How to get CustomerId from millions of records using Xquery in Marklogic

Question

We have a large database, and I am supposed to get only CustomerId's from the entire database without compromising the performance. What is the best way to do it?

Answer 1

If you are looking to report all of the CustomerId values from a large database, then having some sort of backing index will be the fastest and most efficient. With an index, retrieving the distinct list of values from a lexicon with a functions such as:

• cts:values() eg cts:values(cts:element-reference('CustomerId')) or cts:values(cts:path-reference('/Customer/CustomerId'))
• cts:element-values() eg cts:element-values(xs:QName("CustomerId"))

You could also create a TDE that has a CustomerId field and retrieve the values with an Optic query.

If you wanted to report the values without creating an index, then you could create a CoRB batch job to select the docs that have that element, return the value(s) from the process module, and write the values to an output file apply the EXPORT-FILE-SORT=ascending|distinct option.