GpkgTileRevalidation

Worldwind-private side table that holds per-tile cache freshness metadata: the HTTP ETag and Last-Modified validators (so cache refreshes can issue conditional If-None-Match / If-Modified-Since requests and the server can answer 304 to skip the body), plus validatedAt — epoch-millis the tile was last confirmed fresh against the server.

validatedAt is the stale-while-revalidate trigger: when now - validatedAt exceeds the eviction staleAfter, a background refresh fires. It is bumped on a fresh download AND on a 304, so a still-current tile doesn't get re-requested until the next window. It lives here, not as a last_modified column on the OGC tile-user-data table, so the standard table stays pristine.

Not part of the OGC GeoPackage standard — external readers see an unknown table and ignore it. The ww_ author prefix deliberately stays off the spec-reserved gpkg_ namespace. (An earlier build wrote a gpkg_tile_revalidation table; this rename starts a fresh schema rather than migrating it — see GeoPackage.writeTileRevalidation — so any such legacy table is just left orphaned, and freshness self-heals on first read.)

Keyed by (tpudt_name, tpudt_id) — the tile-pyramid-user-data table name plus the id of the tile's row in it — exactly like the OGC gpkg_2d_gridded_tile_ancillary table (and this repo's GriddedTile usage). A compact 2-column unique combo; id is just an autoincrement rowid alias (free in SQLite). The combo's leading tpudt_name column also serves the per-content bulk delete in GeoPackage.clearTileRevalidation. Tile ids are stable across rewrites (the tile row is reused), and anything missed self-heals on first read.

CREATE TABLE IF NOT EXISTS ww_tile_revalidation (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  tpudt_name TEXT NOT NULL,    -- tile-pyramid-user-data table name
  tpudt_id   INTEGER NOT NULL, -- id of the tile's row in that table
  etag       TEXT,
  http_last_modified TEXT,
  validated_at INTEGER,
  UNIQUE (tpudt_name, tpudt_id)
)