Merge pull request #2337 from kemege/db_charset

Add character set options when opening DB connection, default to UTF-8

lib/impure/db_mysql.nim

@@ -229,3 +229,9 @@ proc open*(connection, user, password, database: string): TDbConn {.
     var errmsg = $mysql.error(result)
     db_mysql.close(result)
     dbError(errmsg)
+
+proc setEncoding*(connection: TDbConn, encoding: string): bool {.
+  tags: [FDb].} =
+  ## sets the encoding of a database connection, returns true for 
+  ## success, false for failure.
+  result = mysql.set_character_set(connection, encoding) == 0

lib/impure/db_postgres.nim

@@ -260,3 +260,9 @@ proc open*(connection, user, password, database: string): TDbConn {.
   ## the nim db api.
   result = pqsetdbLogin(nil, nil, nil, nil, database, user, password)
   if pqStatus(result) != CONNECTION_OK: dbError(result) # result = nil
+
+proc setEncoding*(connection: TDbConn, encoding: string): bool {.
+  tags: [FDb].} =
+  ## sets the encoding of a database connection, returns true for 
+  ## success, false for failure.
+  return pqsetClientEncoding(connection, encoding) == 0

lib/impure/db_sqlite.nim

@@ -192,7 +192,19 @@ proc open*(connection, user, password, database: string): TDbConn {.
     result = db
   else:
     dbError(db)
-   
+
+proc setEncoding*(connection: TDbConn, encoding: string): bool {.
+  tags: [FDb].} =
+  ## sets the encoding of a database connection, returns true for 
+  ## success, false for failure.
+  ##
+  ## Note that the encoding cannot be changed once it's been set.
+  ## According to SQLite3 documentation, any attempt to change 
+  ## the encoding after the database is created will be silently 
+  ## ignored.
+  exec(connection, sql"PRAGMA encoding = ?", [encoding])
+  result = connection.getValue(sql"PRAGMA encoding") == encoding
+
 when isMainModule:
   var db = open("db.sql", "", "", "")
   exec(db, sql"create table tbl1(one varchar(10), two smallint)", [])