clickhouse（四、運維查看數據庫及表容量）

mysql數據庫有information_schema.tables系統表記錄表相關元數據，clickhouse對應的有system.parts表。下面是查看clickhouse數據庫和表大小、行數及壓縮率等方法。

-- 查看數據庫容量，以測試數據爲參考
select
    sum(rows) as "總行數",
    formatReadableSize(sum(data_uncompressed_bytes)) as "原始大小",
    formatReadableSize(sum(data_compressed_bytes)) as "壓縮大小",
    round(sum(data_compressed_bytes) / sum(data_uncompressed_bytes) * 100, 0) "壓縮率"
from system.parts;

┌──────總行數─┬─原始大小──┬─壓縮大小─┬─壓縮率─┐
│ 169851144587 │ 30.76 TiB │ 4.51 TiB │     15 │
└─────────────┴───────────┴──────────┴────────┘

1 rows in set. Elapsed: 1.462 sec. Processed 90.35 thousand rows, 42.81 MB (63.76 thousand rows/s., 30.60 MB/s.) 


-- 查詢test表，2019年10月份的數據容量
select
    table as "表名",
    sum(rows) as "總行數",
    formatReadableSize(sum(data_uncompressed_bytes)) as "原始大小",
    formatReadableSize(sum(data_compressed_bytes)) as "壓縮大小",
    round(sum(data_compressed_bytes) / sum(data_uncompressed_bytes) * 100, 0) "壓縮率"
from system.parts
	-- 根據實際情況加查詢條件
    where table in('test')
        and partition like '2019-10-%'
    group by table;		

┌─────總行數─┬─原始大小───┬─壓縮大小──┬─壓縮率─┐
│ 3015199559 │ 727.83 GiB │ 60.34 GiB │      8 │
└────────────┴────────────┴───────────┴────────┘

1 rows in set. Elapsed: 0.227 sec. Processed 3.52 thousand rows, 1.70 MB (15.48 thousand rows/s., 7.50 MB/s.) 

下一節 我們來看下如何查看後臺進程並殺死。