SQLAlchemy With Clause (CTE) with Insert 不能为 Oracle 正确编译

Question

我正在尝试在 SQLAlchemy 中为 Oracle 12CR1 数据库生成以下人为的 DML 语句：

INSERT INTO baz（名称，数量）
带条 AS (
    选择 bar.name, bar.qty
    发件人栏
)
选择 foo.name, bar.qty
FROM foo JOIN bar ON foo.name = bar.name

但是，SQLAlchemy 似乎乱序生成，如下所示：

带条 AS (
    选择 bar.name, bar.qty
    发件人栏
)
INSERT INTO baz（名称，数量）
选择 foo.name, bar.qty
FROM foo JOIN bar ON foo.name = bar.name

无序执行此操作失败并显示ORA-00923: FROM keyword not found where expected.

我的理论是，SQLAlchemy 假设 PostgreSQL 语法是WITH ... INSERT INTO ... SELECT ...并且不尊重 Oracle 语法，即INSERT INTO ... WITH ... SELECT ....

有没有办法让它与 Oracle 一起工作，或者至少有一种方法可以修改 aninsert().from_select()的编译方式？

重现：

from sqlalchemy import (Table, Column, String, Integer,
                    MetaData, select, func)
from sqlalchemy.dialects import oracle


metadata = MetaData()

foo = Table('foo', metadata, Column('name', String))
bar = Table('bar', metadata, Column('name', String), Column('qty', Integer))
baz = Table('baz', metadata, Column('name', String), Column('qty', Integer))

with_bar = select([bar.c.name, bar.c.qty]).cte('bar')
sel = select([foo.c.name, with_bar.c.qty])
sel = sel.select_from(
        foo.join(with_bar, 
                 foo.c.name == with_bar.c.name
                 )
)

ins = baz.insert().from_select([baz.c.name, baz.c.qty], sel)
print ins.compile(dialect=oracle.dialect())

Answer 1

您将需要对语句进行自定义呈现。这是帮助我在另一种方言上解决这个确切问题的代码（我已将其更改为 oracle）

from sqlalchemy.ext.compiler import compiles
from sqlalchemy.sql.expression import ClauseElement, Executable

class InsertFromSelect(Executable, ClauseElement):
    def __init__(self, table, select):
        self.table = table
        self.select = select

@compiles(InsertFromSelect, "oracle")
def visit_insert_from_select(element, compiler, **kw):
    return "INSERT INTO %s (%s)" % (
        compiler.process(element.table, asfrom=True, **kw),
        compiler.process(element.select, **kw)
    )

#target table to insert
table = sqlalchemy.Table('foo' MetaData=())
#statement with a CTE / WITH clause
baz = select().select_from(sqlalchemy.text('select * from bar').columns().cte())

#print or run the new statement, correctly ordered
print(
    InsertFromSelect(table,baz)
)

本质上，您将创建一个新元素InsertFromSelect来分别保存查询和插入，然后创建一个编译访问器将它们呈现在正确的位置。