Re: [GENERAL] Function to return per-column counts?

2017-09-28 Thread Melvin Davidson 
On Thu, Sep 28, 2017 at 3:31 PM, Seamus Abshere  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)
>
> --
> Seamus Abshere, SCEA
> https://www.faraday.io
> https://github.com/seamusabshere
> https://linkedin.com/in/seamusabshere
>
>
> --
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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

-- 
*Melvin Davidson*
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.

Re: [GENERAL] Function to return per-column counts?

2017-09-28 Thread Seamus Abshere 
> > > 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)

--
Seamus Abshere, SCEA
https://www.faraday.io
https://github.com/seamusabshere
https://linkedin.com/in/seamusabshere


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Re: [GENERAL] Function to return per-column counts?

2017-09-28 Thread John McKown 
On Thu, Sep 28, 2017 at 12:15 PM, Tomas Vondra  wrote:

>
>
> On 09/28/2017 04:34 PM, Seamus Abshere wrote:
> > hey,
> >
> > Does anybody have a function lying around (preferably pl/pgsql) that
> > takes a table name and returns coverage counts?
> >
>
> What is "coverage count"?
>

​I'm guessing it's what is described here:
https://www.red-gate.com/blog/sql-cover​

IIUC, this is "code coverage" for things kept in your RDMS system, such as
triggers, procedures, and other "code" items which are implicitly part of
your application code.



>
> cheers
>
> --
> Tomas Vondra  http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>


-- 
I just child proofed my house.
But the kids still manage to get in.


Maranatha! <><
John McKown

Re: [GENERAL] Function to return per-column counts?

2017-09-28 Thread Tomas Vondra 


On 09/28/2017 04:34 PM, Seamus Abshere wrote:
> hey,
> 
> Does anybody have a function lying around (preferably pl/pgsql) that
> takes a table name and returns coverage counts?
> 

What is "coverage count"?

cheers

-- 
Tomas Vondra  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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