simplify ext/compiler.py

[Mike Bayer]

you can make a custom compiled object just like this:

class MyThing(ClauseElement):
   pass

def _compiler_dispatch(self, compiler):
    return "mything"
MyThing._compiler_dispatch = _compiler_dispatch

the UserDefinedCompiler should simplify and not create a new UDC object upon dispatch - there's too much overhead in lookup and such. Let's have UDC just receive the parent compiler as an argument and not be stateful - statefulness will be a very rare use case and they can use the parent compiler for state if need be. let's also think about the above as a super quick "i just need a clause element that does XYZ" - just subclass ClauseElement and add a dispatch method - very convenient.

[Mike Bayer]

from sqlalchemy.sql.compiler import compiles

class MyThing(ClauseElement):
   pass

@compiles(MyThing)
def compile_thing(compiler, element):
   return "mything"

@compiles(MyThing).on('postgres')
def compile_thing(compiler, element):
   return "pg_mything"

[Mike Bayer]

this is in 0.6 and has also been backported to 0.5 for several months now.

[Mike Bayer]

Removing milestone: 0.6.0 (automated comment)