如何使用SQLAlchemy检查PostgreSQL模式是否存在？
问题描述：
我正在使用SQLAlchemy在PostgreSQL数据库中的特定模式下生成表。如果该架构不存在，我想创建它。我知道PostgreSQL查询来检查架构是否存在：
I am using SQLAlchemy to generate tables in a specific schema in a PostgreSQL database. If the schema does not exist, I want to create it. I know the PostgreSQL query to check for the existence of the schema:
SELECT exists(select schema_name FROM information_schema.schemata WHERE schema_name = 'foo')
但我想知道如何使用SQLAlchemy处理该问题。
but I want to know how I should handle this using SQLAlchemy.
答
@javax的答案几乎是正确的；以下是一些澄清：
@javax's answer is almost correct; the following is a little clarification:
q = exists(select([("schema_name")]).select_from("information_schema.schemata")
.where("schema_name = 'foo'"))
if not session.query(q).scalar():
session.execute('CREATE SCHEMA foo;')