Обсуждение: [GENERAL] Function to return per-column counts?
On Thu, Sep 28, 2017 at 3:31 PM, Seamus Abshere <seamus@abshere.net> wrote:
> > > Does anybody have a function lying around (preferably pl/pgsql) that
> > > takes a table name and returns coverage counts?
> >
> > What is "coverage count"?
Ah, I should have explained better. I meant how much of a column is
null.
Basically you have to
0. count how many total records in a table
1. discover the column names in a table
2. for each column name, count how many nulls and subtract from total
count
If nobody has one written, I'll write one and blog it.
Thanks!
Seamus
PS. In a similar vein, we published
http://blog.faraday.io/how-to-do-histograms-in-postgresql/ which gives
plpsql so you can do:
SELECT * FROM histogram($table_name_or_subquery, $column_name)
--
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I can't really do the full query for you, but the following should be able to give you a head start:
SELECT c.relname AS table,
a.attname AS column,
a.attnum AS colnum,
s.stanullfrac as pct_null,
s.stadistinct
FROM pg_class c
JOIN pg_attribute a ON a.attrelid = c.oid
JOIN pg_statistic s ON (s.starelid = c.oid AND s.staattnum = a.attnum)
WHERE c.relname = 'your_table_name'
AND a.attnum > 0
ORDER BY 3
a.attname AS column,
a.attnum AS colnum,
s.stanullfrac as pct_null,
s.stadistinct
FROM pg_class c
JOIN pg_attribute a ON a.attrelid = c.oid
JOIN pg_statistic s ON (s.starelid = c.oid AND s.staattnum = a.attnum)
WHERE c.relname = 'your_table_name'
AND a.attnum > 0
ORDER BY 3
--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.