Spring Batch Paging with sortKeys and parameter values

Question

I have a Spring Batch project running in Spring Boot that is working perfectly fine. For my reader I'm using JdbcPagingItemReader with a MySqlPagingQueryProvider.

@Bean
public ItemReader<Person> reader(DataSource dataSource) {
    MySqlPagingQueryProvider provider = new MySqlPagingQueryProvider()
    provider.setSelectClause(ScoringConstants.SCORING_SELECT_STATEMENT)
    provider.setFromClause(ScoringConstants.SCORING_FROM_CLAUSE)
    provider.setSortKeys("p.id": Order.ASCENDING)

    JdbcPagingItemReader<Person> reader = new JdbcPagingItemReader<Person>()
    reader.setRowMapper(new PersonRowMapper())
    reader.setDataSource(dataSource)
    reader.setQueryProvider(provider)
    //Setting these caused the exception
    reader.setParameterValues(
        startDate: new Date() - 31,
        endDate: new Date()
    ) 
    reader.afterPropertiesSet()
    return reader
}

However, when I modified my query with some named parameters to replace previously hard coded date values and set these parameter values on the reader as shown above, I get the following exception on the second page read (the first page works fine because the _id parameter hasn't been made use of by the paging query provider):

org.springframework.dao.InvalidDataAccessApiUsageException: No value supplied for the SQL parameter '_id': No value registered for key '_id'
at org.springframework.jdbc.core.namedparam.NamedParameterUtils.buildValueArray(NamedParameterUtils.java:336)
at org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.getPreparedStatementCreator(NamedParameterJdbcTemplate.java:374)
at org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.query(NamedParameterJdbcTemplate.java:192)
at org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.query(NamedParameterJdbcTemplate.java:199)
at org.springframework.batch.item.database.JdbcPagingItemReader.doReadPage(JdbcPagingItemReader.java:218)
at org.springframework.batch.item.database.AbstractPagingItemReader.doRead(AbstractPagingItemReader.java:108)

Here is an example of the SQL, which has no WHERE clause by default. One does get created automatically when the second page is read:

select *, (select id from family f where date_created between :startDate and :endDate and f.creator_id = p.id)  from person p

On the second page, the sql is modified to the following, however it seems that the named parameter for _id didn't get supplied:

select *, (select id from family f where date_created between :startDate and :endDate and f.creator_id = p.id) from person p WHERE id > :_id

I'm wondering if I simply can't use the MySqlPagingQueryProvider sort keys together with additional named parameters set in JdbcPagingItemReader. If not, what is the best alternative to solving this problem? I need to be able to supply parameters to the query and also page it (vs. using the cursor). Thank you!

Answer 1

I solved this problem with some intense debugging. It turns out that MySqlPagingQueryProvider utilizes a method getSortKeysWithoutAliases() when it builds up the SQL query to run for the first page and for subsequent pages. It therefore appends and (p.id > :_id) instead of and (p.id > :_p.id). Later on, when the second page sort values are created and stored in JdbcPagingItemReader's startAfterValues field it will use the original "p.id" String specified and eventually put into the named parameter map the pair ("_p.id",10). However, when the reader tries to fill in _id in the query, it doesn't exist because the reader used the non-alias removed key.

Long story short, I had to remove the alias reference when defining my sort keys.

provider.setSortKeys("p.id": Order.ASCENDING)

had to change to in order for everything to work nicely together

provider.setSortKeys("id": Order.ASCENDING)

Answer 2

I had the same issue and got another possible solution.

My table T has a primary key field INTERNAL_ID.

The query in JdbcPagingItemReader was like this:

SELECT INTERNAL_ID, ... FROM T WHERE ... ORDER BY INTERNAL_ID ASC

So, the key is: in some conditions, the query didn't return results, and then, raised the error above No value supplied for...

The solution is:

• Check in a Spring Batch decider element if there are rows.
• If it is, continue with chunk: reader-processor-writer.
• It it's not, go to another step.

Please, note that they are two different scenarios:

• At the beginning, there are rows. You get them by paging and finally, there are no more rows. This has no problem and decider trick is not required.
• At the beginning, there are no rows. Then, this error raised, and the decider solved it.

Hope this helps.