SQLAlchemy 'if exists' patch

sqlalchemy_exists_patch.py

import re

from sqlalchemy.ext.compiler import compiles
from sqlalchemy.schema import CreateTable, DropTable, \
         CreateSequence, DropSequence, CreateIndex, DropIndex
from sqlalchemy.dialects.postgresql import DropEnumType

patches = (
    (CreateTable, 'visit_create_table', "^\s*CREATE TABLE", "CREATE TABLE IF NOT EXISTS"),
    (CreateIndex, 'visit_create_index', "^\s*CREATE INDEX", "CREATE INDEX IF NOT EXISTS"),
    (DropTable, 'visit_drop_table', "^\s*DROP TABLE", "DROP TABLE IF EXISTS"),
    (DropSequence, 'visit_drop_sequence', "^\s*DROP SEQUENCE", "DROP SEQUENCE IF EXISTS"),
    (DropIndex, 'visit_drop_index', "^\s*DROP INDEX", "DROP INDEX IF EXISTS"),
    (DropEnumType, 'visit_drop_enum_type', "^\s*DROP TYPE", "DROP TYPE IF EXISTS"),
    )

def create_patch(visitor, method, re_from, re_to, if_always=False):

    @compiles(visitor)
    def _if_exists_(element, compiler, **kw):
        output = getattr(compiler, method)(element, **kw)
        if if_always or element.element.info.get('ifexists'):
            output = re.sub(re_from, re_to, output, re.S)
        return output
    return _if_exists_

def enable_patches(if_always=False):
    for patch in patches:
        create_patch(*patch, if_always=if_always)

Hey, thank you!

Just enable patches using enable_patches function and you're all set. it's not the best patch, but works well.

Thanks , but how do i import the function ?