Thanks Przemek. Could you post back here when I should get the SVN etc?
Thank you for your hard work 2010/2/3 Przemysław Czerpak <dru...@acn.waw.pl> > On Tue, 02 Feb 2010, smu johnson wrote: > > Hi, > > > When a table's index file is re-opened (it was previously created), does > it > > have to evaluate the FOR clause, or can it wait to do that only when a > value > > in the table row changes? > > It does not need to be evaluated and can wait but it has to be valid > expression which can be compiled by macrocompiler. > Anyhow few times people asked to make such test evaluation to detect > some potential problems like missing functions, incompatible aliases > or not logical results as fast as possible and report RTE before > executed code will start some operations which cannot be finished. > Just like someone asked to delay all such tests as long as possible > because he only wanted to skip using the index created by foreign > application with unknown UDFs in KEY and FOR expressions. > In clipper this behavior depends on used RDD and different RDDs > evaluates KEY and FOR expressions first time in different places. > Similar situation is in xHarbour. > > > In SIX, it does not check the FOR expression when it opens an index file. > > In Harbour, when you open the index file it will evaluate the FOR > > expression, and if any variables or functions in that expression are not > > visible, the system will crash (undefined variable/function). > > Not crash but generates RTE. You can catch RT errors using BEGIN SEQUENCE > statement.You are right about FOR expression. Harbour DBFCDX evaluates > index KEY and FOR expressions to test their results just after opening > index file. It's CL5.3 DBFCDX / COMIX behavior but CL5.2 DBFCDX / SIXCDX > evaluates only KEY expression when index is open and FOR is evaluated only > when index is updated. > > > eg. Index on iif(x=3,"a","b") tag "temp" of test.cdx > > When the index is opened (set index to...) if X is not visible, Harbour > will > > crash. In Clipper, it will only crash if a row in the table changes > value > > and the index needs to be updated. > > Yes but please use more precise description. RTE is not a crash but > exception which can be fully controlled by programmer. Some important > Clipper features are implemented using RTE, i.e. NETERR() or division > by 0. > > > Unfortunately, my code has lots of specialized temporary indexes that are > > created and then used within a specific function. This does not present a > > problem until a timer event fires, which needs to close files to do > > "something". Upon reopening those file before RETURNing back the original > > function, the system crashes because the FOR in the index has variables > out > > of scope. > > I can rewrite these but I will probably have to use Private variables and > > non-Static functions. > > I'll change early expression evaluation in Harbour SIXCDX driver only > so Harbour SIXCDX will work like CL52 DBFCDX / SIX3 SIXCDX and > Harbour DBFCDX will work like CL53 DBFCDX / COMIX verifying both KEY > and FOR expressions when index is opening. > > I'll commit it in a while. You should take current Harbour SVN and > rebuild the compiler binaries. > > best regards, > Przemek > _______________________________________________ > Harbour mailing list (attachment size limit: 40KB) > Harbour@harbour-project.org > http://lists.harbour-project.org/mailman/listinfo/harbour > -- smu johnson <smujohn...@gmail.com>
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