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HBase, mail # user - HBase Types: Explicit Null Support

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Re: HBase Types: Explicit Null Support
Nick Dimiduk 2013-04-01, 23:41
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?

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 <
>>>> 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
>>>> instance,
>>>> if we want to have a fixed-width signed long stored on 8-bytes, where do
>>>>> you put null? float and double types can cheat a little by folding
>>>>> negative
>>>>> and positive NaN's into a single representation (this isn't strictly
>>>>> correct!), leaving a place to represent null. In the long example case,
>>>>> the
>>>>> obvious choice is to reduce MAX_VALUE or increase MIN_VALUE by one.
>>>>> This
>>>>> will allocate an additional encoding which can be used for null. My
>>>>> experience working with scientific data, however, makes me wince at the