This component retrieves data on a Cassandra server and loads it into a Redshift table. This stages the data, so the table is reloaded each time. You may then use transformations to enrich and manage the data in permanent tables.
Warning: This component is destructive as it truncates or recreates its target table on each run. Do not modify the target table structure manually.
|Name||Text||The descriptive name for the component.|
|Basic/Advanced Mode||Choice||Basic - This mode will build a Query for you using settings from Data Source, Data Selection and Data Source Filter parameters. In most cases, this will be sufficient.
Advanced - This mode will require you to write an SQL-like query to call data from Cassandra. The available fields and their descriptions are documented in the data model.
|Server||Choice||Address of the Cassandra server from which data is to be sourced.|
|User||Text||Login name for the Cassandra server.|
|Password||Text||Login password for the Cassandra server.|
|Database||Text||The name of the database you wish to source data from.|
|Data Source||Choice||Select a data source from the server.|
|Data Selection||Choice||Select one or more columns to return from the query.|
|Data Source Filter||Input Column||The available input columns vary depending upon the Data Source.|
|Qualifier||Is - Compares the column to the value using the comparator.
Not - Reverses the effect of the comparison, so "equals" becomes "not equals", "less than" becomes "greater than or equal to" etc.
|Comparator||Choose one of Equal To, Greater than, Less than, Greater than or equal to, Less than or equal to.|
|Value||The value to be compared.|
|SQL||Text||Custom SQL-like query only available during 'Advanced' mode.|
|Combine Filters||Text||Use the defined filters in combination with one another according to either "and" or "or".|
|Limit||Number||Limits the number of rows that are loaded from file.|
|Connection Options||Parameter||A JDBC parameter supported by the Database Driver. The available parameters are determined automatically from the driver, and may change from version to version.
They are usually not required as sensible defaults are assumed.
|Value||A value for the given Parameter.|
|S3 Staging Area||Text||The name of an S3 bucket for temporary storage. Ensure your access credentials have S3 access and permission to write to the bucket. See this document for details on setting up access. The temporary objects created in this bucket will be removed again after the load completes, they are not kept.|
|Schema||Select||Select the table schema. The special value, [Environment Default] will use the schema defined in the environment. For more information on using multiple schemas, see this article.|
|Target Table||Text||Provide a new table name.
Warning: This table will be recreated and will drop any existing table of the same name.
|Distribution Style||Select||Even - the default option, distribute rows around the Redshift Cluster evenly.
All - copy rows to all nodes in the Redshift Cluster.
Key - distribute rows around the Redshift cluster according to the value of a key column.
Table-distribution is critical to good performance - see the Amazon Redshift documentation for more information.
|Sort Key||Select||This is optional, and specifies the columns from the input that should be set as the table's sort-key.
Sort-keys are critical to good performance - see the Amazon Redshift documentation for more information.
This component makes the following values available to export into variables:
|Component||Name of the component.|
|Status||Successful or Unsuccessful.|
|Started At||Time Component began.|
|Completed At||Time Component finished.|
|Duration||Duration of Components run.|
|Row Count||Number of Rows queried by the component.|
|Message||Any messages yielded by the component (usually empty).|
Connect to the target database and issue the query. Stream the results into objects on S3. Then create or truncate the target table and issue a COPY command to load the S3 objects into the table. Finally, clean up the temporary S3 objects.
This example will take data from a Cassandra database and load it into a Redshift Table. The job begins by creating a table on the Redshift server, then the Cassandra Query Component is used to take data from Cassandra, copy it to an S3 bucket and then finally load it into the Redshift table.
Create/Replace Table Component is used to make the table 'Example_Cassandra', which is then entered into the Cassandra Query Component's Target Table field. Details regarding the Cassandra server and login credentials are added and a data source is chosen. Since we want all of the data, there is no need to add to the 'Data Source Filter' or 'Limit' properties. Similarly, a Sort Key is not required but is recommended for large tables.
Note that the table must exist before Cassandra Query is run. Running the Create/Replace component table first will create the table, then the Cassandra Query or the entire job can be run to load data from Cassandra into the Redshift table.