[jravani]

The link step kept one OSM way per 3D building (DISTINCT ON (b.object_id), UNIQUE (object_id, country_code)). Where OSM maps one building as several ways, the others got no building_link row although each cleared the 0.5 threshold, so a caller asking for them found no 3D data.

Closes #203

Change

• sql/scripts/link/pylovo/01_build_pylovo_link.sql links every way with confidence ≥ 0.5, from res and oth. Ranking per 3D building: res before oth, confidence to two decimals (exact copies differ only by reprojection noise), larger overlap, osm_id. Rank 1 keeps match_type 1; every further way gets the new match_type 4 with the same object_id.
• building_link is unique per (object_id, osm_id, country_code) and allows match_type 4. internal/process/link_table.go brings a table from an earlier release to that shape once per link run, under an advisory lock.
• GetGridBatches excludes linked buildings with NOT EXISTS instead of a join, since a building can now have several rows.
• GET /api/v1/buildings?osm_ids= returns each 3D building once, however many of its ways are asked for. osm_id stays the best way; the new osm_ids lists every linked way, best first, then by confidence. It is always present and [] in bbox mode.
• Docs: docs/code/pylovo-link/index.md, the OpenAPI Building schema and getBuildings description, CHANGELOG.md.

Example, DEBY_LOD2_7595822: asking for 1265475272 returns that building once, with osm_id 223728275 and osm_ids [223728275, 1265475272, 1414567368, 1414567366, 1414567367].

Effect on existing data

Re-linking a copy of the German demo database (-link-pylovo -relink) adds 63 further-way rows on 49 buildings. No building's best way changes. 1,173 distinct OSM ways have 3D data afterwards, against 1,120 before. Existing databases need -link-pylovo -relink to fill in further ways for buildings that are already linked.

Tests

• TestRunPyLovoLinkBuild_LinksEveryWayAboveThreshold: one 3D building with four ways of known confidence. It requires one primary, two further ways ordered by confidence, nothing for the way below 0.5, and the building returned once with all three ways whichever of them is asked for. On main it fails with a single link row.
• TestRunPyLovoLinkBuild_UpdatesOldLinkTable: a table in the old shape is updated by the link step and then holds both ways of one building.
• readBuildingLink in the existing link tests now reads a building's primary row, since a building can have more than one.

go vet ./..., go test -race ./... and the integration tests for process, db, importer, api and onrequest pass locally, onrequest against citydb-tool 1.3.2.

[codecov]

Codecov Report

❌ Patch coverage is 76.00000% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/process/link_table.go	65.21%	4 Missing and 4 partials ⚠️
internal/onrequest/query.go	90.47%	1 Missing and 1 partial ⚠️
internal/process/feature_extraction.go	66.66%	1 Missing and 1 partial ⚠️

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