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From Peter Lin <wool...@gmail.com>
Subject Re: Performance problem with large wide row inserts using CQL
Date Thu, 20 Feb 2014 20:26:11 GMT
Hi Duyhai,

yes, I am talking about mixing static and dynamic columns in a single
column family. Let me give you an example from retail.

Say you're amazon and you sell over 10K different products. How do you
store all those products with all the different properties like color,
size, dimensions, etc. With relational databases people use EAV (entity
attribute value) tables. This means querying for data the system has to
reconstruct the object by pivot a bunch of rows and flattening it out to
populate the java object. Typically there are common fields to a product
like SKU, price, and category.

Using both static and dynamic columns, data can be stored in 1 row and
queried by 1 row. Anyone that has used EAV approach to build product
databases will tell you how much that sucks. Another example is from auto
insurance. Typically a policy database will allow 1 or more types of items
for property insurance. Property insurance is home/auto insurance.

Each insurance carrier supports different number of insurable items,
coverages and endorsements. Many systems use the same EAV approach, but the
problem is bigger. Typically a commercial auto policy may have hundreds of
drivers and vehicles. Each policy may have dozens or hundreds of coverages
and endorsements. It is common for an auto insurance model to have hundreds
of coverage and endorsements with different properties. Using the old ORM
approach, it's usually mapped table-per-class. Problem is, that results in
query explosion for polymorphic queries. This is a known problem with
polymorphic queries using traditional techniques.

Given that Cassandra + thrift gives developers the ability to store dynamic
columns of different types, it solves the performance issues inherent in
EAV technique.

The point I was trying to make in my first response is that going with pure
CQL makes it much harder to take advantage of the COOL features of
Cassandra. It does require building a framework to make it "mostly"
transparent to developers, but it is worth it in my opinion to learn and
understand both thrift and cql. I use annotations in my framework and
delegates to handle the serialization. This way, the developer only needs
annotate the class and the framework handles serialization and
deserialization.





On Thu, Feb 20, 2014 at 3:05 PM, DuyHai Doan <doanduyhai@gmail.com> wrote:

> "Developers can use what ever type they want for the name or value in a
> dynamic column and the framework will handle it appropriately."
>
>  What do you mean by "dynamic" column ? If you want to be able to insert
> an arbitrary number of columns in one physical row, CQL3 clustering is
> there and does pretty well the job.
>
>  If by "dynamic" you mean a column whose validation type can change at
> runtime (like the dynamic composite type :
> http://hector-client.github.io/hector/build/html/content/composite_with_templates.html)
> then why don't you just use blob type and serialize it yourself at client
> side ?
>
>  More pratically, in your previous example :
>
>   - insert into myColumnFamily(staticColumn1, staticColumn2, 20 as int,
> dynamicColumn as string) into ('text1','text2',30.55 as double, 3500 as
> long)
>
>  I can't see real sensible use-case where you need to mix static and
> dynamic columns in the same column family. If you need to save domain
> model, use skinny row with a fixed number of columns known before hand. If
> you want to store time series or timeline of data, wide row is there.
>
>
> On Thu, Feb 20, 2014 at 8:55 PM, Peter Lin <woolfel@gmail.com> wrote:
>
>>
>> my apologies Sylvain, I didn't mean to misquote you. I still feel that
>> even if someone is only going to use CQL, it is "worth it" to learn thrift.
>>
>> In the interest of discussion, I looked at both jira tickets and I don't
>> see how that makes it so a developer can specify the name and value type
>> for a dynamic column.
>>
>> https://issues.apache.org/jira/browse/CASSANDRA-6561
>> https://issues.apache.org/jira/browse/CASSANDRA-4851
>>
>> Am I missing something? If the grammar for insert statements doesn't give
>> users the ability declare the name and value type, it means the developer
>> has to default name and value to bytes. In their code, they have to handle
>> that manually or build their own framework. I built my own framework, which
>> handles this for me. Developers can use what ever type they want for the
>> name or value in a dynamic column and the framework will handle it
>> appropriately.
>>
>> To me, developers should take time to learn both and use both. I realize
>> it's more work to understand both and take time to read the code. Not
>> everyone is crazy enough spend time reading cassandra code base or spend
>> hundreds of hours studying hector and other cassandra clients. I will say
>> this, if I hadn't spend time studying cassandra and reading Hector code, I
>> wouldn't have been able to help one of DataStax customer port Hector to
>> .Net. I also wouldn't have been able to port Hector to C# natively in 3
>> months.
>>
>> Rather than recommend people be lazy, it would be more useful to list the
>> pros/cons. To my knowledge, there isn't a good writeup on the pros/cons of
>> thrift and cql on cassandra.apache.org. I don't know if the DataStax
>> docs have a detailed write up of it, does it?
>>
>>
>>
>>
>> On Thu, Feb 20, 2014 at 12:46 PM, Sylvain Lebresne <sylvain@datastax.com>wrote:
>>
>>> On Thu, Feb 20, 2014 at 6:26 PM, Peter Lin <woolfel@gmail.com> wrote:
>>>
>>>>
>>>> I disagree with the sentiment that "thrift is not worth the trouble".
>>>>
>>>
>>> Way to quote only part of my sentence and get mental on it. My full
>>> sentence was "it's probably not worth the trouble to start with thrift if
>>> you're gonna use CQL later".
>>>
>>>
>>>>
>>>> CQL and all SQL inspired dialects limit one's ability to use arbitrary
>>>> typed data in dynamic columns. With thrift it's easy and straight forward.
>>>> With CQL there is no way to tell Cassandra the type of the name and value
>>>> for a dynamic column. You can only set the default type. That means using
a
>>>> "pure cql" approach you can deviate from the default type. Cassandra will
>>>> throw an exception indicating the type is different than the default type.
>>>>
>>>
>>>> Until such time that CQL abandons the shackles of SQL and adds the
>>>> ability to indicate the column and value type. Something like this
>>>>
>>>
>>>> insert into myColumnFamily(staticColumn1, staticColumn2, 20 as int,
>>>> dynamicColumn as string) into ('text1','text2',30.55 as double, 3500 as
>>>> long)
>>>>
>>>> This is one area where Thrift is superior to CQL. Having said that,
>>>> it's valid to use Cassandra "as if" it was a relational database, but then
>>>> you'd miss out on some of the unique features.
>>>>
>>>
>>> Man, if I had a nickel every time someone came on that mailing list
>>> pretending that something was possible with thrift and not CQL ... I will
>>> claim this: with CASSANDRA-6561 and CASSANDRA-4851 that just got in, there
>>> is *nothing* that thrift can do that CQL cannot. But well, what do I know
>>> about Cassandra.
>>>
>>> --
>>> Sylvain
>>>
>>>
>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Thu, Feb 20, 2014 at 12:12 PM, Sylvain Lebresne <
>>>> sylvain@datastax.com> wrote:
>>>>
>>>>> On Thu, Feb 20, 2014 at 2:16 PM, Edward Capriolo <
>>>>> edlinuxguru@gmail.com> wrote:
>>>>>
>>>>>> For what it is worth you schema is simple and uses compact storage.
>>>>>> Thus you really dont need anything in cassandra 2.0 as far as i can
tell.
>>>>>> You might be happier with a stable release like 1.2.something and
just
>>>>>> hector or astyanax. You are really dealing with many issues you should
not
>>>>>> have to just to protoype a simple cassandra app.
>>>>>
>>>>>
>>>>>
>>>>> Of course, if everyone was using that reasoning, no-one would ever
>>>>> test new features and report problems/suggest improvement. So thanks
to
>>>>> anyone like Rüdiger that actually tries stuff and take the time to report
>>>>> problems when they think they encounter one. Keep at it, *you* are the
one
>>>>> helping Cassandra to get better everyday.
>>>>>
>>>>> And you are also right Rüdiger that it's probably not worth the
>>>>> trouble to start with thrift if you're gonna use CQL later. And you
>>>>> definitively should use CQL, it is Cassandra's future.
>>>>>
>>>>> --
>>>>> Sylvain
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> On Thursday, February 20, 2014, Sylvain Lebresne <
>>>>>> sylvain@datastax.com> wrote:
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > On Wed, Feb 19, 2014 at 9:38 PM, Rüdiger Klaehn <rklaehn@gmail.com>
>>>>>> wrote:
>>>>>> >>
>>>>>> >> I have cloned the cassandra repo, applied the patch, and
built it.
>>>>>> But when I want to run the bechmark I get an exception. See below.
I tried
>>>>>> with a non-managed dependency to
>>>>>> cassandra-driver-core-2.0.0-rc3-SNAPSHOT-jar-with-dependencies.jar,
which I
>>>>>> compiled from source because I read that that might help. But that
did not
>>>>>> make a difference.
>>>>>> >>
>>>>>> >> So currently I don't know how to give the patch a try. Any
ideas?
>>>>>> >>
>>>>>> >> cheers,
>>>>>> >>
>>>>>> >> Rüdiger
>>>>>> >>
>>>>>> >> Exception in thread "main" java.lang.IllegalArgumentException:
>>>>>> replicate_on_write is not a column defined in this metadata
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ColumnDefinitions.getAllIdx(ColumnDefinitions.java:273)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ColumnDefinitions.getFirstIdx(ColumnDefinitions.java:279)
>>>>>> >>     at com.datastax.driver.core.Row.getBool(Row.java:117)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.TableMetadata$Options.<init>(TableMetadata.java:474)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.TableMetadata.build(TableMetadata.java:107)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.Metadata.buildTableMetadata(Metadata.java:128)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.Metadata.rebuildSchema(Metadata.java:89)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ControlConnection.refreshSchema(ControlConnection.java:259)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ControlConnection.tryConnect(ControlConnection.java:214)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ControlConnection.reconnectInternal(ControlConnection.java:161)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.ControlConnection.connect(ControlConnection.java:77)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.Cluster$Manager.init(Cluster.java:890)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.Cluster$Manager.newSession(Cluster.java:910)
>>>>>> >>     at
>>>>>> com.datastax.driver.core.Cluster$Manager.access$200(Cluster.java:806)
>>>>>> >>     at com.datastax.driver.core.Cluster.connect(Cluster.java:158)
>>>>>> >>     at
>>>>>> cassandra.CassandraTestMinimized$delayedInit$body.apply(CassandraTestMinimized.scala:31)
>>>>>> >>     at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
>>>>>> >>     at
>>>>>> scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
>>>>>> >>     at scala.App$$anonfun$main$1.apply(App.scala:71)
>>>>>> >>     at scala.App$$anonfun$main$1.apply(App.scala:71)
>>>>>> >>     at scala.collection.immutable.List.foreach(List.scala:318)
>>>>>> >>     at
>>>>>> scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
>>>>>> >>     at scala.App$class.main(App.scala:71)
>>>>>> >>     at
>>>>>> cassandra.CassandraTestMinimized$.main(CassandraTestMinimized.scala:5)
>>>>>> >>     at
>>>>>> cassandra.CassandraTestMinimized.main(CassandraTestMinimized.scala)
>>>>>> >
>>>>>> > I believe you've tried the cassandra trunk branch? trunk is
>>>>>> basically the future Cassandra 2.1 and the driver is currently unhappy
>>>>>> because the replicate_on_write option has been removed in that version.
I'm
>>>>>> supposed to have fixed that on the driver 2.0 branch like 2 days
ago so
>>>>>> maybe you're also using a slightly old version of the driver sources
in
>>>>>> there? Or maybe I've screwed up my fix, I'll double check. But anyway,
it
>>>>>> would be overall simpler to test with the cassandra-2.0 branch of
>>>>>> Cassandra, with which you shouldn't run into that.
>>>>>> > --
>>>>>> > Sylvain
>>>>>>
>>>>>> --
>>>>>> Sorry this was sent from mobile. Will do less grammar and spell check
>>>>>> than usual.
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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