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HBase >> mail # user >> HBase Types: Explicit Null Support


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Re: HBase Types: Explicit Null Support
On 04/01/2013 04:41 PM, Nick Dimiduk wrote:
> On Mon, Apr 1, 2013 at 4:31 PM, James Taylor <[EMAIL PROTECTED]> wrote:
>
>>  From the SQL perspective, handling null is important.
>
>  From your perspective, it is critical to support NULLs, even at the expense
> of fixed-width encodings at all or supporting representation of a full
> range of values. That is, you'd rather be able to represent NULL than -2^31?
We've been able to get away with supporting NULL through the absence of
the value rather than restricting the data range. We haven't had any
push back on not allowing a fixed width nullable leading row key column.
Since our variable length DECIMAL supports null and is a superset of the
fixed width numeric types, users have a reasonable alternative.

I'd rather not restrict the range of values, since it doesn't seem like
this would be necessary.
>
> On 04/01/2013 01:32 PM, Nick Dimiduk wrote:
>>> Thanks for the thoughtful response (and code!).
>>>
>>> I'm thinking I will press forward with a base implementation that does not
>>> support nulls. The idea is to provide an extensible set of interfaces, so
>>> I
>>> think this will not box us into a corner later. That is, a mirroring
>>> package could be implemented that supports null values and accepts
>>> the relevant trade-offs.
>>>
>>> Thanks,
>>> Nick
>>>
>>> On Mon, Apr 1, 2013 at 12:26 PM, Matt Corgan <[EMAIL PROTECTED]> wrote:
>>>
>>>   I spent some time this weekend extracting bits of our serialization code
>>>> to
>>>> a public github repo at http://github.com/hotpads/**data-tools<http://github.com/hotpads/data-tools>
>>>> .
>>>>    Contributions are welcome - i'm sure we all have this stuff laying
>>>> around.
>>>>
>>>> You can see I've bumped into the NULL problem in a few places:
>>>> *
>>>>
>>>> https://github.com/hotpads/**data-tools/blob/master/src/**
>>>> main/java/com/hotpads/data/**primitive/lists/LongArrayList.**java<https://github.com/hotpads/data-tools/blob/master/src/main/java/com/hotpads/data/primitive/lists/LongArrayList.java>
>>>> *
>>>>
>>>> https://github.com/hotpads/**data-tools/blob/master/src/**
>>>> main/java/com/hotpads/data/**types/floats/DoubleByteTool.**java<https://github.com/hotpads/data-tools/blob/master/src/main/java/com/hotpads/data/types/floats/DoubleByteTool.java>
>>>>
>>>> Looking back, I think my latest opinion on the topic is to reject
>>>> nullability as the rule since it can cause unexpected behavior and
>>>> confusion.  It's cleaner to provide a wrapper class (so both
>>>> LongArrayList
>>>> plus NullableLongArrayList) that explicitly defines the behavior, and
>>>> costs
>>>> a little more in performance.  If the user can't find a pre-made wrapper
>>>> class, it's not very difficult for each user to provide their own
>>>> interpretation of null and check for it themselves.
>>>>
>>>> If you reject nullability, the question becomes what to do in situations
>>>> where you're implementing existing interfaces that accept nullable
>>>> params.
>>>>    The LongArrayList above implements List<Long> which requires an
>>>> add(Long)
>>>> method.  In the above implementation I chose to swap nulls with
>>>> Long.MIN_VALUE, however I'm now thinking it best to force the user to
>>>> make
>>>> that swap and then throw IllegalArgumentException if they pass null.
>>>>
>>>>
>>>> On Mon, Apr 1, 2013 at 11:41 AM, Doug Meil <
>>>> [EMAIL PROTECTED]
>>>>
>>>>> wrote:
>>>>> HmmmŠ good question.
>>>>>
>>>>> I think that fixed width support is important for a great many rowkey
>>>>> constructs cases, so I'd rather see something like losing MIN_VALUE and
>>>>> keeping fixed width.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 4/1/13 2:00 PM, "Nick Dimiduk" <[EMAIL PROTECTED]> wrote:
>>>>>
>>>>>   Heya,
>>>>>> Thinking about data types and serialization. I think null support is an
>>>>>> important characteristic for the serialized representations, especially
>>>>>> when considering the compound type. However, doing so in directly
>>>>>> incompatible with fixed-width representations for numerics. For