Description | TileMill создаёт следующие таблицы:
CREATE TABLE grid_key (
grid_id TEXT,
key_name TEXT
);
CREATE UNIQUE INDEX grid_key_lookup ON grid_key (grid_id, key_name);
CREATE TABLE grid_utfgrid (
grid_id TEXT,
grid_utfgrid BLOB
);
CREATE UNIQUE INDEX grid_utfgrid_lookup ON grid_utfgrid (grid_id);
CREATE TABLE images (
tile_data blob,
tile_id text
);
CREATE UNIQUE INDEX images_id ON images (tile_id);
CREATE TABLE keymap (
key_name TEXT,
key_json TEXT
);
CREATE UNIQUE INDEX keymap_lookup ON keymap (key_name);
CREATE TABLE map (
zoom_level INTEGER,
tile_column INTEGER,
tile_row INTEGER,
tile_id TEXT,
grid_id TEXT
);
CREATE UNIQUE INDEX map_index ON map (zoom_level, tile_column, tile_row);
CREATE TABLE metadata (
name text,
value text
);
CREATE UNIQUE INDEX name ON metadata (name);
А для того, чтобы это всё походило на MBTiles формат, создаются 3 вьюхи:
CREATE VIEW grid_data AS
SELECT
map.zoom_level AS zoom_level,
map.tile_column AS tile_column,
map.tile_row AS tile_row,
keymap.key_name AS key_name,
keymap.key_json AS key_json
FROM map
JOIN grid_key ON map.grid_id = grid_key.grid_id
JOIN keymap ON grid_key.key_name = keymap.key_name;
CREATE VIEW grids AS
SELECT
map.zoom_level AS zoom_level,
map.tile_column AS tile_column,
map.tile_row AS tile_row,
grid_utfgrid.grid_utfgrid AS grid
FROM map
JOIN grid_utfgrid ON grid_utfgrid.grid_id = map.grid_id;
CREATE VIEW tiles AS
SELECT
map.zoom_level AS zoom_level,
map.tile_column AS tile_column,
map.tile_row AS tile_row,
images.tile_data AS tile_data
FROM map
JOIN images ON images.tile_id = map.tile_id;
Тайлы сохраняются в таблицу images, а в качестве id используется md5 хэш от тела тайла. Координаты тайлов (X, Y, Z) сохраняются в таблицу map. Таблица metadata содержит поля: bounds, minzoom, maxzoom, attribution, description, name, template (пустое), version '1.0.0'. Остальные таблицы пустые.
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