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and needs to be cleaned up. My suggestion is that we not permit double-tagging. should not exist on questions. The architectures are totally different,

And, from the docs:

Greenplum Database is based on PostgreSQL open-source technology. It is essentially several PostgreSQL database instances acting together as one cohesive database management system (DBMS). It is based on PostgreSQL 8.2.15, and in most cases is very similar to PostgreSQL with regard to SQL support, features, configuration options, and end-user functionality. Database users interact with Greenplum Database as they would a regular PostgreSQL DBMS.

That means that essentially we're talking about a fork that occurred so long ago, that the version from which they forked on is no longer even supported upstream. It was released on 2009-12-14. That's over seven years ago. PostgreSQL only supports 9.2+. At the very least, this should not be tagged PostgreSQL. Ideally, I would like it to not be tagged either but because no one uses that tag, I agree the issue is somewhat moot.

This was inspired from this question which is tagged, and titled PostgreSQL however it has nothing to do with PostgreSQL. It's a Greenplum question, and it has that tag too.

The tag wiki for says the tag is supposed to be for all versions of Postgres. Simply put, Greenplum is a fork. It was never a version of PostgreSQL.

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    This looks similar to how MariaDB questions are sometimes (possibly often) also tagged mysql, MariaDB being a fork of MySQL. I'm aware that you mostly care about serious database products, just saying that there are other cases where questions about forked products are tagged in this manner, and that the community seemed to have no problem with that till now.
    – Andriy M
    Jan 23, 2017 at 6:30
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    I disagree with this policy. From my experience, the majority of the Greenplum questions that I have asked have had a PostgreSQL answer, often coming from someone who knows nothing about Greenplum. When it is a Greenplum specific problem, it is usually evident to me before I ask that there is something about the problem that is related to the distributed nature of the database, and so I forego the PostgreSQL tag. Sure, sometimes I might get that wrong, and I might waste the time of a PostgreSQL person. I guess it's a tradeoff, but this is my side of the story for your consideration.
    – PhilHibbs
    Mar 23, 2017 at 9:53

2 Answers 2

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I agree — a question shouldn't also be tagged .

From the Greenplum website:

Originally based on PostgreSQL

Apart from that there is hardly a mention, and I assume it will diverge more and more over time.

Also, from Wikipedia:

The primary competitors for Pivotal Greenplum Database, are the other MPP database systems provided by major industry vendors such as Teradata, Amazon Redshift, Azure Data Warehouse and IBM Netezza. Additional competition comes from other smaller competitors, column-oriented databases such as HP Vertica and data warehousing vendors with, non MPP architecture, such as Oracle Exadata, IBM DB2, and Hadoop distributions such as Cloudera and Hortonworks.

So it's not really likely that there'll be a huge crossover of Postgres experts interested in Greenplum questions.

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    When I've posted Greenplum questions in the past, I've been advised to tag them as Postgresql unless they are specifically related to the distributed nature of Greenplum. In the case of my most recent question, it turns out the answer is identical for both so both tags were appropriate.
    – PhilHibbs
    Mar 23, 2017 at 9:44
  • I would agree with this answer - if there was an exception. Something like: "greenplum questions shouldn't be tagged with postgres unless the question is about a SQL feature/query and is considered likely that the answer may be the same as for Postgres. We can then add the postgres-8.2 tag (or whichever version tag is more close to the related Greenplum version.)"
    – ypercubeᵀᴹ
    Mar 23, 2017 at 12:33
  • Although Greenplum was forked from Postgres 8.2, it is probable that feattures from later Postgre versions have been or will be merged into their versions.
    – ypercubeᵀᴹ
    Mar 23, 2017 at 12:34
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In my experience, is similar enough to that many questions will have answers that are equally applicable to both.

Yes, there is a risk that someone might ask a question whose answer hangs on a significant difference, and I have done that - posted a question that I did not know was Greenplum specific - and yes, that might have wasted the attention of someone who only knows PostgreSQL. Hopefully, though, such questions might be interesting to people who don't use Greenplum, I am always interested to learn things about database platforms that I am not currently using.

As long as people are encouraged to tag a question as PostgreSQL only if they believe that the question is equally relevant to either, then I believe that this policy should be advisory only. PostgreSQL tags certainly should be removed if it becomes apparent that the solution is only related either to Greenplum or the very old PostgreSQL base on which it is built.

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  • "In my experience", what is your experience? You've barely used this site and you pleading anecdotal evidence. PostgreSQL comes from Ingres. Ingres is the common parent of PostgreSQL, SQL Server, Sybase, and Greenplum. Perhaps your experience leads you to believe they're all similar enough? Looking at if the common-point of diversion is supported by the parent you fork off of sounds like a better way to determine this than anecdotal experiences.
    – Evan Carroll
    Mar 24, 2017 at 20:21
  • Problem isn't that the problem is specific to Grenplum or not, the problem is that by tagging things with PostgreSQL you solicit answers from PostgreSQL users. Those users should not be required to know what features were added in the past seven years. They have a different skill set. Their tool is substantially more advanced, and for most sophisticated problems their solutions will not work with Greenplum. You're talking about a world pre-window functions, json, fts, replication, lateral joins, event triggers, there is a ton of stuff we can't use to solve Greenplum problems.
    – Evan Carroll
    Mar 24, 2017 at 20:25
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    @EvanCarroll seriously? "What is your experience?"? He has been a user of the site for a year and a half. And greenplum has only 24 questions. He may read them all. Yesterday. (I shouldn't have to mention that he has asked or answered several of them).
    – ypercubeᵀᴹ
    Mar 24, 2017 at 21:47
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    My experience is thirty years of database software development, 20 in various flavours of SQL (Sybase, Oracle, DB2, MSSQL, MSAccess), 1.5 years experience in Greenplum, and 6 months in PostgreSQL 9.x.
    – PhilHibbs
    Mar 25, 2017 at 20:39
  • dba.stackexchange.com/a/168675/2639 for those reading along. =P
    – Evan Carroll
    Mar 30, 2017 at 18:17
  • dba.stackexchange.com/questions/175025/… ;)
    – dezso
    May 31, 2017 at 15:59

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