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From I PVP <i...@hotmail.com>
Subject Re: Modeling contact list, plain table or List<UDT>
Date Mon, 11 Jan 2016 20:41:03 GMT
The below table and materialized view will solve the SELECT requirements of my current application
.
The challenge now is when the user decides to DELETE one specific contact from his contact
list. I could add the objectid to a composite partition key together with the userid. But
that would make the SELECT inviable.

 Any ideas/suggestions?


CREATE TABLE communication.user_contact (
userid int,
contactname text,
contactid int,
createdat timeuuid,
favoriteat timestamp,
isfavorite boolean,
objectid timeuuid,
PRIMARY KEY (userid, contactname)
) WITH CLUSTERING ORDER BY ( contactname DESC )


CREATE MATERIALIZED VIEW communication.user_contact_by_favorite AS
SELECT userid, isfavorite, contactname, contactid, createdat, favoriteat, objectid
FROM user_contact
WHERE userid IS NOT NULL AND isfavorite IS NOT NULL AND contactname IS NOT NULL
PRIMARY KEY ( ( userid, isfavorite ), contactname )
WITH CLUSTERING ORDER BY ( contactname DESC )

Thanks

--
IPVP


From: DuyHai Doan <doanduyhai@gmail.com><mailto:doanduyhai@gmail.com>
Reply: user@cassandra.apache.org <user@cassandra.apache.org>><mailto:user@cassandra.apache.org>
Date: January 11, 2016 at 11:14:10 AM
To: user@cassandra.apache.org <user@cassandra.apache.org>><mailto:user@cassandra.apache.org>
Subject:  Re: Modeling contact list, plain table or List

In the current iteration of materialized view, it is still not possible to have WHERE clause
other than IS NOT NULL so is_favourite IS TRUE won't work.

Still there is a JIRA created to support this feature : https://issues.apache.org/jira/browse/CASSANDRA-10368

About cardinality of favorite vs non-favorites, it doesn't matter in [https://ssl.gstatic.com/ui/v1/icons/mail/images/cleardot.gif]
this case because the OP said "Less then one hundred contacts by user is the normal."

So even if all contacts are stuck in one unique favorite state, the materialized view partition
for one user is at most 100. Even for extreme edge case with users having 10 000 contacts,
it's still a manageable partition size for C*.

But I agree it is important to know before-hand the favorite/non-favorite update frequency
since it will impact the write throughput on the MV.

For more details on materialized view impl and performance: http://www.doanduyhai.com/blog/?p=1930

On Mon, Jan 11, 2016 at 1:36 PM, Jack Krupansky <jack.krupansky@gmail.com<mailto:jack.krupansky@gmail.com>>
wrote:
The new Materialized View feature is just an automated way of creating and maintaining what
people used to call a "query table", which is the traditional Cassandra data modeling technique
for performing queries on on than the primary key for a table - you store the same columns
in different tables using different columns for the primary key.

One also needs to be careful to include all columns of the original primary key in each MV
primary key - in addition to whatever column(s) are to be used for indexing in each MV (so
that Cassandra can find the old row when it needs to update the MV when the base table row
changes, such as on a deletion.)

But before creating MVs, you first need to answer questions about how the app needs to query
the data. Even with MV, conceptualizing queries needs to precede data modeling.

For example, what is the cardinality of favorites vs. non-favorites, does the app even need
to query by favorates, as opposed to querying all contacts and retrieving is_favorite as simply
a non-key column value, whether favorites need to be retrieved separately from non-favorites,
the frequency and latency requirements for query by favorite status, etc. Once these questions
are answered, decisions can be made about data modeling.

-- Jack Krupansky

On Mon, Jan 11, 2016 at 5:13 AM, Carlos Alonso <info@mrcalonso.com<mailto:info@mrcalonso.com>>
wrote:
I have never used Materialized Views so maybe this suggestion is not possible, but in this
case, wouldn't it make sense to define the materialized view as

is_favourite IS TRUE
instead of
is_favourite IS NOT NULL?

Carlos Alonso | Software Engineer | @calonso<https://twitter.com/calonso>

On 10 January 2016 at 09:59, DuyHai Doan <doanduyhai@gmail.com<mailto:doanduyhai@gmail.com>>
wrote:
Try this

CREATE TABLE communication.user_contact_list (
  user_id uuid,
  contact_id uuid,
  contact_name text,
  created_at timeuuid,
  is_favorite boolean,
  favorite_at timestamp,
  PRIMARY KEY (user_id, contact_name, contact_id)
);

CREATE MATERIALIZED VIEW communication.user_favorite_contact_list
AS SELECT * FROM communication.user_contact_list
WHERE user_id IS NOT NULL AND contact_name IS NOT NULL
AND contact_id IS NOT NULL AND is_favorite IS NOT NULL
PRIMARY KEY(user_id, is_favorite, contact_name, contact_id)

If the flag is_favorite is not updated very often the write perf hit due to materialized view
is acceptable.

On Sat, Jan 9, 2016 at 11:57 PM, Isaac P. <ipvp@hotmail.com<mailto:ipvp@hotmail.com>>
wrote:
Jack/ Michael,

Thanks for answering.

How big?: Less then one hundred contacts by user is the normal.

Update requirements: The UPDATE requirements are all around  each user “favoriting/unfavoriting”
the contacts . Deleting is not very frequent.

Does that mean that in C* 3.02 , for this use case to work, the contact name  must be part
of a  composite partition key in order to allow sorting by contact_name like this ? :

CREATE TABLE communication.user_contact_list (
user_id uuid,
contact_name text,
is_favorite boolean,
contact_id uuid,
created_at timeuuid,
favorite_at timestamp,
PRIMARY KEY ((user_id, contact_name), is_favorite)
)  WITH CLUSTERING ORDER BY (contact_name ASC);

Query: Select * from user_contact_list where user_id = :userid and is_favorite = true order
by contact_name asc;

Looks like each contact as a row/clustering key will be the way to go.

Thanks

IPVP


From: Laing, Michael <michael.laing@nytimes.com><mailto:michael.laing@nytimes.com>
Reply: user@cassandra.apache.org<mailto:user@cassandra.apache.org> <user@cassandra.apache.org>><mailto:user@cassandra.apache.org>
Date: January 9, 2016 at 11:51:27 AM
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org> <user@cassandra.apache.org>><mailto:user@cassandra.apache.org>
Subject:  Re: Modeling contact list, plain table or List


Note that in C* 3.02 the second query is invalid:

cqlsh> Select * from communication.user_contact_list where user_id = 98f50f00-b6d5-11e5-afec-6003089bf572
and is_favorite = true order by contact_name asc;

InvalidRequest: code=2200 [Invalid query] message="PRIMARY KEY column "is_favorite" cannot
be restricted as preceding column "contact_name" is not restricted"

On Fri, Jan 8, 2016 at 6:50 PM, Jack Krupansky <jack.krupansky@gmail.com<mailto:jack.krupansky@gmail.com>>
wrote:
How big is each contact list expected to be? Dozens? Hundreds? Thousands? If just dozens,
a simple list column would seem sufficient. If thousands, the row (not partition) would get
kind of bloated.

What requirements do you have for updating? If updating contacts and lots of contacts, I think
I'd prefer each contact as a row/clustering key. Nice to be able to do selective queries to
return slices of the clustering key values, which is not so easy if they are all just a single
list column.

-- Jack Krupansky

On Fri, Jan 8, 2016 at 6:31 PM, Isaac P. <ipvp@hotmail.com<mailto:ipvp@hotmail.com>>
wrote:
Hi everyone

What would perform better while modeling a simple user contact list  that will be used mainly
to select the recipients for/from/to messages ?

a) Individual rows to each (user, contact) pair so a select would fetch all the rows  to retrieve
all the contacts from a given user.

or

b) A single row for each user containing the List<Contact>  UDT.

Aside of the basic CRUD, the queries will be the following ones:

Select * from user_contact_list where user_id = :userid order by contact_name asc

Select * from user_contact_list where user_id = :userid and is_favorite = true order by contact_name
asc

After reading this https://docs.datastax.com/en/cql/3.0/cql/ddl/ddl_compound_keys_c.html 
the table is looking like this:

CREATE TABLE communication.user_contact_list (
user_id uuid,
contact_id uuid,
contact_name text,
created_at timeuuid,
is_favorite boolean,
favorite_at timestamp,
PRIMARY KEY (user_id, contact_name, is_favorite)
);

Any guidance will be appreciated.

Thanks

--
IPVP







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