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Include an implementation of any of the necessary magic methods ( _eq_, _add_, etc.). You’d want to use in queries ( =, +, etc.) would cease to work, because the new comparator_factory wouldn’t We need to remember about deriving it from the original one, too.
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comparator_factory ): def regexp ( self, other ): #. So in order to add regexp and other methods to all String columns, our new string type must define its ownĬlass String ( _String ): class comparator_factory ( _String. We can both modify the behavior of existing operators, as well as introduce completely new ones. Thankfully, there is an intermediate mechanism which SQLAlchemy introduced precisely to address the need we’ve got here.Ĭomparator_factory: a kind of mixin class whose methods are incorporated into columns of that type. Meaningful for string columns, but putting them there would expose them to all columns, regardless of type! On the other hand, though, we obviously don’t want to mess with the Column class itself.
#Regular expression not filtering @ code#
Extending them with additional methods won’t do much good, because regular code In SQLAlchemy, objects like String or Integer do not represent columns of certain type In essence, what we want to do is to enhance the String column type with additional comparators, which will thenīe usable as arguments for the Query.filter method.Īs an example, consider the following model class with a string column:įrom sqlalchemy import String as _String class String ( _String ): """Enhanced version of the standard string type.""" def regexp ( self, value ): # hmm.īut this won’t actually work. It’ll be easy enough to provide the necessary support in Python. Regular expressions are not implemented there directly, “unit” tests 1, we will also add support for that backend. Since it’s a common practice to use an in-memory SQLite for running database-involved It includes four operators: for case sensitive or insensitive matching, in regular or negated versions. We will use the Postgres syntax of POSIX regular expression matchersĪs a reference. On supported database backends, it will allow for powerful I’m going to take advantage of both of these qualities here, and show how you can implement supportįor regular expression operators in query filters.