eval evil?

On Fri, Apr 13, 2012 at 2:54 PM, Andy Bunce <bunce.andy at gmail.com> wrote: > Musing on the the usefulness of actions that update the database and return > something, specifically in a web server with Xforms context, and the absence > of XQuery scripting. I have been playing around with things like the > following: > > let $s:=util:eval(' > let $x:=copy $c:=db:open("listman","1.xml") > modify (replace value of node $c/updated with current-dateTime()) > return $c > return db:replace("listman","1.xml",$x) > ') > return db:open("listman","1.xml") > > This works, but is it likely to stop working in the future? Is there a > better way? > > /Andy > > _______________________________________________ > BaseX-Talk mailing list > BaseX-Talk at mailman.uni-konstanz.de > https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk >

> Dear Andy, > > sorry for the frightening delay! We haven't been inactive, however: > you have warmed up a frequently discussed limitation of XQuery Update, > and after a longer discussion, we found a solution that complies to > the semantics of the XQuery Update spec., but still gives you a > solution to return results from an updating query. > > The solution is a new function db:output() [1], which caches its > argument at runtime and returns the result after all update operations > have been processed. If a node is passed on as argument, it is copied > in main memory to avoid that it will be modified or deleted in a > pending update operation. The db:output() function itself is marked > "updating", which means that it can only be used in combination with > other updating operations. > > Beside that, we have now defined all functions that return no value as > "vacuous", which means they can now be used along with other updating > operations. This way, you can e.g. perform update operations and call > file:append(...) to write information to a log file in a single query. > > I have just updated our snapshots; feedback is welcome. > Christian > > [1] http://docs.basex.org/wiki/Database_Module#db:output > [2] http://docs.basex.org/wiki/Releases#Stable_Snapshots > ___________________________ > > On Fri, Apr 13, 2012 at 2:54 PM, Andy Bunce <bunce.andy at gmail.com> wrote: > > Musing on the the usefulness of actions that update the database and > return > > something, specifically in a web server with Xforms context, and the > absence > > of XQuery scripting. I have been playing around with things like the > > following: > > > > let $s:=util:eval(' > > let $x:=copy $c:=db:open("listman","1.xml") > > modify (replace value of node $c/updated with current-dateTime()) > > return $c > > return db:replace("listman","1.xml",$x) > > ') > > return db:open("listman","1.xml") > > > > This works, but is it likely to stop working in the future? Is there a > > better way? > > > > /Andy > > > > _______________________________________________ > > BaseX-Talk mailing list > > BaseX-Talk at mailman.uni-konstanz.de > > https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk > > >

On Mon, Apr 23, 2012 at 5:56 PM, Andy Bunce <bunce.andy at gmail.com> wrote: > Hi Christian, > > This looks like a clean and sufficient solution to the problem. > I will try it out and let you know how it goes. > Thanks. > /Andy > > > On Thu, Apr 19, 2012 at 4:37 PM, Christian Grün <christian.gruen at gmail.com > > wrote: > >> Dear Andy, >> >> sorry for the frightening delay! We haven't been inactive, however: >> you have warmed up a frequently discussed limitation of XQuery Update, >> and after a longer discussion, we found a solution that complies to >> the semantics of the XQuery Update spec., but still gives you a >> solution to return results from an updating query. >> >> The solution is a new function db:output() [1], which caches its >> argument at runtime and returns the result after all update operations >> have been processed. If a node is passed on as argument, it is copied >> in main memory to avoid that it will be modified or deleted in a >> pending update operation. The db:output() function itself is marked >> "updating", which means that it can only be used in combination with >> other updating operations. >> >> Beside that, we have now defined all functions that return no value as >> "vacuous", which means they can now be used along with other updating >> operations. This way, you can e.g. perform update operations and call >> file:append(...) to write information to a log file in a single query. >> >> I have just updated our snapshots; feedback is welcome. >> Christian >> >> [1] http://docs.basex.org/wiki/Database_Module#db:output >> [2] http://docs.basex.org/wiki/Releases#Stable_Snapshots >> ___________________________ >> >> On Fri, Apr 13, 2012 at 2:54 PM, Andy Bunce <bunce.andy at gmail.com> wrote: >> > Musing on the the usefulness of actions that update the database and >> return >> > something, specifically in a web server with Xforms context, and the >> absence >> > of XQuery scripting. I have been playing around with things like the >> > following: >> > >> > let $s:=util:eval(' >> > let $x:=copy $c:=db:open("listman","1.xml") >> > modify (replace value of node $c/updated with current-dateTime()) >> > return $c >> > return db:replace("listman","1.xml",$x) >> > ') >> > return db:open("listman","1.xml") >> > >> > This works, but is it likely to stop working in the future? Is there a >> > better way? >> > >> > /Andy >> > >> > _______________________________________________ >> > BaseX-Talk mailing list >> > BaseX-Talk at mailman.uni-konstanz.de >> > https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk >> > >> > >

On Sun, Apr 29, 2012 at 12:51 PM, Andy Bunce <bunce.andy at gmail.com> wrote: > Hi Christian, > > db:output() is working for me. I have put together a little blog piece about > it > http://cubeb.blogspot.co.uk/2012/04/listman.html > > /Andy > > > On Mon, Apr 23, 2012 at 5:56 PM, Andy Bunce <bunce.andy at gmail.com> wrote: >> >> Hi Christian, >> >> This looks like a clean and sufficient solution to the problem. >> I will try it out and let you know how it goes. >> Thanks. >> /Andy >> >> >> On Thu, Apr 19, 2012 at 4:37 PM, Christian Grün >> <christian.gruen at gmail.com> wrote: >>> >>> Dear Andy, >>> >>> sorry for the frightening delay! We haven't been inactive, however: >>> you have warmed up a frequently discussed limitation of XQuery Update, >>> and after a longer discussion, we found a solution that complies to >>> the semantics of the XQuery Update spec., but still gives you a >>> solution to return results from an updating query. >>> >>> The solution is a new function db:output() [1], which caches its >>> argument at runtime and returns the result after all update operations >>> have been processed. If a node is passed on as argument, it is copied >>> in main memory to avoid that it will be modified or deleted in a >>> pending update operation. The db:output() function itself is marked >>> "updating", which means that it can only be used in combination with >>> other updating operations. >>> >>> Beside that, we have now defined all functions that return no value as >>> "vacuous", which means they can now be used along with other updating >>> operations. This way, you can e.g. perform update operations and call >>> file:append(...) to write information to a log file in a single query. >>> >>> I have just updated our snapshots; feedback is welcome. >>> Christian >>> >>> [1] http://docs.basex.org/wiki/Database_Module#db:output >>> [2] http://docs.basex.org/wiki/Releases#Stable_Snapshots >>> ___________________________ >>> >>> On Fri, Apr 13, 2012 at 2:54 PM, Andy Bunce <bunce.andy at gmail.com> wrote: >>> > Musing on the the usefulness of actions that update the database and >>> > return >>> > something, specifically in a web server with Xforms context, and the >>> > absence >>> > of XQuery scripting. I have been playing around with things like the >>> > following: >>> > >>> > let $s:=util:eval(' >>> > let $x:=copy $c:=db:open("listman","1.xml") >>> > modify (replace value of node $c/updated with current-dateTime()) >>> > return $c >>> > return db:replace("listman","1.xml",$x) >>> > ') >>> > return db:open("listman","1.xml") >>> > >>> > This works, but is it likely to stop working in the future? Is there a >>> > better way? >>> > >>> > /Andy >>> > >>> > _______________________________________________ >>> > BaseX-Talk mailing list >>> > BaseX-Talk at mailman.uni-konstanz.de >>> > https://mailman.uni-konstanz.de/mailman/listinfo/basex-talk >>> > >> >> >