Cassandra使用入门

jieforest

Next, add some data to the CarDataStore keyspace like so:

1. [default@unknown] use CarDataStore;
   
2. Authenticated to keyspace: CarDataStore
   
3. [default@CarDataStore] set Cars['Prius']['make'] = 'toyota';
   
4. Value inserted.
   
5. [default@CarDataStore] set Cars['Prius']['model'] = 'prius 3';
   
6. Value inserted.
   
7. [default@CarDataStore] set Cars['Corolla']['make'] = 'toyota';
   
8. Value inserted.
   
9. [default@CarDataStore] set Cars['Corolla']['model'] = 'le';
   
10. Value inserted.
    
11. [default@CarDataStore] set Cars['fit']['make'] = 'honda';
    
12. Value inserted.
    
13. [default@CarDataStore] set Cars['fit']['model'] = 'fit sport';
    
14. Value inserted.
    
15. [default@CarDataStore] set Cars['focus']['make'] = 'ford';
    
16. Value inserted.
    
17. [default@CarDataStore] set Cars['focus']['model'] = 'sel';
    
18. Value inserted.

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The set of commands illustrated is a way to add data to Cassandra. Using this command, a name-value pair or column value is added within a row, which in turn is defined in a ColumnFamily in a keyspace. For example, set Cars['Prius']['make'] = 'toyota', a name-value pair: 'make' = 'toyota' is added to a row, which is identified by the key 'Prius'. The row identified by 'Prius' is part of the Cars ColumnFamily. The Cars ColumnFamily is defined within the CarDataStore, which you know is a keyspace.

jieforest

Once the data is added, you can query and retrieve it. To get the name-value pairs or column names and values for a row identified by Prius, use the following command: get Cars['Prius']. The output should be like so:

1. [default@CarDataStore] get Cars['Prius'];
   
2. => (column=make, value=746f796f7461, timestamp=1301824068109000)
   
3. => (column=model, value=70726975732033, timestamp=1301824129807000)
   
4. Returned 2 results.

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Be careful while constructing your queries because the row-keys, column-family identifiers, and column keys are case sensitive. Therefore, passing in 'prius' instead of 'Prius' does not return any name-value tuples. Try running get Cars['prius'] via the CLI. You will receive a response that reads Returned 0 results. Also, before you query, remember to issue use CarDataStore to make CarDataStore the current keyspace.

jieforest

To access just the 'make' name-value data for the 'Prius' row you could query like so:

1. [default@CarDataStore] get Cars['Prius']['make'];
   
2. => (column=make, value=746f796f7461, timestamp=1301824068109000)

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Cassandra data sets can support richer data models than those shown so far and querying capabilities are also more complex than those illustrated, but I will leave those topics for a later chapter. For now, I am convinced you have had your first taste.

After walking through two simple examples, one that involved a document store, MongoDB, and another that involved a column database, Apache Cassandra, you may be ready to start interfacing with these using a programming language of your choice.

xin1shou3

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谢谢！