[CASSANDRA-8490] DISTINCT queries with LIMITs or paging are incorrect when partitions are deleted

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 2.0.12, 2.1.3

Environment

Driver version: 2.1.3.
Cassandra version: 2.0.11/2.1.2.

• Severity: Normal
• Assignee: Tom Hobbs Assign to me
• Reporter: Frank Limstrand

Authors

Tom Hobbs

Reviewers

Sylvain Lebresne

• Created: 16/Dec/14 09:13
• Updated: 16/Apr/19 09:31
• Resolved: 09/Jan/15 17:23

Description

Using paging demo code from https://github.com/PatrickCallaghan/datastax-paging-demo

The code creates and populates a table with 1000 entries and pages through them with setFetchSize set to 100. If we then delete one entry with 'cqlsh':

cqlsh:datastax_paging_demo> delete from datastax_paging_demo.products  where productId = 'P142'; (The specified productid is number 6 in the resultset.)

and run the same query ("Select * from") again we get:

[com.datastax.paging.Main.main()] INFO  com.datastax.paging.Main - Paging demo took 0 secs. Total Products : 999

which is what we would expect.

If we then change the "select" statement in dao/ProductDao.java (line 70) from "Select * from " to "Select DISTINCT productid from " we get this result:

[com.datastax.paging.Main.main()] INFO  com.datastax.paging.Main - Paging demo took 0 secs. Total Products : 99

So it looks like the tombstone stops the paging behaviour. Is this a bug?

DEBUG [Native-Transport-Requests:788] 2014-12-16 10:09:13,431 Message.java (line 319) Received: QUERY Select DISTINCT productid from datastax_paging_demo.products, v=2
DEBUG [Native-Transport-Requests:788] 2014-12-16 10:09:13,434 AbstractQueryPager.java (line 98) Fetched 99 live rows
DEBUG [Native-Transport-Requests:788] 2014-12-16 10:09:13,434 AbstractQueryPager.java (line 115) Got result (99) smaller than page size (100), considering pager exhausted