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Date: Tue, 10 Jul 2012 16:34:40 +0200
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Subject: Re: Dynamic CF
From: Sylvain Lebresne <sylvain@datastax.com>
To: user@cassandra.apache.org
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On Tue, Jul 10, 2012 at 4:19 PM, Carlos Carrasco <
carlos.carrasco@groupalia.com> wrote:

> I think he means something like having a fixed set of coiumns in the table
> definition, then in the actual rows having other columns not specified in
> the defintion, indepentent of the composited part of the PK. When I
> reviewed CQL3 for using in Gossie[1] I realized I couldn't have this, and
> that it would complicate things like migrations or optional columns. For
> this reason I didn't use CQL3 and instead wrote a row unmaper that detects
> the discontinuities in the composited part and uses those as the boundaries
> for the individual concrete rows stored in a wide row [2]. For example:
>
> Given a Timeline table defined as key validation UTF8Type, column name
> validation CompositeType(LongType, AsciiType), value validation BytesType:
>
> Timeline: {
>     user1: {
>         1341933021000000: {
>             Author: "Tom",
>             Body: "Hey!"
>         },
>         1341933022000000: {
>             Author: "Paul",
>             Body: "Nice",
>             Lat: 40.0,
>             Lon: 20.0
>         },
>         1341933023000000: {
>             Author: "Lana",
>             Body: "Cool"
>         }
>     },
>     ...
> }
>
> Both of the following structs are valid and will be able to be unmaped
> from the wide row "user1":
>
> type Tweet struct {
>     UserID  string `cf:"Timeline" key:"UserID" cols:"When"`
>     When    int64
>     Author  string
>     Body    string
> }
>
> type GeoTweet struct {
>     UserID  string `cf:"Timeline" key:"UserID" cols:"When"`
>     When    int64
>     Author  string
>     Body    string
>     Lat     float32
>     Lon     float32
> }
>

That's exactly how CQL3 works. In that example, you would declare:
CREATE TABLE tweet (
    UserID text,
    When int,
    Author text,
    Body text,
    Lat float,
    Long float,
    PRIMARY KEY (UserId, When)
)
and that would layout things *exactly* like your Timeline above, but with
validation.

The fact that you have to declare Lat and Long does not mean that every CQL
row must have them.


> much nicer behaviour for model changes and migrations.
>

Not sure what you mean by that since adding new columns to a CQL3
definition is basically free.

--
Sylvain

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On Tue, Jul 10, 2012 at 4:19 PM, Carlos Carrasco <span dir=3D"ltr">&lt;<a h=
ref=3D"mailto:carlos.carrasco@groupalia.com" target=3D"_blank">carlos.carra=
sco@groupalia.com</a>&gt;</span> wrote:<br><div class=3D"gmail_quote"><bloc=
kquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #cc=
c solid;padding-left:1ex">
I think he means something like having a fixed set of coiumns in the table =
definition, then in the actual rows having other columns not specified in t=
he defintion, indepentent of the composited part of the PK. When I reviewed=
 CQL3 for using in Gossie[1] I realized I couldn&#39;t have this, and that =
it would complicate things like migrations or optional columns. For this re=
ason I didn&#39;t use CQL3 and instead wrote a row unmaper that detects the=
 discontinuities in the composited part and uses those as the boundaries fo=
r the individual concrete rows stored in a wide row [2]. For example:<div>

<br></div><div><div>Given a Timeline table defined as key validation UTF8Ty=
pe, column name validation CompositeType(LongType, AsciiType), value valida=
tion BytesType:</div><div><br></div><div>Timeline: {</div><div>=A0 =A0 user=
1: {</div>

<div>=A0 =A0 =A0 =A0 1341933021000000: {</div><div>=A0 =A0 =A0 =A0 =A0 =A0 =
Author: &quot;Tom&quot;,</div><div>=A0 =A0 =A0 =A0 =A0 =A0 Body: &quot;Hey!=
&quot;</div><div>=A0 =A0 =A0 =A0 },</div><div>=A0 =A0 =A0 =A0 1341933022000=
000: {</div><div>=A0 =A0 =A0 =A0 =A0 =A0 Author: &quot;Paul&quot;,</div>

<div>=A0 =A0 =A0 =A0 =A0 =A0 Body: &quot;Nice&quot;,</div><div>=A0 =A0 =A0 =
=A0 =A0 =A0 Lat: 40.0,</div><div>=A0 =A0 =A0 =A0 =A0 =A0 Lon: 20.0</div><di=
v>=A0 =A0 =A0 =A0 },</div><div>=A0 =A0 =A0 =A0 1341933023000000: {</div><di=
v>=A0 =A0 =A0 =A0 =A0 =A0 Author: &quot;Lana&quot;,</div><div>

=A0 =A0 =A0 =A0 =A0 =A0 Body: &quot;Cool&quot;</div><div>=A0 =A0 =A0 =A0 }<=
/div><div>=A0 =A0 },</div><div>=A0 =A0 ...</div><div>}</div><div><br></div>=
<div>Both of the following structs are valid and will be able to be unmaped=
 from the wide row &quot;user1&quot;:</div>

<div><br></div><div>type Tweet struct {</div><div>=A0 =A0 UserID =A0string =
`cf:&quot;Timeline&quot; key:&quot;UserID&quot; cols:&quot;When&quot;`</div=
><div>=A0 =A0 When =A0 =A0int64</div><div>=A0 =A0 Author =A0string</div><di=
v>=A0 =A0 Body =A0 =A0string</div>

<div>}</div><div><br></div><div>type GeoTweet struct {</div><div>=A0 =A0 Us=
erID =A0string `cf:&quot;Timeline&quot; key:&quot;UserID&quot; cols:&quot;W=
hen&quot;`</div><div>=A0 =A0 When =A0 =A0int64</div><div>=A0 =A0 Author =A0=
string</div><div>

=A0 =A0 Body =A0 =A0string</div><div>=A0 =A0 Lat =A0 =A0 float32</div><div>=
=A0 =A0 Lon =A0 =A0 float32</div><div>}</div></div></blockquote><div><br></=
div><div>That&#39;s exactly how CQL3 works. In that example, you would decl=
are:</div><div>CREATE TABLE tweet (</div>
<div>=A0 =A0 UserID text,</div><div>=A0 =A0 When int,</div><div>=A0 =A0 Aut=
hor text,</div><div>=A0 =A0 Body text,</div><div>=A0 =A0 Lat float,</div><d=
iv>=A0 =A0 Long float,</div><div>=A0 =A0 PRIMARY KEY (UserId, When)</div><d=
iv>)</div><div>and that would layout things *exactly* like your Timeline ab=
ove, but with validation.</div>
<div><br></div><div>The fact that you have to declare Lat and Long does not=
 mean that every CQL row must have them.</div><div>=A0</div><blockquote cla=
ss=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;pa=
dding-left:1ex">
<div>much nicer behaviour for model changes and migrations.</div></blockquo=
te><div><br></div><div>Not sure what you mean by that since adding new colu=
mns to a CQL3 definition is basically free.</div><div><br></div><div>--</di=
v>
<div>Sylvain</div></div>

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