使用 MergeTree 引擎 Clickhouse 创建分区键时出错答案

【问题标题】：Error creating partition key using MergeTree engine, Clickhouse使用 MergeTree 引擎 Clickhouse 创建分区键时出错
【发布时间】：2020-11-09 19:35:46
【问题描述】：

我一直在尝试使用 infi.clickhouse_orm 创建模型，但分区键出现问题

我的模特：

from infi.clickhouse_orm import Model,  UInt16Field, Float32Field, StringField, MergeTree,DateField

class OHLC(Model):

__tablename__ = 'ohlc'

id = UInt16Field()
min = Float32Field()
max = Float32Field()


start_date = DateField()
interval = StringField()

engine = MergeTree(partition_key=['id'])

我得到错误：

DB::Exception：语法错误：.. 设置 index_granularity=8192。预期之一：箭头，令牌，非空括号列表表达式

创建我的数据库

""" SqlAlchemy ClickHouse database session maker """

db = Database('test', db_url=os.environ['TEST_CONNECTION'],
              username=os.environ['CLICKHOUSE_USER'], password=os.environ['CLICKHOUSE_PASSWORD'])
db.create_database()
db.create_table(OHLC)

【问题讨论】：

标签： python-3.x docker-compose sqlalchemy clickhouse

【解决方案1】：

MergeTree-engine 需要在 order_by-参数中传递的表声明中的主键：

..
engine = MergeTree(partition_key=['id'], order_by=['id'])
..

from infi.clickhouse_orm.engines import MergeTree
from infi.clickhouse_orm.fields import UInt16Field, Float32Field, StringField, DateField
from infi.clickhouse_orm.models import Model
from sqlalchemy import create_engine


class OHLC(Model):
    __tablename__ = 'ohlc'
    id = UInt16Field()
    min = Float32Field()
    max = Float32Field()
    start_date = DateField()
    interval = StringField()
    engine = MergeTree(partition_key=['id'], order_by=['id'])


engine = create_engine('clickhouse://default:@localhost/test_001')

with engine.connect() as conn:
    conn.connection.create_database()
    conn.connection.create_table(OHLC)

requirements.txt

sqlalchemy==1.3.18
sqlalchemy-clickhouse==0.1.5.post0
infi.clickhouse_orm==1.3.0

使用 id 作为partition key 看起来很可疑，考虑将其定义为 toYYYYMM(start_date) 或类似的东西：

class OHLC(Model):
    __tablename__ = 'ohlc'
    id = UInt16Field()
    min = Float32Field()
    max = Float32Field()
    start_date = DateField()
    interval = StringField()
    engine = MergeTree(partition_key=['toYYYYMM(start_date)'], order_by=['id'])

【讨论】：