Question

我将加载表从Postgres迁移到Clickhouse，以便进一步创建pg的FOREIGN TABLE和MATERIALIZED VIEW。但是，当尝试按created_at分组时，我得到了奇怪的结果，就像有些时候我根本没有负载：

# Clickhouse
CREATE TABLE loads(
    country_id UInt16,
    created_at Date
) ENGINE=MergeTree PARTITION BY toYYYYMM(created_at) ORDER BY (created_at);

# Pg
CREATE EXTENSION clickhousedb_fdw;
CREATE SERVER clickhouse_svr FOREIGN DATA WRAPPER clickhousedb_fdw OPTIONS(dbname 'db', driver '/usr/local/lib/odbc/libclickhouseodbc.so', host '127.0.0.1');
CREATE USER MAPPING FOR CURRENT_USER SERVER clickhouse_svr options(user 'default', password 'pwd');

CREATE FOREIGN TABLE dwh_loads(
    country_id int,
    created_at date
) SERVER clickhouse_svr;

因此，在Clickhouse上分组归还可以，但是pg外部表的结果却很奇怪，几天过去了：

# Clickhouse
SELECT 
    count(*), 
    created_at
FROM dwh_loads
WHERE created_at > '2019-08-10'
GROUP BY created_at
ORDER BY created_at ASC

┌─count()─┬──────created_at─┐
│ 1987751 │      2019-08-11 │
│ 2225018 │      2019-08-12 │
│ 4098923 │      2019-08-13 │
│ 7453111 │      2019-08-14 │
│ 6787449 │      2019-08-15 │
│ 6396884 │      2019-08-16 │
│ 5642157 │      2019-08-17 │
│ 5485166 │      2019-08-18 │
│ 4949855 │      2019-08-19 │
│ 4968256 │      2019-08-20 │
│ 4583210 │      2019-08-21 │
│ 4781908 │      2019-08-22 │
│ 4449216 │      2019-08-23 │
│ 4911274 │      2019-08-24 │
│  205194 │      2019-08-25 │
└─────────┴─────────────────┘

# Pg
select count(*), created_at 
from dwh_loads where created_at > '2019-08-10' 
group by created_at 
order by created_at;
  count  | created_at_date 
---------+-----------------
 1752400 | 2019-08-11
 3604480 | 2019-08-16
 1637314 | 2019-08-18
     823 | 2019-08-24

但是，如果我查询确切的日期-pg返回正确的结果： where created_at_date = '2019-08-20'返回4968256。

Clickhouse分组陈述期间的奇怪行为

0 个答案: