[OASIS Issue Tracker] Commented: (ODATA-166) Inconsistent lifted operators for $filter

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    [ http://tools.oasis-open.org/issues/browse/ODATA-166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=31986#action_31986 ] 

Michael Pizzo commented on ODATA-166:
-------------------------------------

The problem with 3-value logic, or with having a different operator for null, is that it makes building predicates that account for null values much harder.

For example, a query to see if a certain item had changed might build a query with a predicate checking to see if each property is equal to the previously fetched value; for example, the predicate:

$filter=FirstName eq 'Matthew' and LastName eq 'Borges' and Company eq 'SAP'

could easily be built by looping through the properties and writing propertyName "eq" value. 

Parameterized, you could write a single predicate that would work for any entity in the entityset:

String.Format("FirstName eq '{0}' and LastName eq '{1}' and Company eq '{2}'", record.FirstName, record.LastName, record.Company)

This works for null values of FirstName, LastName, and Company IFyou support <nullvalue> eq null. However, if you need a special "is null" operator, or if comparing null values is always unknown, you have to understand, contemplate, and write significantly more logic to deal with potential null values.

> Inconsistent lifted operators for $filter
> -----------------------------------------
>
>                 Key: ODATA-166
>                 URL: http://tools.oasis-open.org/issues/browse/ODATA-166
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Bug
>          Components: OData Protocol v1.0
>    Affects Versions: WD01
>         Environment: [Proposed]
>            Reporter: Matthew Borges
>            Priority: Minor
>             Fix For: WD01
>
>
> I didn't see any mention of lifted operators in the working drafts.  We should define how each operator behaves when one (or both) operands is null.
> With that said, the V3 spec (section 2.2.3.6.1.1.5) is inconsistent with it's treatment of null:
> - For equality operators, null eq null is true and null eq <anything not null> is false (i.e. the result is true or false)
> - Any relational operators when compared with null are false (i.e. the result is true or false)
>    - This implies that null ge null and null le null is false which is inconsistent with null eq null is true
> - Logical operators treat null as false (i.e. the result is true or false)
> - Unary operators are null if the operand is null (i.e. in the case of not, the result is true, false, or null)

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