Gremlin typePromotion query hint - Amazon Neptune
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Gremlin typePromotion query hint

When you submit a Gremlin traversal that filters on 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.

Let's say you are searching for all vertexes with a customer-age property greater than 5:

g.V().has('customerAge', gt(5))

To execute that traversal thoroughly, Neptune must expand the query to examine every numeric type that the value you are querying for could be promoted to. In this case, the gt filter has to be applied for any integer over 5, any long over 5L, any float over 5.0, and any double over 5.0. Because each of these type promotions requires an additional lookup on storage, you will see multiple filters per numeric filter when you run the Gremlin profile API for this query, and it will take significantly longer to complete than you might expect.

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 typePromotion query hint to turn off type promotion.

Syntax

The typePromotion query hint is specified by adding a withSideEffect step to the query.

g.withSideEffect('Neptune#typePromotion', true or false).gremlin-traversal
Note

All Gremlin query hints side effects are prefixed with Neptune#.

Available Values

  • true

  • false

To turn off type promotion for the query above, you would use:

g.withSideEffect('Neptune#typePromotion', false).V().has('customerAge', gt(5))