pvget, pvxget and pvxs interoperability and differences

["Gotz, Malte via Tech-talk" <tech-talk at aps.anl.gov>]

Hi tech-talkers,

 

in using QSRV2 from pvxs I encountered several unexpected (for me) differences between pvget and pvxget.

I created a pva group in an IOC database as an NTTable. I'll use the example from the PVXS documentation as a minimal example (see here: https://epics-base.github.io/pvxs/qgroup.html#database-listing).

I used EPICS Base 7.0.10 and PVXS 1.5.1 to create a minimal IOC, with only base and pvxs.

 

I want to read only a single column from the table like:

pvxget -r "value.A" TST:Tbl

 

This works with pvxget, but not with pvget. Using pvget I simply get:

TST:Tbl <undefined>

A B

 

Is that expected behavior, did I miss some configuration or this a bug? If it is a bug, where should this be raised first?

 

Less critical, when constructing more complex requests, like selecting multiple columns from a single table, the syntax between the two differs. Is that intended?

For example:

pvget -r "field(value{LMT_l,LTM_h}) BPMZ1D1R:signals:sa:pva

 

works, same thing with pvxget gives me "Error: invalid character near: {LMT_l,LTM_h})"

Conversely, a working request for pvxget is

pvxget -r "field(value.LMT_l,value.LTM_h)" BPMZ1D1R:signals:sa:pva

 

When doing the same with pvget, it complains: "failed to parse request string: Can't construct Structure, duplicate fieldName value"

 

I was under the impression that pvxs is the more forward-looking implementation and one could/should use it in an IOC. While for the command line tools pvAccessCPP is the recommend way (at least it says so in the pvxs documentation). How are others handling this and what could I do to resolve these issues?

Cheers,

Malte

 

 

--------------

Dr. Malte Gotz

Phone: +49 030 8062 15808

 

Accelerator Operation  - Control System Group

(BE-IA-AOT/ACS)

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

 

Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.

 

Aufsichtsrat: Vorsitzender Michael Zimmermann, stv. Vorsitzende Dr. Jutta Koch-Unterseher

Geschäftsführung: Prof. Dr. Bernd Rech, Saskia Vormfelde

 

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Deutschland

 

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