The rangeSafe SPARQL query hint

Use this query hint to turn off type promotion for a SPARQL query.

When you submit a SPARQL query that includes a FILTER over a numerical value or range, the Neptune query engine must normally use type promotion when it executes the query. This means that it has to examine values of every type that could hold the value you are filtering on.

For example, if you are filtering for values equal to 55, the engine must look for integers equal to 55, long integers equal to 55L, floats equal to 55.0, and so forth. Each type promotion requires an additional lookup on storage, which can cause an apparently simple query to take an unexpectedly long time to complete.

Often type promotion is unnecessary because you know in advance that you only need to find values of one specific type. When this is the case, you can speed up your queries dramatically by using the rangeSafe query hint to turn off type promotion.

rangeSafe SPARQL hint syntax

The rangeSafe query hint takes a value of true to turn off type promotion. It also accepts a value of false (the default).

Example. The following example shows how to turn off type promotion when filtering for an integer value of o greater than 1:

PREFIX hint: <http://aws.amazon.com/neptune/vocab/v01/QueryHints#>
SELECT * {
   ?s ?p ?o .
   hint:Prior hint:rangeSafe 'true' .
   FILTER (?o > '1'^^<http://www.w3.org/2001/XMLSchema#int>)