Exposed GEOSLineMergeDirected

[mdavis]

(Moved here from ​Dev list)

Expose the enhanced GEOS functionality ​GEOSLineMergeDirected

How should it be exposed in PostGIS? Nicest might be an optional "directed=false" flag on ST_LineMerge. But will that cause upgrade problems?

[mdavis]

Regina says:

It won’t cause any problems if you overload it rather than add a default arg.

The default arg is cleaner, since we won’t have an additional function to contend with.

The main danger with adding a default arg is anybody who is using ST_LineMerge in views will have some upgrade issues. Since adding a default arg requires dropping the old version.

Though Sandro made some adjustments to partly resolve that. ​https://trac.osgeo.org/postgis/ticket/5033

It renames the old function (assuming you put in the right availability comments) and then if there are views dependent on the old (because views references the oid of the function, and not the function name), then the upgrade will be in an incomplete upgrade state (will just have those dangling old names)

​https://trac.osgeo.org/postgis/changeset/3d947448b9c939b321bc22b85c719845722ecc3d/git

[komzpa]

Duplicates #4939

[mdavis]

This is the fix for #4939. It contains additional information useful for the implementation of the functionality.

[sergeish]

Tests using GEOS main branch (3.11.0dev) are failing on Github (PR: ​https://github.com/postgis/postgis/pull/688) when building PostGIS with error: implicit declaration of function 'GEOSLineMergeDirected' -- it seems that GEOS is a bit stale.

Is it updated automatically? Do I need to ask somebody to do it?

[robe]

Decided name is ST_LineMerge as Sergei has coded.

[sergei sh <sshoulbakov@…>]

In 9b0809b/git:

ST_LineMerge overload with "directed" argument.

Closes #5161