When using the Dynamic Re-Ranking (DRR) simulator, if you hover over the "Dynamic Re-Ranking" ranking factor you will see the message :
"X items impacted out of the first 100 results”
But what does this actually mean?
By design, the DRR simulator only returns and analyses the first 100 results of a query. This means that the number of “impacted” items shown is limited to those that appear in these top 100 results.
However, DRR is not limited to only re-ranking the top 100 items. It can re-rank items from anywhere in a results set. This means an item originally returned in 200th position could still be boosted by DRR but if the re-ranking doesn’t bring it into the top 100, the simulator won’t count it.
For example, let’s say you have 100 items pinned by a merchandising rule, and 2 items pinned by DRR to position 101 and 102 (note that rules that pin items are applied after re-ranking so that they keep working as expected).
Since the two DRR-impacted items aren’t visible in the first 100 results (because the pinned items take all the top spots), the simulator will display “0 items impacted out of the first 100 results”.
This does not mean DRR had no effect, it simply means that its impact isn't visible within the top 100 results shown in the simulator.