[CASSANDRA-6151] CqlPagingRecorderReader Used when Partition Key Is Explicitly Stated

• Type: Bug
• Status: Resolved
• Priority: Low
• Resolution: Won't Fix
• Severity: Low
• Assignee: Alex Liu
• Reporter: Russell Spitzer

Authors

Alex Liu

Reviewers

Jonathan Ellis

• Created: 06/Oct/13 17:28
• Updated: 16/Apr/19 09:32
• Resolved: 21/Nov/13 23:44

Description

From http://stackoverflow.com/questions/19189649/composite-key-in-cassandra-with-pig/19211546#19211546

The user was attempting to load a single partition using a where clause in a pig load statement.

CQL Table

CREATE table data (
  occurday  text,
  seqnumber int,
  occurtimems bigint,
  unique bigint,

  fields map<text, text>,

  primary key ((occurday, seqnumber), occurtimems, unique)
)

Pig Load statement Query

data = LOAD 'cql://ks/data?where_clause=seqnumber%3D10%20AND%20occurday%3D%272013-10-01%27' USING CqlStorage();    

This results in an exception when processed by the the CqlPagingRecordReader which attempts to page this query even though it contains at most one partition key. This leads to an invalid CQL statement.

CqlPagingRecordReader Query

SELECT * FROM "data" WHERE token("occurday","seqnumber") > ? AND
token("occurday","seqnumber") <= ? AND occurday='A Great Day' 
AND seqnumber=1 LIMIT 1000 ALLOW FILTERING

Exception

 InvalidRequestException(why:occurday cannot be restricted by more than one relation if it includes an Equal)

I'm not sure it is worth the special case but, a modification to not use the paging record reader when the entire partition key is specified would solve this issue.

Solution

If it have EQUAL clauses for all the partitioning keys, we use Query

  SELECT * FROM "data" 
  WHERE occurday='A Great Day' 
       AND seqnumber=1 LIMIT 1000 ALLOW FILTERING

instead of

  SELECT * FROM "data" 
  WHERE token("occurday","seqnumber") > ? 
   AND token("occurday","seqnumber") <= ? 
   AND occurday='A Great Day' 
   AND seqnumber=1 LIMIT 1000 ALLOW FILTERING

The base line implementation is to retrieve all data of all rows around the ring. This new feature is to retrieve all data of a wide row. It's a one level lower than the base line. It helps for the use case where user is only interested in a specific wide row, so the user doesn't spend whole job to retrieve all the rows around the ring.

Issue Links

• is related to: CASSANDRA-6238 LOCAL_ONE doesn't work for SimpleStrategy
• relates to: CASSANDRA-6238 LOCAL_ONE doesn't work for SimpleStrategy