Re: [Bug 11394] New: We should throw if continue() is called with a key <= the current position

What exception should we throw?  CONSTRAINT_ERR?

On Tue, Nov 23, 2010 at 11:50 PM, <bugzilla@jessica.w3.org> wrote:

> http://www.w3.org/Bugs/Public/show_bug.cgi?id=11394
>
>           Summary: We should throw if continue() is called with a key <=
>                    the current position
>           Product: WebAppsWG
>           Version: unspecified
>          Platform: PC
>        OS/Version: All
>            Status: NEW
>          Severity: normal
>          Priority: P2
>         Component: Indexed Database API
>        AssignedTo: dave.null@w3.org
>        ReportedBy: jonas@sicking.cc
>         QAContact: member-webapi-cvs@w3.org
>                CC: mike@w3.org, public-webapps@w3.org
>
>
> (The below assumes a forward iterating cursor, opposite applies for a
> reverse
> iterating cursor of course).
>
> The spec currently states that when calling IDBCursor.continue and passing
> in a
> key, the cursor moves to the first record which is greater than the current
> position, and greater than or equal to the passed in key.
>
> As we implemented this we realized that this makes the situation when
> someone
> passes in a key which is less than or equal to the current position very
> strange. The effect is that the key argument is ignored.
>
> However most likely this was done in error. Worst case, the author might
> have
> thought that the cursor would go back to the first entry whose key is
> greater
> than or equal to the passed in key, ignoring the current position.
>
> One example of buggy code would be displaying a sales-table with 10 entries
> from every employee name. If the code ends up passing in a key which is
> less
> than or equal to the passed in key, the code likely contains an error.
>
> So a better behavior would be to throw if the passed in key is less than or
> equal to the cursors current position. This makes it more clear that an
> error
> occurred, as well as helps a debugger detect the exception and display the
> current program state.
>
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