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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: is this correct, thrift unportable to CQL3Š.
Date Wed, 25 Sep 2013 08:39:30 GMT
> Nulls should definitely stay null (that's an old DB debate), but  if this
> is a generic case, we might consider adding an emptyValue() helper method.
> Would that be possible Sylvain?
>

As said previously, debating this is outside the scope of this mailing
list, but to make it short, using empty values for types that don't
naturally support them like Integer is going to be painful (inserting is
one thing, handling them on the read side is another) and confusing no
matter what. So you should avoid it in the first place (and there is *tons*
of way to do that) and consequently adding an helper to do something you
should avoid is a bad idea.

--
Sylvain



>
>
>> --
>> Sylvain
>>
>>
>>>
>>> Ie. This sounds like this solution would be perfect if we can get rid of
>>> the exception piece.
>>>
>>> Thanks much!!!
>>> Dean
>>>
>>> From: Sylvain Lebresne <sylvain@datastax.com<mailto:sylvain@datastax.com
>>> >>
>>> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>"
>>> <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
>>> Date: Tuesday, September 24, 2013 10:58 AM
>>> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <
>>> user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
>>> Subject: Re: is this correct, thrift unportable to CQL3Š.
>>>
>>> On Tue, Sep 24, 2013 at 6:17 PM, Vikas Goyal <vikas@easility.com<mailto:
>>> vikas@easility.com>> wrote:
>>> Ok. Great. It works for String and Decimal/Float but not for integer
>>> data type..
>>> i.e,, if I am passing "" to the composite key column which is either
>>> text or float, it works..
>>>
>>> session.execute(boundStatement.bind(rowkey, "", ByteBuffer.wrap(value)));
>>>
>>> But not working with bigint, int or varint..and getting following
>>> exception;
>>>
>>> Exception:Invalid type for value 1 of CQL type varint, expecting class
>>> java.math.BigInteger but class java.lang.String provided
>>>
>>> ..I am exploring more though..
>>>
>>> We're getting into details of the java driver at this point. For int,
>>> what you can do is:
>>>   boundStatement.setString("id", rowkey);
>>>   boundStatement.setBytesUnsafe("columnname", ByteBuffer.wrap(new
>>> byte[0]));
>>>   boundStatement.setBytes("columnvalue", ByteBuffer.wrap(value));
>>>
>>> In other words, the shorthand BoundStatement.bind() won't let you insert
>>> an empty value for types
>>> that don't naturally have an empty value (like int; keep in mind that an
>>> empty value is not the same
>>> than null). But you can circumvent that using setBytesUnsafe if you
>>> really want.
>>>
>>> Long story short, my advice would be to avoid using empty values for
>>> type that don't naturally have
>>> one (anything else than text and blob really). If you do, that's going
>>> to be painful (but possible) to
>>> work with, at least with the java driver (but for good reasons, java
>>> just doesn't have a good to
>>> represent an empty int value (again, you can have a null Integer but
>>> that's different)).
>>>
>>> --
>>> Sylvain
>>>
>>>
>>> Thanks a ton,
>>> Vikas Goyal
>>>
>>>
>>> On Tue, Sep 24, 2013 at 9:05 PM, Sylvain Lebresne <sylvain@datastax.com
>>> <mailto:sylvain@datastax.com>> wrote:
>>>
>>> However,we tried missing the value but it didn't work :(
>>>
>>> Right, because not providing a value is akin to having a null value (in
>>> the CQL3 sense of the term, which is different from what Dean asked about)
>>> and null values are not allowed for primary key columns.
>>> You could however insert an *empty* value if you wanted, which in you
>>> case is just inserting an empty string since colname is a string. Thrift
>>> doesn't allow more or less in that case.
>>>
>>> --
>>> Sylvain
>>>
>>>
>>>
>>> So our code is like below where we are using 3 values if colname is not
>>> null..else 2 values..
>>>
>>>             if (key != null) {
>>>                 PreparedStatement statement = session.prepare("INSERT
>>> INTO keys.StringIndice (id, colname, colvalue) VALUES (?, ?, ?)");
>>>                 BoundStatement boundStatement = new
>>> BoundStatement(statement);
>>>
>>> session.execute(boundStatement.bind(StandardConverters.convertFromBytes(String.class,
>>> rowKey), key, ByteBuffer.wrap(value)));
>>>             } else {
>>>                 PreparedStatement statement = session.prepare("INSERT
>>> INTO " + keys + "." + table + "(id, colvalue) VALUES (?, ?)");
>>>                 BoundStatement boundStatement = new
>>> BoundStatement(statement);
>>>
>>> session.execute(boundStatement.bind(StandardConverters.convertFromBytes(String.class,
>>> rowKey), ByteBuffer.wrap(value)));
>>>           }
>>>
>>> And, I did that and getting this exception:
>>>
>>> Exception:Missing PRIMARY KEY part colname since colvalue is set
>>>
>>> And just FYI. Our Column Family definition is below:
>>>
>>> CREATE TABLE keys.StringIndice (id text,
>>> colname text,
>>> colvalue blob,
>>> PRIMARY KEY (id,colname, colvalue)) WITH COMPACT STORAGE)
>>>
>>> Thanks again,
>>> Vikas Goyal
>>>
>>>
>>>
>>> On Tue, Sep 24, 2013 at 7:02 PM, Sylvain Lebresne <sylvain@datastax.com
>>> <mailto:sylvain@datastax.com>> wrote:
>>> Short answer: not, this is not correct.
>>>
>>> Longer answer: what you call "null" is actually an empty value (which is
>>> *not* the same thing, unless you consider an empty string is the same thing
>>> than a null string). As it happens, C* always an empty value as a valid
>>> value for any type and that's true of both thrift and CQL3. What is true is
>>> that CQL3 discourage the use of empty values for type for which it doesn't
>>> particularly make sense (integers typically) by not having a particular
>>> easy to use syntax to input them. But that's supported nonetheless. If you
>>> use a prepared statement for instance (where you send values already
>>> serialized), nothing will prevent you from sending an empty value. Even if
>>> you don't want to use a prepared statement, CQL3 has conversion functions (
>>> http://cassandra.apache.org/doc/cql3/CQL.html#blobFun) that allows to
>>> do it (for instance, "blobAsInt(0x)" will be an empty int value).
>>>
>>> --
>>> Sylvain
>>>
>>>
>>>
>>> On Tue, Sep 24, 2013 at 2:36 PM, Hiller, Dean <Dean.Hiller@nrel.gov
>>> <mailto:Dean.Hiller@nrel.gov>> wrote:
>>> Many applications in thrift use the wide row with composite column name
>>> and as an example, let's say golf score for instance and we end up with
>>> golf score : pk like so
>>>
>>> null : pk56
>>> null : pk45
>>> 89 : pk90
>>> 89: pk87
>>> 90: pk101
>>> 95: pk17
>>>
>>> Notice that there are some who do not have a golf score(zero would not
>>> quite make sense and would be interpreted as a golf score).  I am hearing
>>> from this post if they are correct that this is not portable to CQL3???  Is
>>> this true?
>>> http://stackoverflow.com/questions/18963248/how-can-i-have-null-column-value-for-a-composite-key-column-in-cql3
>>>
>>> (This sounds like a major deficit to me as the wide row now can only be
>>> used where actual values exist?????).  Is it possible to port this pattern
>>> to CQL3?
>>>
>>> Thanks,
>>> Dean
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
>
> --
>
> :- a)
>
>
> Alex Popescu
> Sen. Product Manager @ DataStax
> @al3xandru
>

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