如何使用Sqlalchemy创建序列并将特定序列添加到表中？

Question

rollback.py :

def write_to_db(dataset_id):
    try:
        initialize_datamodels()
        EpdUmpPushRollback = datamodels.relational_tables.EpdUmpPushRollback
        with session_scope() as session:
            epdumppushrollback_obj = EpdUmpPushRollback()
            epdumppushrollback_obj.dataset_id = dataset_id
            epdumppushrollback_obj.record_id = ''
            epdumppushrollback_obj.operator_name = 'vis'
            epdumppushrollback_obj.activation_flag = 'active'
            epdumppushrollback_obj.record_creation_time = now()
            epdumppushrollback_obj.start_time = now()
            session.add(epdumppushrollback_obj)
            session.flush()

    except Exception as e:
        #err = "Error in updating the table epd_ump_push_rollback "
        #_log.exception(err)
        _log.exception("Error in updating the table {}".format(e))

table.py :

"""epd_ump_push_rollback_table

Revision ID: 4e4d99a8e544
Revises: c010f4d4b319
Create Date: 2018-12-19 18:04:30.271380

"""
from alembic import op
from sqlalchemy import Column, String, INTEGER, VARCHAR, NVARCHAR, TIMESTAMP, \
    Enum, ForeignKey, Sequence, MetaData

# revision identifiers, used by Alembic.
revision = '4e4d99a8e544'
down_revision = '2396e1b7de5c'
branch_labels = None
depends_on = None

meta = MetaData()
seq_obj = Sequence('record_id_seq', metadata=meta)


def upgrade():
    activation_flag_state = Enum('active', 'inactive', name="activation_flag_state")

    op.create_table('epd_ump_push_rollback',
                    Column('dataset_id', String, ForeignKey('epd_ip_dataset.dataset_id'),
                           primary_key=True),
                    Column('record_id', INTEGER, seq_obj, server_default=seq_obj.next_value(),
                           primary_key=True),
                    Column('operator_name', String, nullable=False),
                    Column('activation_flag', activation_flag_state, nullable=False),
                    Column('record_creation_time', TIMESTAMP),
                    Column('start_time', TIMESTAMP),
                    Column('end_time', TIMESTAMP))


def downgrade():
    op.drop_table('epd_ump_push_rollback')
    op.execute('DROP type activation_flag_state')

说明：

在rollback.py文件中，我正在写入db。我正在使用with session_scope() as session:设置与db(postgresql)的会话。我正在创建表EpdUmpPushRollback的对象并适当地设置这些值。列record_id应该被生成为序列，我在table.py中定义了这个序列，我正在使用alembic将我的模式升级到新的模式，这个模式将包含表EpdUmpPushRollback。你知道吗

我现在有两个问题。你知道吗

1. 对于定义了sequence的列，是强制使用pdumppushrollback_obj.record_id = ''添加还是自动添加？你知道吗
2. 序列的名称应该是什么，每当我试图在表中添加任何条目时，它都会抛出这个错误。你知道吗

Error: sqlalchemy.exc.ProgrammingError: (psycopg2.ProgrammingError) "record_id_seq" is not a sequence [SQL: 'INSERT INTO epd_ump_push_rollback (dataset_id, operator_name, activation_flag, record_creation_time, start_time, end_time) VALUES (%(dataset_id)s, %(operator_name)s, %(activation_flag)s, now(), now(), %(end_time)s) RETURNING epd_ump_push_rollback.record_id'] [parameters: {'dataset_id': '20181221_1200_mno', 'operator_name': 'vis', 'activation_flag': 'active', 'end_time': None}]

Answer 1

我曾经遇到过这个问题，为了解决这个问题，我创建了序列，所以您可以尝试以下postgres语句：

CREATE SEQUENCE record_id_seq
   START WITH 1
   INCREMENT BY 1
   NO MINVALUE
   NO MAXVALUE
   CACHE 1;