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From Evan Weaver <>
Subject Re: Fixing the data model names
Date Thu, 13 Aug 2009 04:23:34 GMT
Incidentally, is there any specific reason the collation has to be
pre-defined at the CF? What if any column could be an optional
supercolumn with a collation set at runtime? Then all CFs would be the


On Wed, Aug 12, 2009 at 10:02 PM, Jonathan Ellis<> wrote:
> If thrift were sane it would look something like
> struct Column {
>  byte[] name,
>  optional list<Column> subcolumns,
>  optional int64 timestamp,
>  optional byte[] value
> }
> "you can either have the subcolumns, or the timestamp and value" seems
> reasonable to me.
> of course in the real world, thrift can't do recursive structures, so
> we'd have to go with Column/SubColumn like SuperColumn/Column today.
> So... maybe not really an improvement after all. :)
> (Why am I not surprised to find out that protocol buffers does support
> this?  Sigh.)
> On Wed, Aug 12, 2009 at 8:51 PM, Evan Weaver<> wrote:
>> Hmm, my Ruby client internally refers to columns and subcolumns,
>> rather than supercolumns and columns...mainly because the subcolumn
>> position is optional, but the column_or_supercolumn position is not.
>> So there is something we agree on.
>> Do you think the lack of a timestamp in the supercolumn is confusing?
>> It's still not exactly a kind of column.
>> Evan
>> On Wed, Aug 12, 2009 at 9:47 PM, Jonathan Ellis<> wrote:
>>> I agree with the proposition that the SuperColumn name is weak.
>>> (Although not, as I mentioned, Column or ColumnFamily.)  And I could
>>> go with schema over keyspace.
>>> One option to deal with SC would be to excise the term SC (and SCF
>>> from the config) and instead just have Columns, which may or may not
>>> have SubColumns.  You would define this as
>>> <ColumnFamily withSubColumns="true" .../>
>>> "Insert a subcolumn named A into the Column named B" fits pretty well
>>> with how I think of things working.  And now you just have Rows and
>>> Columns!  Just like a RDB! :P
>>> -Jonathan
>>> On Wed, Aug 12, 2009 at 8:34 PM, Evan Weaver<> wrote:
>>>> Points taken, and I agree, except in my experience the current names
>>>> are not Pretty Good but rather Pretty Weird; the primary issues being
>>>> column family and super column.
>>>> If we go by the shorter-is-better principle, we might get:
>>>> Cluster
>>>> Schema
>>>> Row set
>>>> Row w/key
>>>> Field set
>>>> Field
>>>> "You take the user's key, and use that to insert into the Row Set
>>>> 'user_associations' at Field Set 'user_timeline,' a field named with a
>>>> time-based UUID representing now, and with a value of the new tweet's
>>>> key."
>>>> But let me study for a while and come up with a more researched proposal.
>>>> Evan
>>>> On Wed, Aug 12, 2009 at 9:21 PM, Jonathan Ellis<>
>>>>> On Wed, Aug 12, 2009 at 7:52 PM, Michael Koziarski<>
>>>>>> However I think it's worth considering this from a strategic
>>>>>> perspective, looking at how we want the project do grow and change,
>>>>>> rather than just as it is right now.  The key to successful adoption
>>>>>> is having a successful elevator pitch,  you can start using a database
>>>>>> without understanding relational-algebra because 'table' and 'column'
>>>>>> are such simple ways to reason about the tool.  As it stands
>>>>>> cassandra's takes a whiteboard and 15 minutes, before people get
>>>>>> you're talking about.
>>>>> If you want to explain it as "sort of like a relational db" then
>>>>> table -> CF
>>>>> column -> column
>>>>> key -> key
>>>>> row -> row
>>>>> That's the simple case, then all you have is "supercolumns can contain
>>>>> a list of simple columns."
>>>>> That really doesn't seem so hard to me.  I have explained this to *managers*.
>>>>>> Assuming the project gets anything like the adoption it deserves,
>>>>>> users we have today will be a *tiny minority* of the users we have
>>>>>> the future.  So imposing costs on the current userbase which will
>>>>>> huge benefits to future users, should be something we're willing
>>>>>> do.  In fact it's something that has been done repeatedly over the
>>>>>> last few weeks.
>>>>> I agree.  But as I said before I just don't see this as being an improvement.
>>>>>> Given those changes went in without debate, I'm not sure what the
>>>>>> reluctance is for making changes to the nomenclature for the project.
>>>>> As above.
>>>>>> Speaking as someone who's only been doing this a month, the naming
>>>>>> *still* confusing, and when I talk with people who wonder what
>>>>>> cassandra is all about I get blank looks when telling them what things
>>>>>> are called.  If you step back and want to tell someone how you'd
>>>>>> insert a tweet into someone's timeline using evan's weblog post:
>>>>>>  "You just take the user's key, and use that to insert into the
>>>>>> SuperColumnFamily 'UserAssociations' at SubColumn 'user_timeline',
>>>>>> ColumnName of a time based uuid representing now, and a value of
>>>>>> new tweet's key"
>>>>>> Column is in the name of 3 of the 5 concepts expressed, and in each
>>>>>> cases it's different.
>>>>> When you're inserting something nested 3 levels deep a certain amount
>>>>> of verbosity is unavoidable.  With Evan's nomenclature,
>>>>> "You take the user's record ID, and use that to insert into the Record
>>>>> Collection 'user associations' at Attribute Collection
>>>>> 'user_timeline,' an Attribute named with a time based uuid
>>>>> representing now, and with a value of the new tweet's key."
>>>>> I think that is a negative improvement.  Yay, now we are talking about
>>>>> Attribute Collections and Attributes instead of SuperColumns and
>>>>> Columns.  The same objections ("one object's name contains the
>>>>> other's!) apply, plus the new one of sounding so generic that it could
>>>>> apply to practically any system.
>>>>> -Jonathan
>>>> --
>>>> Evan Weaver
>> --
>> Evan Weaver

Evan Weaver

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