timescaledb_information.hypertable

获得时序元数据表的详细信息。

字段及其含义

示例：

查询所有时序元数据表信息：

SELECT * FROM timescaledb_information.hypertable;
 table_schema | table_name | table_owner | num_dimensions | num_chunks | table_size | index_size | toast_size | total_size
--------------+------------+-------------+----------------+------------+------------+------------+------------+------------
 public       | metrics    | postgres    |              1 |          5 | 99 MB      | 96 MB      |            | 195 MB
 public       | devices    | postgres    |              1 |          1 | 8192 bytes | 16 kB      |            | 24 kB
(2 rows)

检查表是否是时序元数据表

SELECT * FROM timescaledb_information.hypertable
WHERE table_schema='public' AND table_name='metrics';
 table_schema | table_name | table_owner | num_dimensions | num_chunks | table_size | index_size | toast_size | total_size
--------------+------------+-------------+----------------+------------+------------+------------+------------+------------
 public       | metrics    | postgres    |              1 |          5 | 99 MB      | 96 MB      |            | 195 MB
(1 row)

chunk_relation_size()

获得时序元数据表的数据块关系。返回值是一张表。

必选参数

返回值

示例：

SELECT * FROM chunk_relation_size('conditions');

或者选取部分列进行输出

SELECT chunk_table, table_bytes, index_bytes, total_bytes
FROM chunk_relation_size('conditions');

期望输出:

chunk_table                 | table_bytes | index_bytes | total_bytes
---------------------------------------------+-------------+-------------+-------------
 "_timescaledb_internal"."_hyper_1_1_chunk"  |    29220864 |    37773312 |    67002368
 "_timescaledb_internal"."_hyper_1_2_chunk"  |    59252736 |    81297408 |   140558336
 ...

chunk_relation_size_pretty()

与chunk_relation_size()功能相同，显示格式不同。

必选参数

Returns

示例：

SELECT * FROM chunk_relation_size_pretty('conditions');

或者选取部分列进行输出

SELECT chunk_table, table_size, index_size, total_size
FROM chunk_relation_size_pretty('conditions');

期望输出

chunk_table                  | table_size | index_size | total_size
---------------------------------------------+------------+------------+------------
 "_timescaledb_internal"."_hyper_1_1_chunk"  | 28 MB      | 36 MB      | 64 MB
 "_timescaledb_internal"."_hyper_1_2_chunk"  | 57 MB      | 78 MB      | 134 MB
 ...

hypertable_approximate_row_count()

计算时序元数据表行数近似值

可选参数

示例：

计算conditions时序元数据表行数近似值

SELECT * FROM hypertable_approximate_row_count('conditions');

计算所有时序元数据表行数近似值

SELECT * FROM hypertable_approximate_row_count();

期望输出

schema_name | table_name | row_estimate
-------------+------------+--------------
  public     | conditions |      240000

hypertable_relation_size()

获得时序元数据表的关系表。

必选参数

返回值

示例：

SELECT * FROM hypertable_relation_size('conditions');

或者选取部分列进行输出

SELECT table_bytes, index_bytes, toast_bytes, total_bytes
FROM hypertable_relation_size('conditions');

期望输出

table_bytes | index_bytes | toast_bytes | total_bytes
---------------+----------------+----------------+-------------
  1227661312 |  1685979136 |      180224 |  2913820672

hypertable_relation_size_pretty()

与hypertable_relation_size()相同，显示格式有区别。

必选参数

返回值

示例：

SELECT * FROM hypertable_relation_size_pretty('conditions');

或者选取部分列进行输出

SELECT table_size, index_size, toast_size, total_size
FROM hypertable_relation_size_pretty('conditions');

期望输出

table_size | index_size | toast_size | total_size
------------+------------+------------+------------
 1171 MB    | 1608 MB    | 176 kB     | 2779 MB

indexes_relation_size()

获得时序元数据表索引大小。

必选参数

Returns

示例：

SELECT * FROM indexes_relation_size('conditions');

期望输出

index_name              | total_bytes
--------------------------------------+-------------
 public.conditions_device_id_time_idx |  1198620672
 public.conditions_time_idx           |   487358464

indexes_relation_size_pretty()

与indexes_relation_size()相同，显示格式有区别。

必选参数

返回值

示例：

SELECT * FROM indexes_relation_size_pretty('conditions');

期望输出

index_name_              | total_size
--------------------------------------+------------
 public.conditions_device_id_time_idx | 1143 MB
 public.conditions_time_idx           | 465 MB