SQLAlchemy 中的条件过滤 [英] Conditionally Filtering in SQLAlchemy

问题描述

有没有办法有条件地将 filter 参数添加到 SQL Alchemy ORM 中的查询中?

Is there a way to conditionally add filter arguments to a query in the SQL Alchemy ORM?

例如想象一下，我有以下内容:

For example imagine, I have the following:

q = session.query(X)
if a:
 q.filter(X.y == 'a')
elif b:
 q.filter(X.y == 'a', X.z == 'b')
elif c:
 q.filter(X.y == 'a', X.p == 'd') 

有没有办法说只是添加

X.z == 'b' if b

无需在每个过滤器中读取 (X.y == 'a').

without having to readd (X.y == 'a') in every filter.

看来我可以做到

q.filter(X.y == 'a').filter(X.y == 'b')

但这会改变正在执行的查询.

but this changes the query that is being performed.

推荐答案

尝试将您的查询收集到一个列表中，然后在调用 filter 时使用 * 运算符:

Try collecting your queries into a list, and then use the * operator when you call filter:

queries = [X.y == 'a']
if b:
    queries.append(X.z == 'b')
q.filter(*queries)

顺便说一句，我不明白为什么你认为链接两个 filter 会改变你的查询，它对应于 Xy = a AND Xz = b 就像你一样使用 filter(Xy == 'a', Xz == 'b').

And BTW I don't understand why you think chaining two filters would change your query, it would correspond to X.y = a AND X.z = b like when you use filter(X.y == 'a', X.z == 'b').

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