fix cast failed in search field of VARCHAR2 in oracle

[pedia]

A field in Oracle table declared as:

DESCRIPTION VARCHAR2(2048 BYTE)

Access db code like:

from sqlalchemy.dialects.oracle import VARCHAR2

description = Column(VARCHAR2(2048), nullable=True)

# add this in admin.py
column_searchable_list = ('description',)

exception caught in search:

sqlalchemy.exc.DatabaseError: (cx_Oracle.DatabaseError) ORA-00906: missing left parenthesis [SQL: SELECT count(:count_2) AS count_1 FROM t_event_log WHERE lower(CAST(t_event_log.description AS VARCHAR2)) LIKE lower(:param_1)] [parameters: {'count_2': '*', 'param_1': '%100003%'}] (Background on this error at: http://sqlalche.me/e/4xp6)

The SQL should be

CAST(t_event_log.description AS VARCHAR2(2048))

'(2048)' is missing in SQL which cause error.

This PR fixed this.

[pedia]

@mrjoes Would you please review this PR?

[mrjoes]

Unfortunately, I can't merge this as-is, as it will break compatibility with non-string types that require forced conversion into a string for LIKE to work. This is a main reason why the CAST is made.

I'm not sure what's the right solution here for Oracle if Oracle always wants a length of a string in a string type.

[pedia]

@mrjoes

Take a look at the closed issue from sqlalchemy?

I think

cast(field, field.type)

is more reasonable than:

cast(field, String)

This PR only fixed error for:

column_searchable_list = ('description',)

and there is no more harmful for

column_searchable_list = ('an int field',)

[mrjoes]

Got it. I will have to run the test, because I doubt that LIKE would work when field is casted to an INT explicitly.