Improve recommendations for indexing metadata tables

[vpavic]

Recommendations for Indexing Metadata Tables section of the reference manual provides some guidance for indexing Spring Batch tables. However, this is focused solely on where clauses in SQL statements while it should arguably also consider foreign keys as indexing those plays important role in speeding up queries involving joins.

On PostgreSQL, detecting such columns can be done using something like this.

[wondywang]

I hope someone can provide the best solution for MySQL or Oracle.