Is there anything we can do to improve how questions are tagged and/or in GIS SE?

PostgreSQL is an object-relational database which supports spatial/geometry data, hence, there are questions which are on topic here for its own (aren't there? but not sure how big this niche is). PostGIS is a extension to PostgreSQL which adds support for geographic objects, and of course, is also on topic here.

So far we have:

  • 6154 question tagged [postgis];
  • 2598 questions tagged [postgresql];
  • 1806 questions tagged both.

Something, like this:

manually made venn diagram

Because, many questions are pertinent to both subjects it's been a while I have the impression there is (some) confusion when choosing which tags to use, i.e.:

  • using both tags when it is only about one product;
  • using one tag instead of the other (for example, using [postgresql] when it is (also) about [postgis]. (example).

Specially the second topic listed above, if it really happens it is bad, because it fragments content across the site (generate excessive duplicates).

Like many questions here about tags, we should consider not only how different/equal these products are in the 'real world', but how useful would be to GIS SE to relax (or make it stricter) the strategy to use such tags here.

So, is there anything you think is worth doing about these tags:

  • improving guidance on both tag excerpts (when to use one, when to use the other)?
  • making them synonyms?
  • creating a composite tag (like )?
  • doing nothing; other suggestions?

5 Answers 5


On one hand, as 'predicted' in question, some comments (here and here) and JGH's answer cited examples about subjects which would only be on-topic to PostgreSQL. I think it is a fair point.

On the other hand, it is still a bit of a mess how and tags are used in GIS SE, specially questions tagged only (because they are also about PostGIS; makes searching more difficult and lead to duplicates).

Therefore, my suggestion is (see the 'why' after it):

  1. Create a 'composite tag' .
  2. Write an excerpt to it explaining what it is and how to use it. Start suggestion:

Use this tag for GIS QUESTIONS about PostgreSQL AND/OR PostGIS. PostgreSQL is an open source object-relational database system. PostGIS is an extension for the PostgreSQL that adds support for geographic objects.

We can use the tag wiki to provide more guidance about when asking in Stack Overflow SE or Database Administrators SE.

  1. Make and synonyms of .
  2. After synonyms become stable, merge all of them (see: Can we merge all of our current tag synonyms?).


I think if it was not for PostGIS many users would still be using other databases systems such as MSSQL, MySQL, etc; even though PostgreSQL on its own is great. I think most people (specially in this community) agree one of its top differential is PostGIS.

Although, they are different products, in practice they are not (in the sense 'must be used together' for GIS purposes); so that is, many people still get confused what is one and what is the other.


I feel the S in GIS is often forgotten.

A question about connecting a piece of software (QGIS, ArcGIS, SHP2PGSQL, OGR2OGR etc) to a Postgres DB is on topic, though it has nothing to do with PostGIS.

Interoperability questions are also not related to PostGIS (ex: why a jsonb column doesn't show up in QGIS?)

There are other questions, on the verge of being off-topic, that still deserve the tag without the , such as questions on attribute field aggregation when using a spatial function.

At last, while the PostGIS product exists only under PostgresQL DB, they are still two separate products and we can think of all kind of compatibility issues that would make a question with both tags valid (ex: my query works with PG version X PostGIS version Y but fail after an update to PG Z.)

From these examples, I believe should exists on its own. I agree most questions should not have the tag too, though it should be an improved guidance, not a synonym.


In my opinion a question that is purely about PostgreSQL is off topic for GIS SE and should be migrated to DBA SE. Anything with a spatial content should be tagged anyway.

So I'd be happy to see converted into and then discourage general SQL/PostgreSQL questions by migrating them away.


postgis and postgresql are two different things clearly not synonymous to each other. Therefore,

making them synonyms?

seems to be wrong logically.

The third option:

creating a composite tag (like geotiff-tiff)?

seems to be rather cumbersome, like postgresql-postgis.

IMO, the other two options are better, either

doing nothing


improving guidance on both tag excerpts (when to use one, when to use the other)

, depending on what the actual harm is.


Another suggestion would be providing guidance in tag excerpts about how to use them. Bold parts are the potential new ones:


PostgreSQL is an open source object-relational database system. USE [postgis] tag if question is also about PostGIS.


PostGIS is an extension for the PostgreSQL object-relational database that adds support for geographic objects. DO NOT USE this tag for PostgreSQL questions unrelated to PostGIS.

We don't have bold formatting in excerpts, so the all caps would be to draw some attention to the 'how to use' parts.


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