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From Andreas Scherbaum <ascherb...@pivotal.io>
Subject Re: [gpdb-users] Re: Time consistency for DDL Available?
Date Wed, 05 Sep 2018 22:12:35 GMT
In recent PostgreSQL versions, WAL contains enough information (if
"wal_level" is set to "logical") to decode the raw data back into queries.
That feature is called "Logical Decoding".

https://www.postgresql.org/docs/current/static/logicaldecoding-explanation.html
https://wiki.postgresql.org/wiki/Logical_Decoding_Plugins

There are several plugins available which can decode the streamed data back
into different formats. One of them is "decoder_raw" which generates SQL
queries which can be consumed by another PostgreSQL database.


This allows for filter out DDL changes, and ignore DML.


Regards,
Andreas


On Wed, Sep 5, 2018 at 2:16 PM, <mpresser@pivotal.io> wrote:

> I don't believe there is any way to do this.  If you search for
> "postgresql track ddl changes", you'll likely conclude that there is no
> simple way to do this in postgresql.  There may be a way to do this but I
> think it will require some non trivial amount of hand coding.    If others
> know otherwise, please let us know.  MEP
>
> On Tuesday, September 4, 2018 at 5:22:02 PM UTC-4, Daniel Barale wrote:
>>
>> Hello all,
>>
>> Type 2 slowly changing dimensions allow the creation of time consistent
>> data views. When used properly, you can view the data “as it was” at a
>> point in time. So if a query myself today, using a 3 years ago time
>> criteria, I’d be able to see my address then, not where I live now, in case
>> I moved during that period.
>>
>> My question is, can we do the same with DDL metadata? I mean, is there a
>> system that allows having a table structure at a point in time, and having
>> the same table with a different structure at another point in time? Like
>> for instance, a table T had 3 integer columns in 1/1/2013 and in 12/12/2015
>> have the same 3 integer columns but also a date column added?
>>
>> Do u get my drift? Does Pivotal have a “tool” or feature to provide that?
>>
>> Ward regards
>>
>> Daniel Barale,
>>
>> Social Security Administration (USA)
>>
>> Daniel.e.barale@ssa.gov
>>
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-- 

*Andreas Scherbaum*

*Principal Software Engineer*

GoPivotal Deutschland GmbH


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