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TimescaleDB 时序数据库

时序数据库 https://github.com/timescale/timescaledb

数据库配置 https://github.com/timescale/timescaledb-tune

copy并行导入数据 https://github.com/timescale/timescaledb-parallel-copy

常用方法

创建拓展

CREATE EXTENSION timescaledb;

创建一个普通的表

CREATE TABLE conditions (
  time        TIMESTAMPTZ       NOT NULL,
  location    TEXT              NOT NULL,
  temperature DOUBLE PRECISION  NULL,
  humidity    DOUBLE PRECISION  NULL
);

转换成时序数据库表

SELECT create_hypertable('conditions', 'time');
  • conditions 表名
  • time 时序字段

修改时序间隔 对新表生效

SELECT set_chunk_time_interval('conditions', INTERVAL '24 hours');

查看分区

SELECT show_chunks('conditions');

SELECT show_chunks('conditions', older_than => INTERVAL '3 months')

SELECT show_chunks('conditions', older_than => DATE '2017-01-01');

SELECT show_chunks(newer_than => INTERVAL '3 months');

SELECT show_chunks(older_than => INTERVAL '3 months', newer_than => INTERVAL '4 months');

查看数据大小

SELECT * FROM timescaledb_information.hypertable;

自动删除

添加规则
SELECT add_drop_chunks_policy('conditions', INTERVAL '6 months');
删除规则
SELECT remove_drop_chunks_policy('conditions');

注意事项

When creating hypertables, one constraing that TimescaleDB imposes is that the partitioning column (in your case 'date_time') must be included in any unique indexes (and Primary Keys) for that table.

https://stackoverflow.com/questions/61205063/error-cannot-create-a-unique-index-without-the-column-date-time-used-in-part

时序数据特征

  • have a timestamp
  • append only ,less update or delete
  • recent hot

限制

除分区列外不可以在其他列中有唯一约束

原数据库中的唯一约束为全局表内唯一约束，在分区表（chunks）中不能够保证全局唯一

When converting a normal SQL table to a hypertable, pay attention to how you handle constraints.
A hypertable can contain foreign keys to normal SQL table columns, but the reverse is not allowed. UNIQUE and PRIMARY constraints must include the partitioning key.

最佳实践

chunk 时间范围

与数据量有关，一个chunk容量约1/4 内存大小

SELECT * FROM create_hypertable('conditions', 'time',
       chunk_time_interval => INTERVAL '1 day');
组合索引

1 等值查询 （e,time）e 为等值查询列 time 为分区时间列
2 范围查询 (time,c) c 为连续值列

排序
压缩

设置历史数据压缩策略，压缩后变成列存，且为只读

``` alter table conditions set( timescaledb.compress);

timescaledb.compress_segmentby timescaledb.compress_orderby 设置压缩策略 SELECT add_compress_chunks_policy('conditions', INTERVAL '60d'); 删除压缩策略 remove_compress_chunks_policy() 手动压缩 SELECT compress_chunk('_timescaledb_internal._hyper_1_2_chunk'); 解压缩 SELECT compress_chunk('_timescaledb_internal._hyper_1_2_chunk'); 查看压缩情况 SELECT * FROM timescaledb_information.compressed_chunk_stats; ```

手动批量压缩

SELECT compress_chunk(i) from show_chunks('conditions', newer_than, older_than) i;

保留策略

设置保留数据策略

SELECT add_drop_chunks_policy('conditions', INTERVAL '24 hours');
连续分析窗口

物化视图自动持续更新

更多信息查看

比如压缩策略，保留策略，持续集成策略等

\dv timescaledb_information.*
                            List of relations
         Schema          |            Name             | Type |  Owner   
-------------------------+-----------------------------+------+----------
 timescaledb_information | compressed_chunk_stats      | view | postgres
 timescaledb_information | compressed_hypertable_stats | view | postgres
 timescaledb_information | continuous_aggregate_stats  | view | postgres
 timescaledb_information | continuous_aggregates       | view | postgres
 timescaledb_information | drop_chunks_policies        | view | postgres
 timescaledb_information | hypertable                  | view | postgres
 timescaledb_information | license                     | view | postgres
 timescaledb_information | policy_stats                | view | postgres
 timescaledb_information | reorder_policies            | view | postgres