在Postgres 9.1的表中有一个text
类型的列,我想知道仅该列对所需磁盘空间的影响。它不需要很精确,但我想大致了解该列是否占数据库消耗的磁盘空间的20%/30%/ ...。
我知道有pg_relation_size
,但它仅在表级别操作。
我有许多具有相同模式的数据库。我转储了一个较小的数据库,并使用grep和cut剪切了该列,然后比较了纯文本转储的大小。但这并不一定是现场数据库空间要求的良好指标,而且对于大型数据库来说也更难做到。
在Postgres 9.1的表中有一个text
类型的列,我想知道仅该列对所需磁盘空间的影响。它不需要很精确,但我想大致了解该列是否占数据库消耗的磁盘空间的20%/30%/ ...。
我知道有pg_relation_size
,但它仅在表级别操作。
我有许多具有相同模式的数据库。我转储了一个较小的数据库,并使用grep和cut剪切了该列,然后比较了纯文本转储的大小。但这并不一定是现场数据库空间要求的良好指标,而且对于大型数据库来说也更难做到。
select
sum(pg_column_size(the_text_column)) as total_size,
avg(pg_column_size(the_text_column)) as average_size,
sum(pg_column_size(the_text_column)) * 100.0 / pg_relation_size('t') as percentage
from t;
对已接受答案的稍微改进:美化输出大小,并使用pg_total_relation_size使结果更准确。
select
pg_size_pretty(sum(pg_column_size(column_name))) as total_size,
pg_size_pretty(avg(pg_column_size(column_name))) as average_size,
sum(pg_column_size(column_name)) * 100.0 / pg_total_relation_size('table_name') as percentage
from table_name;
BEGIN;
CREATE FUNCTION tc_column_size(table_name text, column_name text)
RETURNS BIGINT AS
$$
declare response BIGINT;
BEGIN
EXECUTE 'select sum(pg_column_size(t."' || column_name || '")) from ' || table_name || ' t ' into response;
return response;
END;
$$
LANGUAGE plpgsql;
SELECT
z.table_name,
z.column_name,
pg_size_pretty(z.size)
FROM (
SELECT
table_name,
column_name,
tc_column_size(table_name, column_name) size
FROM
information_schema.columns
WHERE
table_schema = 'public') AS z
WHERE
size IS NOT NULL
-- and z.table_name = 'my_table' -- <--- uncomment to filter a table
ORDER BY
z.size DESC;
ROLLBACK; -- <--- You may not want to keep that function
table_name
:EXECUTE 'select sum(pg_column_size(t."' || column_name || '")) from "' || table_name || '" t ' into response;
- Molomby