Automatically Drop Tables and Indexes Older than 90 Days [duplicate]

Answer 1

Are you sure you're approaching this the right way? You haven't explained what you're trying to do but it sounds like maybe it would be better solved by having a date column and a partition scheme.

Answer 2

You can get the creation time like this

(Assuming table name t_benutzer)

--select datname, datdba from pg_database;
--select relname, relfilenode from pg_class where relname ilike 't_benutzer';

    -- (select relfilenode::text from pg_class where relname ilike 't_benutzer')




SELECT 
    pg_ls_dir
    ,
    (
        SELECT creation
        FROM pg_stat_file('./base/'
            ||
            (
                    SELECT 
                        MAX(pg_ls_dir::int)::text 
                    FROM pg_ls_dir('./base') 
                    WHERE pg_ls_dir <> 'pgsql_tmp' 
                    AND  pg_ls_dir::int  <= (SELECT relfilenode FROM pg_class WHERE relname ILIKE 't_benutzer')
            )
            || '/' || pg_ls_dir
        )
    ) as createtime 
FROM pg_ls_dir(
    './base/' || 
    (
        SELECT 
            MAX(pg_ls_dir::int)::text 
        FROM pg_ls_dir('./base') 
        WHERE pg_ls_dir <> 'pgsql_tmp' 
        AND  pg_ls_dir::int  <= (SELECT relfilenode FROM pg_class WHERE relname ILIKE 't_benutzer') 
    ) 
) 

WHERE pg_ls_dir = (SELECT relfilenode::text FROM pg_class WHERE relname ILIKE 't_benutzer')

The secret is to use pg_stat_file on the respective table file.

-- http://www.greenplumdba.com/greenplum-dba-faq/howtofindtablecreationdateingreenplum


select 
    pg_ls_dir
    , 
    (
        select 
            --size 
            --access
            --modification 
            --change
            creation 
            --isdir
        from pg_stat_file(pg_ls_dir)
    ) as createtime 
from pg_ls_dir('.'); 

As per comment in this post PostgreSQL: Table creation time this isn't 100% reliable, because the table may have been internally dropped and recreated due to operations on the table, such as CLUSTER.

Also the pattern

/main/base/<database id>/<table filenode id> 

seems to be wrong, as on my machine, all tables from different databases have the same database id, and it seems like the folder has been replaced with some arbitrary inode number, so you need to find the folder whose number is closest to your table's inode id (max foldername where folderid <= table_inode_id and foldername is numeric)

Simplified version goes like this:

SELECT creation 
FROM pg_stat_file(
    './base/'
    ||
    (
        SELECT 
        MAX(pg_ls_dir::int)::text 
        FROM pg_ls_dir('./base') 
        WHERE pg_ls_dir <> 'pgsql_tmp' 
        AND  pg_ls_dir::int  <= (SELECT relfilenode FROM pg_class WHERE relname ILIKE 't_benutzer')
    )
    || '/' || (SELECT relfilenode::text FROM pg_class WHERE relname ILIKE 't_benutzer')
)

Then you can use information_schema and cte to make the query simple, or create your own view:

;WITH CTE AS
(
    SELECT 
        table_name 

        ,
        (
            SELECT 
                MAX(pg_ls_dir::int)::text 
            FROM pg_ls_dir('./base') 
            WHERE pg_ls_dir <> 'pgsql_tmp' 
            AND  pg_ls_dir::int  <= (SELECT relfilenode FROM pg_class WHERE relname ILIKE table_name)
        ) as folder 


        ,(SELECT relfilenode FROM pg_class WHERE relname ILIKE table_name) filenode

    FROM information_schema.tables
    WHERE table_type = 'BASE TABLE'
    AND table_schema = 'public'
)

SELECT 
    table_name 
    ,(
        SELECT creation 
        FROM pg_stat_file(
            './base/' || folder || '/' || filenode 
        )
    ) as creation_time
FROM CTE 

(all tables created with nhibernate schema create, so the more or less same time on all tables on the screenshot is correct).

For risk and side effects, use your brain and/or ask your doctor or pharmacist ;)