This component retrieves data on a Cassandra server and loads it into a 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.
Note: Cassandra Query defaults all object names to lowercase and thus lacks any case sensitivity in this respect. This can mean that, when looking for upper or mixed-case objects, the component will fail when it apparently should have succeeded (sometimes failing even when the component successfully validates). To enable case sensitivity, use the 'CaseSensitivity' option in the Connection Options property and set it to 'true'.
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.|
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 a method of comparing the column to the value. Possible comparators include: 'Equal To', 'Greater than', 'Less than', 'Greater than or equal to', 'Less than or equal to', 'Like', 'Null'.
'Equal To' can match exact strings and numeric values while other comparators such as 'Greater than' will work only with numerics. The 'Like' operator allows the wildcard character (%) to be used at the start and end of a string value to match a column. The Null operator matches only Null values, ignoring whatever the value is set to.
Not all data sources support all comparators, thus it is likely only a subset of the above comparators will be available to choose from.
|Value||The value to be compared.|
|SQL||Text||Custom SQL-like query only available during 'Advanced' mode.|
|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.|
|Warehouse||Select||Choose a Snowflake warehouse that will run the load.|
|Database||Select||Choose a database to create the new table in.|
|Type||Select||Choose between using a standard table or an external table.
Standard: The data will be staged on an S3 bucket before being loaded into a table.
External: The data will be put into an S3 Bucket and referenced by an external table.
|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.
Note: An external schema is required if the 'Type' property is set to 'External'.
|Target Table||Text||Provide a new table name.
Warning: This table will be recreated and will drop any existing table of the same name.
|Location||Text/Select||When using an 'External' type table, Provide an S3 Bucket path that will be used to store the data. Once on an S3 bucket, the data can be referenced by the external table.|
|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.
|Load Options||Multiple Selection||
Comp Update: Apply automatic compression to the target table (if ON). Default is ON.
Stat Update: Automatically update statistics when filling a table (if ON). Default is ON. In this case, it is updating the statistics of the target table.
Clean S3 Objects: Automatically remove UUID-based objects on the S3 Bucket (if ON). Default is ON. Effectively decides whether to keep the staged data in the S3 Bucket or not.
String Null is Null: Converts any strings equal to "null" into a null value. This is case sensitive and only works with entirely lower-case strings. Default is ON.
Recreate Target Table:Choose whether the component recreates its target table before the data load. If OFF, the existing table will be used. Default is ON.
|Project||Text||The target BigQuery project to load data into.|
|Dataset||Text||The target BigQuery dataset to load data into.|
|Cloud Storage Staging Area||Text||The URL and path of the target Google Storage bucket to be used for staging the queried data.|
|Encryption||Select||Decide on how the files are encrypted inside the S3 Bucket.
None: No encryption.
SSE KMS: Encrypt the data according to a key stored on KMS.
SSE S3: Encrypt the data according to a key stored on an S3 bucket
|KMS Key ID||Select||The ID of the KMS encryption key you have chosen to use in the 'Encryption' property.|
This component makes the following values available to export into variables:
|Time Taken To Stage||The amount of time (in seconds) taken to fetch the data from the data source and upload it to storage.|
|Time Taken To Load||The amount of time (in seconds) taken to execute the COPY statement to load the data into the target table from storage.|
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 table. The job begins by creating a table on the database, 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 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 table.