Creating a URL-encoded prepared statement (deprecated)

Pig demo examples set up a prepared CQL query using the output_query statement.

1. Format the data

   The example of saving Pig relations from/to Cassandra shows the output schema: the name of the simple_table1 table primary key 'a', represented as a chararray in the relation is paired with a value in the simple_table2 table. In this case, the key for simple_table1 table is only a partitioning key, and only a single tuple is needed.

   The Pig statement to add (moredata) fields to a tuple is:

   grunt> insertformat= FOREACH morevalues GENERATE
            TOTUPLE(TOTUPLE('a',x)),TOTUPLE(y);

   The example of exploring library data works with more complicated data, a partition key and clustering column:

   grunt> insertformat = FOREACH moredata GENERATE
            TOTUPLE(TOTUPLE('a',x),TOTUPLE('b',y),TOTUPLE('c',z)),TOTUPLE(data);

2. Construct the prepared query

   The output query portion of the cql:// URL is the prepared statement. The prepared statement must be url-encoded to make special characters readable by Pig.

   The example of saving Pig relations from/to Cassandra shows how to construct a prepared query:

   'cql://cql3ks/simple_table1?output_query=UPDATE+cql3ks.simple_table1+set+b+%3D+%3F'

   The key values of the simple_table1 table are automatically transformed into the 'WHERE (key) =' clause to form the output_query portion of a prepared statement.

3. Execute the query

   To update the simple_table1 table using the values in the simple_table2 (4-6), the prepared statement is executed using these WHERE clauses when the MapReduce job runs:

   ... WHERE a = 5
   ... WHERE a = 4
   ... WHERE a = 6

   This output_query in Pig statement forms the '...' url-encoded portion of the prepared statement:

   grunt> STORE insertformat INTO
            'cql://cql3ks/simple_table1?output_query=UPDATE+cql3ks.simple_table1+set+b+%3D+%3F'
            USING CqlNativeStorage;

   Decoded the UPDATE statement is:

   UPDATE cql3ks.simple_table1 SET b = ?

   The prepared statement represents these queries:

   UPDATE cql3ks.test SET b = 5 WHERE a = 5;
   UPDATE cql3ks.test set b = 4 WHERE a = 4;
   UPDATE cql3ks.test set b = 6 WHERE a = 6;