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From Emilio Lahr-Vivaz <>
Subject Re: buffer alignment (format/java/js)
Date Tue, 08 Aug 2017 13:18:38 GMT
Hi Wes,

You're right, I just realized that. I think the alignment issue might be 
in some unrelated code, actually. From what I can tell the the arrow 
writers are aligning buffers correctly; if not I'll open a bug.



On 08/08/2017 09:15 AM, Wes McKinney wrote:
> hi Emilio,
>  From your description, it isn't clear why 8-byte alignment is causing
> a problem (as compare with 64-byte alignment). My understanding is
> that JavaScript's TypedArray classes range in size from 1 to 8 bytes.
> The starting offset for all buffers should be 8-byte aligned, if not
> that is a bug. Could you clarify?
> - Wes
> On Tue, Aug 8, 2017 at 8:52 AM, Emilio Lahr-Vivaz <> wrote:
>> After looking at it further, I think only the buffers themselves need to be
>> aligned, not the metadata and/or schema. Would there be any problem with
>> changing the alignment to 64 bytes then?
>> Thanks,
>> Emilio
>> On 08/08/2017 08:08 AM, Emilio Lahr-Vivaz wrote:
>>> I'm looking into buffer alignment in the java writer classes. Currently
>>> some files written with the java streaming writer can't be read due to the
>>> javascript TypedArray's restriction that the start offset of the array must
>>> be a multiple of the data size of the array type (i.e. Int32Vectors must
>>> start on a multiple of 4, Float64Vectors must start on a multiple of 8,
>>> etc). From a cursory look at the java writer, I believe that the schema that
>>> is written first is not aligned at all, and then each record batch pads out
>>> its size to a multiple of 8. So:
>>> 1. should the schema block pad itself so that the first record batch is
>>> aligned, and is there any problem with doing so?
>>> 2. is there any problem with changing the alignment to 64 bytes, as
>>> recommended (but not required) by the spec?
>>> Thanks,
>>> Emilio

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