build rudimentary postgresq block client

common/clientfactory.go

@@ -13,6 +13,13 @@ type DBClientCreator func() (DBClient, error)
 
 func CreateDBClientCreator(host string, port int) DBClientCreator {
 
+	if strings.HasPrefix(host, "postgres:") {
+		host = host[len("postgres:"):]
+		return func() (DBClient, error) {
+			return NewPGClient(host)
+		}
+	}
+
 	var address string
 	if strings.ContainsRune(host, '/') {
 		address = host

common/dbclient.go

@@ -1,9 +1,9 @@
-package common
-
 // Copyright 2022 by Sascha L. Teichmann
 // Use of this source code is governed by the MIT license
 // that can be found in the LICENSE file.
 
+package common
+
 type DBClient interface {
 	QueryCuboid(cuboid Cuboid, fn func(*Block) *Block) (count int, err error)
 	Close() error

common/pgclient.go

@@ -0,0 +1,98 @@
+// Copyright 2022 by Sascha L. Teichmann
+// Use of this source code is governed by the MIT license
+// that can be found in the LICENSE file.
+
+package common
+
+import (
+	"context"
+	"database/sql"
+
+	_ "github.com/jackc/pgx/v4/stdlib"
+)
+
+const queryCuboidSQL = `
+SELECT posx, posy, posz, data FROM blocks
+WHERE
+  posx BETWEEN $1 AND $2 AND
+  posy BETWEEN $3 AND $4 AND
+  posz BETWEEN $5 AND $6`
+
+type PGClient struct {
+	db              *sql.DB
+	queryCuboidStmt *sql.Stmt
+}
+
+func NewPGClient(connS string) (*PGClient, error) {
+	db, err := sql.Open("pgx", connS)
+	if err != nil {
+		return nil, err
+	}
+	stmt, err := db.Prepare(queryCuboidSQL)
+	if err != nil {
+		return nil, err
+	}
+	client := PGClient{
+		db:              db,
+		queryCuboidStmt: stmt,
+	}
+	return &client, nil
+}
+
+func (pgc *PGClient) QueryCuboid(
+	cuboid Cuboid,
+	fn func(*Block) *Block,
+) (int, error) {
+
+	rows, err := pgc.queryCuboidStmt.QueryContext(
+		context.Background(),
+		cuboid.P1.X, cuboid.P2.X,
+		cuboid.P1.Y, cuboid.P2.Y,
+		cuboid.P1.Z, cuboid.P2.Z)
+
+	if err != nil {
+		return 0, err
+	}
+	defer rows.Close()
+
+	var (
+		posX, posY, posZ int
+		data             []byte
+		count            int
+		block            *Block
+	)
+
+	for ; rows.Next(); count++ {
+		if err := rows.Scan(
+			&posX, &posY, posZ,
+			&data,
+		); err != nil {
+			return count, err
+		}
+		c := Coord{
+			X: int16(posX),
+			Y: int16(posY),
+			Z: int16(posZ),
+		}
+
+		if block == nil {
+			block = &Block{Coord: c, Data: data}
+		} else {
+			*block = Block{Coord: c, Data: data}
+		}
+		if block = fn(block); block != nil {
+			data = block.Data[:0]
+		} else {
+			data = nil
+		}
+	}
+
+	return count, rows.Err()
+}
+
+func (pgc *PGClient) Close() error {
+	if pgc.queryCuboidStmt != nil {
+		pgc.queryCuboidStmt.Close()
+	}
+	return pgc.db.Close()
+}