Experimental Physics and
Industrial Control System

On 1/2/23 3:53 PM, Hu, Yong via Tech-talk wrote:

Michael, we are talking about fields here. So “det1:NELM.RTYP” itself is not valid.

If "det1" is an IOC record, then "det1.RTYP" is definitely a PV name that the IOC will respond to. "RTYP" is a record attribute that the IOC adds to all record types, which returns the name of the record type. Some CA client applications (e.g. MEDM, capr.pl, CS-Studio's pvtree) query that attribute automatically for some/all of the channels they connect to, so a field alias such as the one suggested could result in the IOC seeing requests for that PV name.

Another (less important) use case is a script I sometimes use to avoid developing OPI screens remotely.

Michael's question is thus a valid one. For a simple/naive implementation of this feature the answer might be that the channel name “det1:NELM.RTYP” would time out, and such field aliases just wouldn't support the capr.pl or pvtree applications at all in that case. That might be acceptable,

I think it is desirable to continue to support remote database "crawling", although no necessarily with RTYP alone.  Which has obvious limitations in requiring a client to encode knowledge about record types.  An alternative which I occasionally think about is adding another pseudo field which GETs a description of the record type.  eg. as a string (.dbd or some json) or equivalent PVD structure.

but I would want to be shown that any implementation would not significantly increase the amount of work that the IOC's CA Search thread has to do.

Agreed.  In both the positive and especially the negative case.

References:

Re: Possible to create aliases for record fields? Michael Davidsaver via Tech-talk

Re: Possible to create aliases for record fields? Hu, Yong via Tech-talk

Re: Possible to create aliases for record fields? Andrew Johnson via Tech-talk

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