The query also can change the order of the columns using FIRST | AFTER clause, see ADD COLUMN description, but column type is mandatory in this case. Example: CREATE TABLE users ( c1 Int16, c2 String) ENGINE = MergeTreeORDER BY c1;DESCRIBE users;┌─name─┬─type───┬│ c1 │ Int...
-- By default, for backward compatibility a settings profile constraint for a specific setting inherit every not set field from previous profile. You can change this behaviour by setting this to true. If it's set to true then if settings profile has a constraint for a specific setting, then...
--optimize_if_transform_strings_to_enum arg Replaces string-type arguments in If and Transform to enum. Disabled by default cause it could make inconsistent change in distributed query that would lead to its fail. --optimize_monotonous_functions_in_order_by arg Replace monotonous function with ...
it’s applied only to the batch of freshly inserted data. Any changes to existing data of source table (like update, >delete, drop partition, etc.) does not change the materialized view.
SQL 语句查询 table_1 来完成，但是我们不难发现 dt 是一致的，区别在于 type 和 status 两个条件。
在DataType的实现类中，聚合了相应数据类型的Column对象和Field对象。例如，DataTypeString会引用字符串...
┌─Column Name───┬─Column Type─┬─compressed─┬─uncompressed─┬─Compression Ratio─┬─compression_codec─┐ │ changeable │ UInt8 │ 188.32 KiB │ 41.27 MiB │ 224.41 │ │ │ averageSignal │ UInt8 │ 188.32 KiB │ 41.27 MiB │ 224.41 │ │ ...
ClickHouse中分为DistributeTable、LocalTable、Partition、Shard、Part、Column几个部分,差不多能和Doris对应起来,区别就是CH中每个Column都对应一组数据文件和索引文件,好处就是命中系统Cache性能更高,不好的地方就是IO较高且文件数量较多,另外CH有Count索引,所以Count时命中索引会比较快。
ProxySQL-ClickHouse> ALTER TABLE newTable2 ADD COLUMN col2 String; Query OK, 0 rows affected (0.16 sec) ProxySQL-ClickHouse> SHOW CREATE TABLE newTable2\G *** 1. row *** statement: CREATE TABLE default.newTable2 ( id UInt64, name String, Event...
* Allows to insert, remove columns in arbitrary position, to change order of columns. */ Processors实际执行query pipeline的组件是庞大而丰富的processors,它们是底层执行的基础构件。^IProcessor$ └── IProcessor ├── AggregatingInOrderTransform ├── AggregatingTransform ├── ConcatProcessor ├─...