Hi,
While upgrading to Solr 8 from 6 the Unified highlighter begins to have
performance issues going from approximately 100ms to more than 4 seconds
with 76 fields in the hl.q and hl.fl parameters. So I played with
different options and found that the hl.q parameter needs to have any one
field for the performance issue to vanish. I do not know why this would be
so. Could you check if this is a bug or something else? This is not the
case if I use the original highlighter which has same performance on Solr 6
and Solr 8 of ~ 1.5 seconds. The highlighting payload is also mostly same
in all the cases.
Prior Solr 8 configuration with bad performance of > 4sec
<str name="hl.q">{!edismax qf="field1 field2 ..field76" v=$qq}</str>
<str name="hl.fl">field1 field2 ..field76</str>
Solr 8 configuration with original Solr 6 performance of ~ 100 ms
<str name="hl.q">{!edismax qf="field1" v=$qq}</str>
<str name="hl.fl">field1 field2 ..field76</str>
Other highlighting parameters
<str name="hl">true</str>
<str name="hl.method">unified</str>
<str name="hl.fragsize">200</str>
<str name="f.resume.content.hl.bs.type">WORD</str>
<str name="hl.bs.language">en</str>
<str name="hl.snippets">10</str>
If I remove the hl.q parameter altogether, the performance time shoots up
to 6-7 seconds, since our user query is quite large with more fields and is
more complicated, I suspect.
