HI all,
On our current master/slave setup (no cloud), we use a a custom sorting
function to get the first pass results (using the sort param), and then we
use LTR for re-ranking. This works fine, i.e. re-ranking is applied on the
topN, after sorting has completed and the order is correct.
However, as we are migrating on SolrCloud (version 7.3.1) with multiple
shards, this does not seem to work as expected. To my understanding, Solr
collects the reranked results from the shards back on a single node to
merge them, and then tries to re-apply sorting.
We would expect the results to at least follow the sorting formula, even if
this is not what we want. But this still not even the case, as the
combination of the two (sorting + reranking) results in erratic ordering.
Example result, where $sort_score is the sorting formula output, and score
is the LTR re-ranked output:
{"id": "152",
"$sort_score": 17.38543,
"score": 0.22140852
},
{"id": "2016",
"$sort_score": 14.612957,
"score": 0.19214153
},
{ "id": "1523",
"$sort_score": 14.4093275,
"score": 0.26738763
},
{ "id": "6704",
"$sort_score": 13.956842,
"score": 0.17357588
},
{ "id": "6512",
"$sort_score": 14.43907,
"score": 0.11575622
},
We also tried with other simple re-rank queries apart from LTR, and the
issue persisted.
Could someone please help troubleshoot? Ideally, we would want to have the
re-rank results merged on the single node, and not re-apply sorting.
Thank you!
