PostgreSQL: Column Disk usage

Question

I have a big table on my database, but it has a lot of empty fields on every column, and I´d like to know how much does every column use.

Is there any way to know how much disk space is each tables columns using?

pg_column_size()?

user330315
– user330315

2020-02-24 12:19:01 +00:00
Commented Feb 24, 2020 at 12:19 — user330315
– user330315, Commented Feb 24, 2020 at 12:19

Jim Jones · Accepted Answer · 2020-02-24 12:22:23Z

17

Try using pg_column_size(), it will return the column size in bytes:

SELECT sum(pg_column_size(column)) FROM yourtable

answered Feb 24, 2020 at 12:22

Jim Jones

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Laurenz Albe · Accepted Answer · 2020-02-24 15:35:24Z

3

As the documentation mentions, NULL values are indicated in the null bitmap of every tuple, which is always present if the table has nullable columns.

So a NULL value consumes no extra space on disk.

If you design tables with very many columns, rethink your design.

answered Feb 24, 2020 at 15:35

Laurenz Albe

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