R/sqlFetchMore.R

In zozlak/RODBCext: Parameterized Queries Extension for RODBC

# Copyright (C) 2014 Mateusz Zoltak
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 or 3 of the License
#  (at your option).
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  http://www.r-project.org/Licenses/

#' @title Overlay over \link[RODBC]{sqlFetchMore} 
#' @useDynLib RODBCext
#' @import RODBC
#' @description
#' RODBC::sqlFetchMore crashes if the ODBC channel is in "query prepared
#' but already not executed" state.
#' This function is a small overlay emmitting an error in such a case.
#' @param channel ODBC connection obtained by \link{odbcConnect}
#' @param ... other parametrs passed to \link[RODBC]{sqlFetchMore}
#' @return see \link[RODBC]{sqlFetchMore}
#' @export
sqlFetchMore = function(channel, ...)
{
  stopifnot(odbcValidChannel(channel))
  
  res = .Call("RODBCQueryStatus", attr(channel, "handle_ptr"))
  
  if (res == -1) {
    stop('an error occured')
  } else if(res == 0) {
    stop('query is prepared but not executed, you must execute it first')
  }
  
  return(RODBC::sqlFetchMore(channel, ...))
}