Re: Why is there no object create date is the catalogs? - Mailing list pgsql-general
I thank everyone for their feedback regarding the omission of object creation date from the catalog.
I do respect the various reasons for not including it, but I feel it is my duty to draw out this issue a bit longer.
I would like to counter the argument that a restore from a dump will override the create date.
That cannot happen.
If an object already exists, it cannot be created again. The worst case scenario is that an object must be dropped due to some terrible corruption or other disaster, in which case the creation date is not a major consideration.
Further to the point, why is it that both Oracle and SQL Server _do_ have the object create date in the catalogs?
http://stackoverflow.com/questions/4442323/how-to-find-out-when-a-particular-table-was-created-in-oracle
https://msdn.microsoft.com/en-us/library/ms190324.aspx
All I have heard so far is that the ONLY reason there is no object create date in pg_class is because there is no general agreement as to what create date means. Well I am giving it right now. When you execute the SQL statement of the form
CREATE TABLE ...
CREATE INDEX ...
CREATE SEQUENCE ...
CREATE MATERIALIZED VIEW ...
CREATE TYPE ...
CREATE FOREIGN TABLE ...
then that is when clock_timestamp() should be recorded as relcreatedate or relcreatetime.
Providing, of course, that the column is added to pg_class. :)I do respect the various reasons for not including it, but I feel it is my duty to draw out this issue a bit longer.
I would like to counter the argument that a restore from a dump will override the create date.
That cannot happen.
If an object already exists, it cannot be created again. The worst case scenario is that an object must be dropped due to some terrible corruption or other disaster, in which case the creation date is not a major consideration.
Further to the point, why is it that both Oracle and SQL Server _do_ have the object create date in the catalogs?
http://stackoverflow.com/questions/4442323/how-to-find-out-when-a-particular-table-was-created-in-oracle
https://msdn.microsoft.com/en-us/library/ms190324.aspx
All I have heard so far is that the ONLY reason there is no object create date in pg_class is because there is no general agreement as to what create date means. Well I am giving it right now. When you execute the SQL statement of the form
CREATE TABLE ...
CREATE INDEX ...
CREATE SEQUENCE ...
CREATE MATERIALIZED VIEW ...
CREATE TYPE ...
CREATE FOREIGN TABLE ...
then that is when clock_timestamp() should be recorded as relcreatedate or relcreatetime.
Is there some other overwhelming _technical_ reason that I am overlooking that prevents this from being done?
On Tue, May 12, 2015 at 8:08 PM, Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 05/12/2015 03:44 PM, Melvin Davidson wrote:Adrian,
You are over thinking this. An object is only "created" once! That is
what I meant by relcreatedate. If it is dropped, then it is deleted from
the catalogs. If it is modified, then it does NOT affect the creation
date. Everything else is superfluous.
See my original post and Tom Lanes response.
It is also not unusual for tables to have an end of cycle in certain
application, hence the need to be dropped after a certain time. EG.
Tables that track data only for a specific year.
Hence my link to the partitioning part of the manual.
Since PostgreSQL already tracks when tables are vacuum, auto vacuumed,
analyzed and auto analyzed ( pg_stat_all_tables ), I don't see why it is
such a big deal ( or so hard ) to track when an object is created. It
should be a very simple patch to the catalogs.
It is probably not a big deal to create a timestamp field and populate it. The issues arise when you start asking what it really means. The Postgres catalogs are not part of dump file, so the data in them will not transfer when you restore to another database. So on restore the create date will be the date the table is restored, not the date the table was originally created. For some people that is okay, for others not okay.
On Tue, May 12, 2015 at 6:00 PM, Adrian Klaver
<adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> wrote:
On 05/12/2015 12:51 PM, Melvin Davidson wrote:
Can anyone tell me why there is no "relcreated" column in
pg_class to
track the creation date of an object?
Meant to add to my previous post, back before I 'discovered' version
control I use to put the creation date in the table COMMENT:
http://www.postgresql.org/docs/9.4/interactive/sql-comment.html
It seems to me it would make sense to have one as it would
facilitate
auditing of when objects are created. In addition, it would also
facilitate the dropping of objects that have exceeded a certain age.
EG: SELECT 'DELETE TABLE ' || relname || ';'
FROM pg_class
WHERE relkind = 'r'
AND relcreated > current_timestamp - INTERVAL ' 1 year';
Adding that column should be relatively easy and would not break
backwards compatiblity with previous versions.
--
*Melvin Davidson*
--
Adrian Klaver
adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.
--
Adrian Klaver
adrian.klaver@aklaver.com
--
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.
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