Unexpected/undesirable `CAST` of date string to `VARCHAR`

• asyncpg version: 0.29.0
• PostgreSQL version: 15.7
• Python version: 3.11
• Platform: macOS 13.6
• Do you use pgbouncer?: no
• Did you install asyncpg with pip?: no (poetry)

start_date = '2024-01-01'
query.where(MyTable.datetime_col >= start_date)

This will fail:

<class 'asyncpg.exceptions.UndefinedFunctionError'>: operator does not exist: timestamp without time zone >= character varying

It seems that this is being casted as VARCHAR:

SELECT * FROM my_table WHERE datetime_col >= $1::VARCHAR

This same filter is valid in Postgres

SELECT * FROM my_table WHERE datetime_col >= '2024-01-01'

It works when using the datetime object:

start_date = dt.datetime.strptime(start_date, "%Y-%m-%d")
query.where(MyTable.datetime_col >= start_date)

Wonder if this is somewhat similar to #1169 in the sense that casting/argument handling invalidates valid SQL statements.

I'd have imagined that castings were performed in obvious and non-breaking scenarios, and scenarios where casting would be necessary, but are not obvious should be handled directly by the user. Breaking valid SQL statements seems counter intuitive IMHO.

Reproduce el caso de query.where usando asyncpg 0.29.0, PostgreSQL 15.7 y Python 3.11, comparando las entradas string y datetime. Inspecciona el SQL generado y el manejo de parámetros en torno al cast $1::VARCHAR reportado. Se considera terminado cuando se haya establecido el comportamiento esperado de la comparación de fechas y esté cubierto por una prueba de regresión, o se haya demostrado que el problema corresponde a otro lugar.