It's also introducing a suite of tools for monitoring and optimizing the performance of Cassandra clusters. Also read: Confluent makes Apache Kafka cloud-native. Constellation will, first and foremost, include Cassandra as a Service, featuring elastic scaling and consumption-based pricing.
Schumacher explained that the service will be based on Apache Cassandra but will include elements of the DataStax Enterprise DSE distribution, including certain security features; self-healing capabilities, like node sync and traffic control; as well as 2x-3x improved performance. The three sub-components will identify cluster and query issues and bottlenecks; Recommendation Insights will provide AI-driven recommendations to solve cluster issues.
Schumacher said that DataStax views the Cassandra market and ecosystem through a temporal lens, as a series of eras. First came the era of making Cassandra work with top-notch performance and functionality; next came the era of evangelizing Cassandra and expanding its popularity; following that came a focus on providing customer value through delivery of proprietary functionality in DSE.
That seems a direct response to first-party database services form the public cloud providers, which often provide Constellation-like deployment, scaling and pricing options by default. It accommodates numerous other APIs, works in a geographically distributed fashion by default and, in functionality announced two weeks ago at Microsoft's Build conference , integrates Apache Spark and Jupyter notebooks. Also read: Microsoft 'Builds' its data story, in the cloud and at the edge.
Maybe this competitive front is what inspired DataStax to point out to me that it believes Constellation's on-demand pricing to be 10 times less expensive Cosmos DB's.
While I'm never sure what it means to be a multiple less than something, it's clear that DataStax believes Constellation will be competitive on ease of deployment and ease of operation, while beating Cosmos DB on price. So while Cosmos DB offers numerous database APIs, exclusively on Microsoft Azure , Constellation will offer a single database that will eventually work across multiple public clouds. Specifically, DataStax says the service will launch on Google Cloud Platform in the fourth calendar quarter of this year, and that availability on Amazon Web Services and Azure will follow.
It will also offer an early access program this summer. Azure Data Lake Storage gets Okera security and governance platform support. And another one down: Logi Analytics acquires Zoomdata. Redis wants more than cache.
- A brief overview of the Cassandra storage engine?
- Cassandra Wilson.
- DataStax Constellation will deliver Apache Cassandra as a service | ZDNet.
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To do machine learning right, some take the approach of getting in the middle of a big problem and hoping to amass the data to train the network. That's the bet of startup Owlcam, whose The data that trains AI increasingly calls into question AI. Here you see the row being used as a Set, or more pedantically a Map, where Map's keys -- the cell names -- are the tags, and the values are empty. Instead of specifying cell name literals in our columnfamily definition, we just specify a comparator to tell Cassandra what type the names will be.
Finally, we want to allow users to group songs into playlists. The relational way to do this would be to create a playlists table with a foreign key to the songs, but as described above we're going to denormalize instead. The way we're going to do that is to pack each song in a playlist into one column, so fetching a playlist is just a single primary key lookup. Cassandra provides CompositeType for this. A playlist with the songs from earlier would then look like this -- one cell, or Map entry, per song, with the song's attributes packed into a composite name:.
A slice to Thrift means a set of columns from a single row, described either by name or as a contiguous run of columns from a starting point.
This last is useful for denormalized resultset columnfamilies like playlists since columns are always ordered by comparator. In our example, the only columnfamily with statically defined cell names is songs. We can fetch a given song as follows:. I'm simplifying here just a little by using human-readable forms for the row key and cell names; the actual Thrift API requires these be encoded as byte arrays.
To fetch the tags for a song, since we don't know what tag names might have been given we'll ask Cassandra to give us the entire row -- or rather, the first ten entries -- as represented by a SliceRange with empty start and finish:. CQL2 was introduced in Cassandra 0.
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- A primary key of a Materialized View can contain at most one other column;
However, CQL2 hewed extremely close to the concepts from thrift. Here are our column family definitions in CQL CQL2 makes some syntactic improvements over the cli above, notably around static column definitions. Interacting with the songs columnfamily will look familiar to SQL users:.
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Unfortunately that's about where the good news ends. Fundamentally CQL2 still forces us to deal with the raw storage engine representation of the data. You can see how cqlsh switches to a "tuple" format for wide rows that do not have cell names in common. We're going to have to skip actually inserting and reading playlists from CQL2 since cqlsh does not support interacting with CompositeType columns. We'll come back to this in the CQL3 section. CQL2 was easy to implement since it maps so straightforwardly to what the storage engine has been doing all along. But it turns out there are several major problems with this approach:.
Thus, we went back to the drawing board in Cassandra 1. CQL3 makes one very important changes to how it presents Cassandra data: wide rows are "transposed" and unpacked into named columns. From a relational standpoint, you can think of storage engine rows as partitions, within which object rows are clustered. For the song tags, we have two choices.
If we need to be compatible with data from an old-style schema, we can do that as follows:. Thus, we're giving the storage engine cell name, that we were using as a Map key, its own CQL3 column. The orange arrow shows how a single storage engine row becomes a CQL3 partition, with one CQL3 row per storage engine cell. The red arrow shows how the storage engine cell name is accessible in the tag column. If we simply use the old schema directly as-is, Cassandra will give cell names and values autogenerated CQL3 names: column1 , column2 , and so forth.
Here I'm accessing the data inserted earlier from CQL2, but with cqlsh --cql3 :. However, instead of creating a separate columnfamily to act as our tags set, CQL3 allows us to more naturally represent that sparse tag collection directly in the songs table, as a Set data type:. The red arrow shows how the cell name gets unpacked into three CQL3 columns. Presenting a storage engine row as a partition of multiple object rows solves all the problems we had with CQL2: clients do not have to know about the details of CompositeType packing, there is no distinction between "slice" syntax and normal WHERE predicates, and indexing wide rows becomes possible.
With the schema as given so far, this requires a sequential scan across the entire playlists dataset. There is no way to do this with the Thrift or CQL2 APIs -- not because we have chosen not to expose it there, but because there is no way to specify "the artist component of my CompositeType cell" in either index creation, or querying. We've seen here how CQL3 allows mapping Cassandra storage engine cells to a more powerful and more natural rows-and-columns representation.
In another post I'll explore in more detail some of the limitations of the one-cell-per-row design and how CQL3 improves on that limitation as well. Is the main difference in how the data is sorted or there are some other operational differences? Primary key fields cannot be updated directly. There is no need for secondary indices. With the thrift API, you can query arbitrary sublist from a wide row. How can you achieve the same with CQL3? Bluntly, that is a poor way to model things in any version of Cassandra.
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The rule of thumb is, use one columnfamily for each type of resultset you want to query. Cassandra is not Bigtable or HBase where you have to try to cram everything into very few ColumnFamilies because of implementation limitations. Thanks for your post. Here i am using DSE3. Here i want to create a column family having some unknown column.
At insertion of data one of the column-name should contain Dat-time of insert data and this column should contain rest all data. How should i configure above task. Please help me. I have badly need it. Thank you. I fail to see why it would not be included, but maybe you left it out for a reason? I received the following response:.
I am experiencing the same issue as Stefan and Leon. From my understanding it is not possible to create a secondary index on a field that is part of a composite primary key.