Dave --
I think this topic is pretty well exhausted, empty strings will be
nulled and null property values will not be written or at least voided. Either
the form controller or the user is responsible for putting in "Unknown" or a
similar appropriate value if there's a required property whose value is not
known. I think the only remaining question is whether this is done in the save
method or via AOP.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Dave Thomas
Sent: Monday, September 26, 2011 1:53 PM
To: [email protected]
Subject: Re: [OPENMRS-DEV] Empty string fields vs null fields
sorry to jump into this discussion late, and maybe with a lame,
already-covered comment.
i would say that maybe 10-15% of our sync traffic are
patientAttributes with value '''. (empty string), which are totally
meaningless rows that are basically just feeding MTN money for
bandwidth. It would be nice if in the design process we could
minimize these. Do we even really need attribute rows where value =
NULL?, or can we at least get rid of the ones that really don't mean
anything?
d
On Sun, Sep 25, 2011 at 8:18 PM, Darius Jazayeri
<[email protected]> wrote:
> Multiplicity constraints on attributes are enforced by the validator of the
> class that owns those attributes. I.e. if you have a VisitAttributeType with
> minOccurs=1 and maxOccurs=3, that will be checked when you validate the
> Visit it belongs to.
> I'd hope things would work like this:
> (1) visit.setAttribute(attrType, null) --> semantically equivalent to "void
> any existing attributes of the given type"
> (2) visit.addAttribute(attrType, null) --> this should fail when you try to
> save the visit, because a null-valued attribute is invalid. (The db has a
> not-null constraint on the value column.) To get a pretty error in this
> case, we'd probably need to handle this in the controller for the edit visit
> page. But at least the AOP would prevent us from storing empty values for
> attributes (unintentionally sidestepping the not-null constraint.)
> -Darius
> On Sun, Sep 25, 2011 at 8:09 AM, Friedman, Roger (CDC/CGH/DGHA) (CTR)
> <[email protected]> wrote:
>>
>> I actually agree that something should be put in the field, but I have
>> seen so many variants (blank, ?, ??, ???, Unknown, Uknown, Unown, Not Known,
>> Not Available, Missing, Left Card At Home) that I have come to believe that
>> the easiest thing to say to users is "if you don't know it, leave it
>> blank". The form controller normally will know whether an unknown value is
>> required and if so what its representation should be; however, that doesn't
>> apply to our 3 formentry modules. In the case of OpenMRS objects, we could
>> use ID=-1 to indicate unknown, perhaps providing a default entry in the
>> underlying table (to permit inner rather than left joins).
>>
>>
>>
>> But you still haven't said where the multiplicity constraints on
>> attributes should be enforced and whether that's compatible with using AOP
>> to convert empty strings to nulls and what the effect of updating an
>> attribute value to null should be.
>>
>>
>>
>> From: [email protected] [mailto:[email protected]] On Behalf Of Darius
>> Jazayeri
>> Sent: Friday, September 23, 2011 2:44 PM
>>
>> To: [email protected]
>> Subject: Re: [OPENMRS-DEV] Empty string fields vs null fields
>>
>>
>>
>> I agree with Burke here, I think that allowing people to store "" in a
>> required field, and using that to represent "yes, but unknown" isn't right.
>> You should store an explicit and recognizable unknown value, e.g. "Unknown".
>> So for the guardian case, no guardian means do not store a row in the
>> person_attribute table for the non-existent guardian. And an
>> existent-but-unknown guardian would be stored as an attribute whose value is
>> a pointer to an "Unknown Person" person.
>>
>>
>>
>> Also, at a web UI level, the standard widgets don't distinguish between
>> these things (i.e. if you have an attribute type whose datatype is "person",
>> the out-of-the-box widget is just going to show a person chooser, not have
>> an extra "click for unknown")...
>>
>>
>>
>> -Darius
>>
>> On Friday, September 23, 2011, Burke Mamlin wrote:
>>
>> Roger,
>>
>>
>>
>> As you suggest, treating all empty strings as null will enforce that
>> required fields cannot be blank, since we won't be able to distinguish
>> between answered with an empty string from not answered at all. That said,
>> when is it "okay" to respond to a required question with nothing? Wouldn't
>> your example be better handled by recording the "Unknown" (in the case that
>> the orphan has a legal guardian who is currently unknown) instead of
>> treating unknown the same as if the field were skipped? And/or record "N/A"
>> when the field doesn't apply (in OpenMRS, we would probably just omit
>> storing an observation altogether if it didn't apply).
>>
>>
>>
>> -Burke
>>
>> On Fri, Sep 23, 2011 at 8:59 AM, Friedman, Roger (CDC/CGH/DGHA) (CTR)
>> <[email protected]> wrote:
>>
>> Darius -
>>
>> I believe I gave several examples during the earlier round of this
>> discussion. Here's one - an orphan has a legal guardian, but the person
>> bringing the orphan to the clinic doesn't know who, so the field is left
>> blank; a non-orphan does not have a legal guardian. So when it comes time
>> to report, you do something patient left join person_attribute where
>> attribute_type="Legal Guardian" and format the nulls as "N/A" and print the
>> empty strings.
>>
>> I don't think the automagic works with the new attribute paradigm.
>> Take a required attribute like National ID. The patient does have her card
>> with her when she comes to the clinic. Now we can't save the patient info.
>> So I withdraw my tentative conclusion about properties. Is the
>> implementation of the minimum constraint still undecided? Let's make sure
>> that's well-understood before moving on to automagic.
>>
>>
>>
>> From: [email protected] [mailto:[email protected]] On Behalf Of Darius
>> Jazayeri
>> Sent: Thursday, September 22, 2011 4:36 PM
>>
>> To: [email protected]
>> Subject: Re: [OPENMRS-DEV] Empty string fields vs null fields
>>
>>
>>
>> https://tickets.openmrs.org/browse/TRUNK-2680
>>
>> On Thu, Sep 22, 2011 at 1:24 PM, Darius Jazayeri <[email protected]>
>> wrote:
>>
>> There is already AOP happening on every XyzService.saveXyz call. So we're
>> actually already paying the significant overhead. I think that
>> reflection+iterating over properties only on saveXyz methods is vanishingly
>> small additional overhead to the fact that every service call is AOPd.
>>
>>
>>
>> -Darius
>>
>>
>>
>> On Thu, Sep 22, 2011 at 12:51 PM, Burke Mamlin <[email protected]>
>> wrote:
>>
>> On Thu, Sep 22, 2011 at 3:03 PM, Darius Jazayeri <[email protected]>
>> wrote:
>>
>> So, does that mean you're fine with automagically changing empty String
>> properties of OpenmrsObjects to null before saving to the database?
>>
>>
>>
>> Yes. I love magic (I'm no muggle!). as long as it's not going to add
>> several milliseconds or more to every API call. If doing it automagically
>> involves AOP or some other hook that is going to add (or contribute to) a
>> measurable performance hit, I would rather find a way to manage it
>> explicitly (via hibernate configuration, a custom hibernate type, and/or
>> code reviews).
>>
>>
>>
>> -Burke
>>
>>
>>
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