[Potential bug?] Update spatial_relationships_exercises.rst

[ThomasPrioul]

Using a subquery instead of a string MULTILINESTRING or LINESTRING gives different and more accurate results. The exercise asks for the following question : What streets does Atlantic Commons join with?

There seems to be a difference between raw geometry format and back/forth serialization! Maybe it is related to the SRID aspects ?

Using multilinestring or subquery :

Using suggested parsed linestring :

Also, for completion purpose, shouldn't the question be answered excluding the street itself (atlantic commons) ?

[coderabbitai[bot]]

📝 Walkthrough

Walkthrough

The changes update the SQL query in the spatial_relationships_exercises.rst document. The hardcoded LINESTRING geometry for 'Atlantic Commons' has been replaced with a subquery that dynamically retrieves the geometry from the nyc_streets table. Additionally, the explanatory note regarding the use of LINESTRING over MULTILINESTRING, and the rounding effects on the ST_Touches() predicate, remains intact.

Changes

File	Change Summary
postgis-intro/.../spatial_relationships_exercises.rst	Updated SQL query: replaced hardcoded LINESTRING geometry with a subquery selecting 'Atlantic Commons' geometry; retained note explaining the geometry type and rounding.

Sequence Diagram(s)

sequenceDiagram
    participant U as User
    participant Q as Query Engine
    participant DB as nyc_streets Table

    U->>Q: Execute spatial_relationship query
    Q->>DB: Run subquery to fetch 'Atlantic Commons' geometry
    DB-->>Q: Return geometry data
    Q->>Q: Substitute geometry in the main query
    Q-->>U: Return query results based on dynamic geometry

Poem

I’m a rabbit dancing through lines of code,
Hopping over hardcoded paths now old.
Dynamic queries sing a brand new tune,
As geometry leaps beneath the moon.
A happy hop for every refined node!
🐇🐾

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[robe2]

Using a subquery instead of a string MULTILINESTRING or LINESTRING gives different and more accurate results. The exercise asks for the following question : What streets does Atlantic Commons join with?

There seems to be a difference between raw geometry format and back/forth serialization! Maybe it is related to the SRID aspects ?

I think it's different because the ST_AsText is a rounded geometry, not the actual geometry, so it's no surprise they are different. SRID wouldn't have a play here since everything is in the same SRID and no transform going on here as I recall.

Also, for completion purpose, shouldn't the question be answered excluding the street itself (atlantic commons) ? Yes I would say so, but it would complicate the query a tiny bit so deviates a bit from the intent of the exercise with introducing too much reality.

As to replacing the ST_AsText with a sub query, I do kinda like that more than including the ST_AsText of prior exercise.

@pramsey @dr-jts what are you feelings about the suggested change?

[dr-jts]

I agree with both suggested changes (i.e. use actual data record in filter, and exclude that record from the result), for the following reasons:

• It produces a correct result
• It corresponds more closely to a real world query (which are much more likely to refer to other data items than contain explicit data)

The previous example query (What neighborhood and borough is Atlantic Commons in?) could also be improved in the same way.