hacky script to make a subset of a table's rows match those on another database

gistfile1.py

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker


FROM = 'postgresql://master/master'
TO   = 'postgresql://core/core'


sfrom = sessionmaker(bind=create_engine(FROM, client_encoding='utf-8'))()
sto   = sessionmaker(bind=create_engine(TO,   client_encoding='utf-8'))()


def utfish(values):
    result = {}
    for k in values.keys():
        val = values[k]
        if isinstance(val, str):
            val = val.decode('utf-8')
        result[k] = val
    return result


def match(sfrom, sto, key, tbl, filter):

    # backup first!
    sto.execute("create table kevin_backup_%s as select * from %s" % (
        tbl, tbl))

    rows = sfrom.execute("select * from %s %s" % (tbl, filter))
    for row in rows:
        values = utfish(row)
        print values[key]
        dest = sto.execute("select * from %s where %s=:key" % (tbl, key),
                {'key': values[key]}).first()
        if not dest:
            qry = 'insert into %s (%s) values (%s)' % (
                    tbl,
                    ', '.join(k for k in row.keys()),
                    ', '.join(':' + k for k in row.keys()))
            print qry
            sto.execute(qry, utfish(row))
        else:
            qry = 'update %s set %s where %s=:%s' % (
                    tbl,
                    ', '.join('%s=:%s' % (k, k) for k in row.keys()),
                    key,
                    key)
            print qry
            sto.execute(qry, utfish(row))

    rows = sto.execute("select * from %s %s" % (tbl, filter))
    for row in rows:
        values = utfish(row)
        print values[key]
        dest = sfrom.execute("select * from %s where %s=:key" % (tbl, key),
                {'key': values[key]}).first()
        if not dest:
            try:
                sto.execute("delete from %s where %s=:key" % (tbl, key),
                        {'key': row[key]})
            except:
                sto.rollback()

match(sfrom, sto, 'template_id', 'template',
    'where account_id = 0 and template_collection_id is not null')
sfrom.rollback()
sto.commit()