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CREATE TABLE resources ( -- Generic table for style, source, sprite, and glyph resources.
url TEXT NOT NULL PRIMARY KEY, -- Same schema as http_cache table.
kind INTEGER NOT NULL,
expires INTEGER,
modified INTEGER,
accessed INTEGER,
etag TEXT,
data BLOB, -- NULL if the response was a 404
compressed INTEGER NOT NULL DEFAULT 0
);
CREATE TABLE tilesets (
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
url_template TEXT NOT NULL, -- As it would appear in TileJSON (but no support for host sharding).
pixel_ratio INTEGER, -- If NULL, 1 is assumed for raster sources.
UNIQUE (url_template, pixel_ratio) -- Capable of caching the same tileset at multiple resolutions.
);
CREATE TABLE tiles (
tileset_id INTEGER NOT NULL REFERENCES tilesets(id),
z INTEGER NOT NULL, -- Fully abandon TMS coordinates in favor of ZXY.
x INTEGER NOT NULL,
y INTEGER NOT NULL,
expires INTEGER,
modified INTEGER,
accessed INTEGER,
etag TEXT,
data BLOB, -- NULL if the response was a 404
compressed INTEGER NOT NULL DEFAULT 0,
PRIMARY KEY (tileset_id, z, x, y)
);
CREATE TABLE regions (
id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
definition TEXT NOT NULL, -- JSON formatted definition of region. Regions may be of variant types:
-- e.g. bbox and zoom range, route path, flyTo parameters, etc. Note that
-- the set of tiles required for a region may span multiple sources.
description BLOB -- User provided data in user-defined format
);
CREATE TABLE region_resources (
region_id INTEGER NOT NULL REFERENCES regions(id),
resource_url TEXT NOT NULL REFERENCES resources(url),
PRIMARY KEY (region_id, resource_url)
);
CREATE TABLE region_tiles (
region_id INTEGER NOT NULL REFERENCES regions(id),
tileset_id INTEGER NOT NULL REFERENCES tilesets(id),
z INTEGER NOT NULL,
x INTEGER NOT NULL,
y INTEGER NOT NULL,
PRIMARY KEY (region_id, tileset_id, z, x, y),
FOREIGN KEY (tileset_id, z, x, y) REFERENCES tiles (tileset_id, z, x, y)
);
-- `region_resources` and `region_tiles` are used for deduplication and deletion logic.
-- A row in `tiles` exists IFF one or more corresponding rows exist in `region_tiles`. If
-- more than one corresponding row exists, it indicates multiple regions contain the tile, and
-- storage for the tile is being deduplicated. When a region is deleted, corresponding rows in
-- `region_tiles` must also be deleted, and then rows in `tiles` and `tilesets` without a
-- corresponding `region_tiles` row must be deleted. Similarly for `resources` / `region_resources`.
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