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From Doug Meil <doug.m...@explorysmedical.com>
Subject Re: HBase Types: Explicit Null Support
Date Mon, 01 Apr 2013 18:41:24 GMT

HmmmÅ  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" <ndimiduk@gmail.com> 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
>idea.
>
>The variable-width encodings have it a little easier. There's already
>enough going on that it's simpler to make room.
>
>Remember, the final goal is to support order-preserving serialization.
>This
>imposes some limitations on our encoding strategies. For instance, it's
>not
>enough to simply encode null, it really needs to be encoded as 0x00 so as
>to sort lexicographically earlier than any other value.
>
>What do you think? Any ideas, experiences, etc?
>
>Thanks,
>Nick




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