and tried a few things but couldn't get any auto-casting. I've tried to pass in the default SQLAlchemy data types e.g. `types.TIMESTAMP` to the Column object as well as using a [literal](https://docs.sqlalchemy.org/en/14/core/sqlelement.html#sqlalchemy.sql.expression.literal) clause but the default data types doesn't seem to know how to auto-cast the type of value. I'm guessing because each DB dialect casts types differently so its up to the user to cast it yourself using one of these [approaches](https://docs.sqlalchemy.org/en/13/core/custom_types.html#types-sql-value-processing) to apply SQL-level binding 
   
   I have only done this casting for 2 Trino data types `TIMESTAMP` and `DATE` in this PR since these are the most popular partition column data types for our use case. But [all of these data types ](https://trino.io/docs/current/language/types.html) besides the basic string, integer, boolean types require explicit casting so this is still an issue for other data types.




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