Geospatial types support (initial version - POINTS only)

[snork-alt]

We need to support geospatial types and functions in Dozer. The work will consist of the following:

• Extend dozer-types to support geospatial types
• Allow creation and casting of geospatial types
• Include support in connectors for geospatial-types conversions
• Include support for geospatial types in the cache writer
• Implement various geospatial functions
• Update all relevant documentation

For the implementation, we will use the Rust Geo library (https://docs.rs/geo/latest/geo/)
The initial version will have limited support for geo data types. We will extend it later after we will introduce the ARRAY type

Types support

We shall extend the dozer-types with the following types mapped 1 to 1 with the Rust Geo types:

• Coord
• Point
• Polygon

Creation

The creation of the above types should be supported through SQL functions. In particular:

• COORD(FLOAT, FLOAT)
• POINT(COORD)
• POLYGON(COORDS, ...)

Functions

DISTANCE(POINT, POINT, [GEODESIC | HAVERSINE | VINCENTY]) - defaults to GEODESIC
CONTAINS(POLYGON, POINT | POLYGON)

[snork-alt]

@mediuminvader @karolisg

[karolisg]

@snork-alt What is the difference between Point and Coord types? Do we really need two different types, which represent the same data?

[mediuminvader]

it's based on mapping the rust geo implementation, quoting the crate docs:

[edit: Coord is] A lightweight struct used to store coordinates on the 2-dimensional Cartesian plane.
Unlike Point (which in the future may contain additional information such as an envelope, a precision model, and spatial reference system information), a Coord only contains ordinate values and accessor methods.

[karolisg]

Got it. Now it is clear for me.

[chubei]

I don't think we need the Coord type. Because coord is the underlying representation of Point, Polygon, etc. It's not a geo type.

[mediuminvader]

Good Point 😆

[karolisg]

In that case, do we need COORD function in SQL? Can we use POINT(FLOAT, FLOAT)?

[mediuminvader]

Right, let’s go with POINT(FLOAT,FLOAT)

[karolisg]

@snork-alt @mediuminvader

What should be the result of function POINT(FLOAT, FLOAT) and DISTANCE(POINT, POINT) when one or both arguments are null? I checked several implementations and it looks like the NULL result is it most common result.

Also, do we need to implement support for geo types from snowflake in the initial version?

[v3g42]

Would be nice to consider indexing these types on cache as well. Though it is not a high priority item right now.