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Accumulo >> mail # dev >> Quoted visibility equality?


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Ed Kohlwey 2013-07-13, 23:32
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Eric Newton 2013-07-15, 13:34
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Keith Turner 2013-07-15, 13:23
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Ed Kohlwey 2013-07-15, 17:47
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Re: Quoted visibility equality?
Quotes in the underlying bytes in the column visibility will get
stripped during evaluation. They are only used for parsing the
expression, not for comparing with authorizations.

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Christopher L Tubbs II
http://gravatar.com/ctubbsii
On Mon, Jul 15, 2013 at 1:47 PM, Ed Kohlwey <[EMAIL PROTECTED]> wrote:
> My intention was for the strings to be interpreted as java code - so the
> quotes are not part of the authorization name. The labels would be a&b and
> "a"&b (if we're talking bare strings).
>
> The issue I'm really trying to get at is that a programmer would think of
> these two labels as equivalent. This is a natural assumption for a
> programmer who generally thinks that escape characters or quotes don't
> contribute to the meaning of an expression because thats how programming
> languages usually work. But it sounds like thats not the case.
>
>
> On Mon, Jul 15, 2013 at 9:23 AM, Keith Turner <[EMAIL PROTECTED]> wrote:
>
>> On Sat, Jul 13, 2013 at 7:32 PM, Ed Kohlwey <[EMAIL PROTECTED]> wrote:
>>
>> > I just noticed something as I was hacking today on the trunk - does the
>> new
>> > column visibility code (with escape sequences) accommodate visibilities
>> > that are equivalent but not stored using the same byte representation? My
>> > assumption is no...
>> >
>> > Ie., is the visibility "a&b" equivalent to "\"a\"&b" for the purpose of
>> the
>> > max versions iterator, etc.?
>> >
>>
>>
>> I do not think the visibility "a&b" and  "\"a\"&b" are equivalent.   The
>> escaped quotes are not ignored, they are part of the label.  To
>> see  "\"a\"&b", you would need to pass an authorization of: "a"&b to the
>> scanner.   Passing an authorization of a&b to scan would not see a column
>> labeled with "\"a\"&b".
>>
>> The exact bytes you pass to ColumnVis is whats stored.  The colvis bytes
>> are used for lexicographic sorting w/o interpreting their contents.
>>  So "a&b" and "\"a\"&b"  would sort to different places.
>>
>> If you did store something thats logically equivalent like a&b and b&a,
>> then these would still sort to different places.    ColumnVisibility has a
>> flatten() function that may help in some cases, but it will not always
>> normalize two expressions that are logically equivalent to the exact same
>> expression.
>>
>> Keith
>>
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Ed Kohlwey 2013-07-15, 19:46
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Christopher 2013-07-15, 19:56