Question

createuser允许在PostgreSQL中创建用户（ROLE）。有没有一种简单的方法来检查该用户（名称）是否已经存在？否则createuser将返回错误：

createuser: creation of new role failed: ERROR:  role "USR_NAME" already exists

更新：解决方案应该可以从shell中执行，这样可以更容易地在脚本内部自动化。

Answer 1

SELECT 1 FROM pg_roles WHERE rolname='USR_NAME'

就命令行而言（感谢Erwin）：

psql postgres -tAc "SELECT 1 FROM pg_roles WHERE rolname='USR_NAME'"

如果找到则产生1，没有别的。

那是：

psql postgres -tAc "SELECT 1 FROM pg_roles WHERE rolname='USR_NAME'" | grep -q 1 || createuser ...

Answer 2

遵循与http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4492.pdf

相同的想法

psql -t -c '\du' | cut -d \| -f 1 | grep -qw <user_to_check>

你可以在这样的脚本中使用它：

if psql -t -c '\du' | cut -d \| -f 1 | grep -qw <user_to_check>; then
    # user exists
    # $? is 0
else
    # ruh-roh
    # $? is 1
fi

Answer 3

希望这可以帮助那些可能在 python 中执行此操作的人我在GitHubGist上创建了一个完整的工作脚本/解决方案 - 请参阅此代码段下方的URL。

# ref: https://stackoverflow.com/questions/8546759/how-to-check-if-a-postgres-user-exists
check_user_cmd = ("SELECT 1 FROM pg_roles WHERE rolname='%s'" % (deis_app_user))

# our create role/user command and vars
create_user_cmd = ("CREATE ROLE %s WITH LOGIN CREATEDB PASSWORD '%s'" % (deis_app_user, deis_app_passwd))

# ref: https://stackoverflow.com/questions/37488175/simplify-database-psycopg2-usage-by-creating-a-module
class RdsCreds():
    def __init__(self):
        self.conn = psycopg2.connect("dbname=%s user=%s host=%s password=%s" % (admin_db_name, admin_db_user, db_host, admin_db_pass))
        self.conn.set_isolation_level(0)
        self.cur = self.conn.cursor()

    def query(self, query):
        self.cur.execute(query)
        return self.cur.rowcount > 0

    def close(self):
        self.cur.close()
        self.conn.close()

db = RdsCreds()
user_exists = db.query(check_user_cmd)

# PostgreSQL currently has no 'create role if not exists'
# So, we only want to create the role/user if not exists 
if (user_exists) is True:
    print("%s user_exists: %s" % (deis_app_user, user_exists))
    print("Idempotent: No credential modifications required. Exiting...")
    db.close()
else:
    print("%s user_exists: %s" % (deis_app_user, user_exists))
    print("Creating %s user now" % (deis_app_user))
    db.query(create_user_cmd)
    user_exists = db.query(check_user_cmd)
    db.close()
    print("%s user_exists: %s" % (deis_app_user, user_exists))

Provides idempotent remote (RDS) PostgreSQL create role/user from python without CM modules, etc.

Answer 4

psql -qtA -c "\du USR_NAME" | cut -d "|" -f 1

[[ -n $(psql -qtA -c "\du ${1}" | cut -d "|" -f 1) ]] && echo "exists" || echo "does not exist"

如何检查postgres用户是否存在？

4 个答案: