JdbcPagingItemReader [BATCH-2465]

[spring-projects-issues]

cm opened BATCH-2465 and commented

if sortKeys is't unique key, the query sql(remainingPagesSql)---'select a,b,c from table where c>? limit 2' can lose data,for example:
a b c
1 2 1
2 2 2
3 3 2
4 5 3
the third row will lose.
remainingPagesSql --- 'select a,b,c from table limit pageSize*(pageNo-1),pageSize' and the last querySql --- 'select a,b,c from table limit pageSize*(pageNo-1),the sum of the table - pageSize*pageNo' is OK?

---

Affects: 3.0.6

Referenced from: pull request #568, and commits 9bd7c1b, 54f3a5c

Backported to: 3.0.9

[spring-projects-issues]

Michael Minella commented

This isn't a bug. It's how it's designed. After reviewing the documentation, I guess we don't explicitly state that anywhere from what I can find. We can update the documentation accordingly.

[spring-projects-issues]

Mahmoud Ben Hassine commented

@ Michael Minella I do confirm, I can't find any information about that in the documentation neither.

Just for the record, I add a reference to a related question on the forum here: http://forum.spring.io/forum/spring-projects/batch/89552-problem-in-jdbcpagingitemreader-with-timestamp-as-sortkey

Based on the reply by Dave Syer, I will update the reference documentation and the Javadoc to mention that it is important to have a unique key constraint on the sort key to guarantee that no data is lost between executions.