Forum OpenACS Development: Re: db_1row default return

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5: Re: db_1row default return (response to 4)
Posted by Gustaf Neumann on

you wrote: "avoid catch ?"

Yes, avoiding catch is in general a good strategy. One thing is replace the all-exceptions-swallowing catch by an ad_try, at least in situations, where meaningful error codes are used (which is not the case for current db_* commands).

But notice that this exception is only raised by by db_1row, the function db_0or1row returns exactly such a value expressing success or failure. Follow these guidelines:

  • SQL query has to return exactly 1 tuple: db_1row - otherwise something is broken
  • SQL query may return at most 1 tuple: db_0or1row - both outcomes are permissible
  • all other cases see previous post in this thread

Concerning error with lmap: Until about tree years ago, OpenACS hat an ad_proc named lmap, which was nowhere used, but conflicts with the Tcl 8.6 built in with the same name (released 2012) [1]. Therefore, the proc was move to the acs-outdated package. Your error indicates that you are using such an old version or you are requiring acs-outdated. You should consider updating.

Below is a simple version of lmap implemented by Richard Suchenwirth. If you overload the lmap in your system with this version, the error will go away.


proc lmap {_var list body} {
    upvar 1 $_var var
    set res {}
    foreach var $list {lappend res [uplevel 1 $body]}
    set res
}

[1] https://www.tcl.tk/man/tcl/TclCmd/lmap.htm