这是我第一次使用sqlite，我编写了一个简单的数据库来存储和检索地图图块。 这是sqlite数据库：
CREATE TABLE IF NOT EXISTS Tiles (id INTEGER NOT NULL PRIMARY KEY, X INTEGER NOT NULL, Y INTEGER NOT NULL, Zoom INTEGER NOT NULL, Type INTEGER NOT NULL,Date TEXT)
CREATE TABLE IF NOT EXISTS TilesData (id INTEGER NOT NULL PRIMARY KEY CONSTRAINT fk_Tiles_id REFERENCES Tiles(id) ON DELETE CASCADE, Tile BLOB NULL)
CREATE TRIGGER fki_TilesData_id_Tiles_id BEFORE INSERT ON [TilesData] FOR EACH ROW BEGIN SELECT RAISE(ROLLBACK, 'insert on table TilesData violates foreign key constraint fki_TilesData_id_Tiles_id') WHERE (SELECT id FROM Tiles WHERE id = NEW.id) IS NULL; END
CREATE TRIGGER fku_TilesData_id_Tiles_id BEFORE UPDATE ON [TilesData] FOR EACH ROW BEGIN SELECT RAISE(ROLLBACK, 'update on table TilesData violates foreign key constraint fku_TilesData_id_Tiles_id') WHERE (SELECT id FROM Tiles WHERE id = NEW.id) IS NULL; END
CREATE TRIGGER fkdc_TilesData_id_Tiles_id BEFORE DELETE ON Tiles FOR EACH ROW BEGIN DELETE FROM TilesData WHERE TilesData.id = OLD.id; END
这是插入操作：
INSERT INTO Tiles(X, Y, Zoom, Type,Date) VALUES(?, ?, ?, ?,?);
INSERT INTO TilesData(id, Tile) VALUES((SELECT last_insert_rowid()), ?);
这是读操作：
SELECT Tile FROM TilesData WHERE id = (SELECT id FROM Tiles WHERE X=%1 AND Y=%2 AND Zoom=%3 AND Type=%4)
问题是，当数据库很小时，读取仍然非常快（大约20ms），但是当数据库变得更大（大约15000行）时，读访问变得非常慢（大约4000ms）。 我做错了吗？有任何改善表现的建议吗？