Rewrite DB class to allow backends to fully optimize block fetches

include/TileGenerator.h

@@ -2,7 +2,8 @@
 #define TILEGENERATOR_HEADER
 
 #include <iosfwd>
-#include <list>
+#include <map>
+#include <set>
 #include <config.h>
 #include <unordered_map>
 #include <unordered_set>
@@ -64,7 +65,8 @@ public:
 	void setBgColor(const std::string &bgColor);
 	void setScaleColor(const std::string &scaleColor);
 	void setOriginColor(const std::string &originColor);
-	void setPlayerColor(const std::string &playerColor); Color parseColor(const std::string &color);
+	void setPlayerColor(const std::string &playerColor);
+	Color parseColor(const std::string &color);
 	void setDrawOrigin(bool drawOrigin);
 	void setDrawPlayers(bool drawPlayers);
 	void setDrawScale(bool drawScale);
@@ -88,7 +90,6 @@ private:
 	void loadBlocks();
 	void createImage();
 	void renderMap();
-	std::list<int16_t> getZValueList() const;
 	void renderMapBlock(const BlockDecoder &blk, const BlockPos &pos);
 	void renderMapBlockBottom(const BlockPos &pos);
 	void renderShading(int zPos);
@@ -118,19 +119,23 @@ private:
 	DB *m_db;
 	Image *m_image;
 	PixelAttributes m_blockPixelAttributes;
+	/* smallest/largest seen X or Z block coordinate */
 	int m_xMin;
 	int m_xMax;
 	int m_zMin;
 	int m_zMax;
+	/* Y limits for rendered area (node units) */
 	int m_yMin;
 	int m_yMax;
-	int m_geomX;
-	int m_geomY;
-	int m_geomX2;
-	int m_geomY2;
+	/* limits for rendered area (block units) */
+	int16_t m_geomX;
+	int16_t m_geomY; /* Y in terms of rendered image, Z in the world */
+	int16_t m_geomX2;
+	int16_t m_geomY2;
+	/* */
 	int m_mapWidth;
 	int m_mapHeight;
-	std::list<std::pair<int16_t, int16_t>> m_positions;
+	std::map<int16_t, std::set<int16_t>> m_positions; /* indexed by Z, contains X coords */
 	ColorMap m_colorMap;
 	BitmapThing m_readPixels;
 	BitmapThing m_readInfo;

include/db-leveldb.h

@@ -2,19 +2,25 @@
 #define DB_LEVELDB_HEADER
 
 #include "db.h"
+#include <unordered_map>
+#include <utility>
 #include <leveldb/db.h>
 
 class DBLevelDB : public DB {
 public:
 	DBLevelDB(const std::string &mapdir);
-	virtual std::vector<BlockPos> getBlockPos();
-	virtual void getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos);
-	virtual ~DBLevelDB();
+	std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) override;
+	void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
+			int16_t min_y, int16_t max_y) override;
+	~DBLevelDB() override;
+
 private:
+	using pos2d = std::pair<int16_t, int16_t>;
+
 	void loadPosCache();
 
-	std::vector<BlockPos> posCache;
-
+	// indexed by Z, contains all (x,y) position pairs
+	std::unordered_map<int16_t, std::vector<pos2d>> posCache;
 	leveldb::DB *db;
 };
 

include/db-postgresql.h

@@ -7,9 +7,11 @@
 class DBPostgreSQL : public DB {
 public:
 	DBPostgreSQL(const std::string &mapdir);
-	virtual std::vector<BlockPos> getBlockPos();
-	virtual void getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos);
-	virtual ~DBPostgreSQL();
+	std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) override;
+	void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
+		int16_t min_y, int16_t max_y) override;
+	~DBPostgreSQL() override;
+
 protected:
 	PGresult *checkResults(PGresult *res, bool clear = true);
 	void prepareStatement(const std::string &name, const std::string &sql);
@@ -17,11 +19,11 @@ protected:
 		const char *stmtName, const int paramsNumber,
 		const void **params,
 		const int *paramsLengths = NULL, const int *paramsFormats = NULL,
-		bool clear = true, bool nobinary = true
+		bool clear = true
 	);
-	int pg_to_int(PGresult *res, int row, int col);
 	int pg_binary_to_int(PGresult *res, int row, int col);
 	BlockPos pg_to_blockpos(PGresult *res, int row, int col);
+
 private:
 	PGconn *db;
 };

include/db-redis.h

@@ -2,21 +2,27 @@
 #define DB_REDIS_HEADER
 
 #include "db.h"
+#include <unordered_map>
+#include <utility>
 #include <hiredis/hiredis.h>
 
 class DBRedis : public DB {
 public:
 	DBRedis(const std::string &mapdir);
-	virtual std::vector<BlockPos> getBlockPos();
-	virtual void getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos);
-	virtual ~DBRedis();
+	std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) override;
+	void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
+		int16_t min_y, int16_t max_y) override;
+	~DBRedis() override;
+
 private:
+	using pos2d = std::pair<int16_t, int16_t>;
 	static std::string replyTypeStr(int type);
 
 	void loadPosCache();
 	void HMGET(const std::vector<BlockPos> &positions, std::vector<ustring> *result);
 
-	std::vector<BlockPos> posCache;
+	// indexed by Z, contains all (x,y) position pairs
+	std::unordered_map<int16_t, std::vector<pos2d>> posCache;
 
 	redisContext *ctx;
 	std::string hash;

include/db-sqlite3.h

@@ -2,19 +2,30 @@
 #define _DB_SQLITE3_H
 
 #include "db.h"
+#include <unordered_map>
 #include <sqlite3.h>
 
 class DBSQLite3 : public DB {
 public:
 	DBSQLite3(const std::string &mapdir);
-	virtual std::vector<BlockPos> getBlockPos();
-	virtual void getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos);
-	virtual ~DBSQLite3();
+	std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) override;
+	void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
+			int16_t min_y, int16_t max_y) override;
+	~DBSQLite3() override;
+
 private:
+	inline void getPosRange(int64_t &min, int64_t &max, int16_t zPos,
+			int16_t zPos2) const;
+	void loadBlockCache(int16_t zPos);
+
 	sqlite3 *db;
 
 	sqlite3_stmt *stmt_get_block_pos;
+	sqlite3_stmt *stmt_get_block_pos_z;
 	sqlite3_stmt *stmt_get_blocks_z;
+
+	int16_t blockCachedZ = -10000;
+	std::unordered_map<int16_t, BlockList> blockCache; // indexed by X
 };
 
 #endif // _DB_SQLITE3_H

include/db.h

@@ -5,7 +5,6 @@
 #include <map>
 #include <list>
 #include <vector>
-#include <string>
 #include <utility>
 #include "types.h"
 
@@ -17,6 +16,8 @@ struct BlockPos {
 
 	BlockPos() : x(0), y(0), z(0) {}
 	BlockPos(int16_t x, int16_t y, int16_t z) : x(x), y(y), z(z) {}
+
+	// Implements the inverse ordering so that (2,2,2) < (1,1,1)
 	bool operator < (const BlockPos &p) const
 	{
 		if (z > p.z)
@@ -42,13 +43,21 @@ typedef std::list<Block> BlockList;
 
 class DB {
 protected:
+	// Helpers that implement the hashed positions used by most backends
 	inline int64_t  encodeBlockPos(const BlockPos pos) const;
 	inline BlockPos decodeBlockPos(int64_t hash) const;
 
 public:
-	virtual std::vector<BlockPos> getBlockPos() = 0;
-	virtual void getBlocksOnZ(std::map<int16_t, BlockList> &blocks, int16_t zPos) = 0;
-	virtual ~DB() {};
+	/* Return all block positions inside the range given by min and max,
+	 * so that min.x <= x < max.x, ...
+	 */
+	virtual std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) = 0;
+	/* Return all blocks in column given by x and z
+	 * and inside the given Y range (min_y <= y < max_y)
+	 */
+	virtual void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
+			int16_t min_y, int16_t max_y) = 0;
+	virtual ~DB() {}
 };