cursor.txt

The following recipe shows an error with the LuaSQL library for
SQLite3.

Tested with Debian 10.10 (buster), SQLite3 3.35.5, LuaSQL 2.6.0.

Note that the second row of the table Cursor doesn't print, and there
is a "there are open cursors" error message.

Is this a bug, or am I missing something? I don't think it's necessary
to close the cursor explicitly in this case, and even if that was the
problem, the second row should still print.

https://keplerproject.github.io/luasql/manual.html#cursor_object

> A call to fetch after the last row has already being returned will
> close the corresponding cursor.

############################################################
cursor.lua
############################################################
local luasql = require "luasql.sqlite3"

local function rows (connection, sql_statement)
   print("calling rows")
   -- retrieve a cursor
   local cursor = assert (connection:execute (sql_statement))
   return function ()
      return cursor:fetch()
   end
end

function Cursor (dbname)
   local env = assert (luasql.sqlite3())
   local con = assert (env:connect(dbname))
   for Date, Num in rows (con, string.format("select Date, Num from %s", "opencursors")) do
      print(Date, Num)
   end
   con:close()
   env:close()
end

Cursor("cursor.db")
############################################################
date.sql
############################################################
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE opencursors (
	"Date" DATE,
        "Num" NUM
);
INSERT INTO opencursors VALUES('2019-04-02', 0);
INSERT INTO opencursors VALUES(NULL, 1);
COMMIT;
############################################################
cursor.sh
############################################################
rm cursor.db
cat date.sql | sqlite3 cursor.db
lua5.3 cursor.lua
############################################################

sh cursor.sh

calling rows
2019-04-02      0
lua5.3: cursor.lua:18: LuaSQL: there are open cursors
stack traceback:
        [C]: in method 'close'
        cursor.lua:18: in function 'Cursor'
        cursor.lua:22: in main chunk
        [C]: in ?