對於postgres，SQLAlchemy是否支持UPDATE ..... FROM語法？

Question

我想與SQLAlchemy的編寫一個查詢，像這樣：

UPDATE mytable 
SET 
    mytext = myvalues.mytext, 
    myint = myvalues.myint 
FROM (
    VALUES 
    (1, 'textA', 99), 
    (2, 'textB', 88), 
    ... 
) AS myvalues (mykey, mytext, myint) 
WHERE mytable.mykey = myvalues.mykey 

是這種事情在ORM原生支持？或者我需要使用session.execute（）來運行原始SQL？

Answer 1

通過在郵件列表上@zzzeek：

我們做UPDATE..FROM但得到的VALUES東西在裏面需要一些額外的食譜，因爲我們沒有建在現在這個結構。也是它命名爲AS部分中的列的別名部分不是本地構建的。配方在這裏：https://bitbucket.org/zzzeek/sqlalchemy/wiki/UsageRecipes/PGValues。在某些時候，我向某人展示了AS的一部分，但那不在那裏...。我剛剛更新了它，它還需要幫助才能在UPDATE環境中工作。所以：

from sqlalchemy.ext.compiler import compiles 
from sqlalchemy.sql.expression import FromClause 

class values(FromClause): 
    named_with_column = True 

    def __init__(self, columns, *args, **kw): 
     self._column_args = columns 
     self.list = args 
     self.alias_name = self.name = kw.pop('alias_name', None) 

    def _populate_column_collection(self): 
     for c in self._column_args: 
      c._make_proxy(self) 


@compiles(values) 
def compile_values(element, compiler, asfrom=False, **kw): 
    columns = element.columns 
    v = "VALUES %s" % ", ".join(
     "(%s)" % ", ".join(
       compiler.render_literal_value(elem, column.type) 
       for elem, column in zip(tup, columns)) 
     for tup in element.list 
    ) 
    if asfrom: 
     if element.alias_name: 
      v = "(%s) AS %s (%s)" % (v, element.alias_name, (", ".join(c.name for c in element.columns))) 
     else: 
      v = "(%s)" % v 
    return v 

if __name__ == '__main__': 
    from sqlalchemy import MetaData, create_engine, String, Integer, Table, Column 
    from sqlalchemy.sql import column 
    from sqlalchemy.orm import Session, mapper 
    m1 = MetaData() 
    class T(object): 
     pass 
    t1 = Table('mytable', m1, Column('mykey', Integer, primary_key=True), 
        Column('mytext', String), 
        Column('myint', Integer)) 
    mapper(T, t1) 
    t2 = values(
      [ 
       column('mykey', Integer), 
       column('mytext', String), 
       column('myint', Integer) 
      ], 


      (1, 'textA', 99), 
      (2, 'textB', 88), 

      alias_name='myvalues' 
     ) 
    e = create_engine("postgresql://scott:tiger@localhost/test", echo=True) 
    m1.create_all(e) 
    sess = Session(e) 
    sess.query(T).filter(T.mykey==t2.c.mykey).\ 
      update(dict(mytext=t2.c.mytext, myint=t2.c.myint))