For exact syntax of the top_fc hint use the official docs. The blog is using an upper case hint, but that was changed to a lower case hint.
Joel Bernstein http://joelsolr.blogspot.com/ On Mon, May 23, 2016 at 2:56 PM, Joel Bernstein <joels...@gmail.com> wrote: > Also I wrote a guide for Solr 5 Collapsing/Expand performance, that use to > be on Heliosearch.org. It's now long available accept through the magic of > the Wayback machine. What's not covered is the sort param, which came later. > > Here it is: > > > http://web.archive.org/web/20150709154420/http://heliosearch.org/solr5-collapse-expand > > Joel Bernstein > http://joelsolr.blogspot.com/ > > On Mon, May 23, 2016 at 2:48 PM, Joel Bernstein <joels...@gmail.com> > wrote: > >> Were you using the sort param or min/max param in Solr 4 to select the >> group head? The sort work came later and I'm not sure how it compares in >> performance to the min/max param. >> >> Since you are collapsing on a string field you can use the top_fc hint >> which will use a top level field cache for the collapse. This is faster at >> query time then the default which uses MultiDocValue ordinal map. >> >> The docs cover the top_fc hint. >> https://cwiki.apache.org/confluence/display/solr/Collapse+and+Expand+Results >> >> >> >> Joel Bernstein >> http://joelsolr.blogspot.com/ >> >> On Mon, May 23, 2016 at 12:14 PM, Alessandro Benedetti < >> abenede...@apache.org> wrote: >> >>> Let's add some additional details guys : >>> >>> 1) *Faceting* >>> Currently the facet method used is "enum" and it runs over 20 fields more >>> or less. >>> Mainly using it on low cardinality fields except one which has a >>> cardinality of 1000 terms. >>> I am aware of the famous Jira related faceting regression : >>> https://issues.apache.org/jira/browse/SOLR-8096 . >>> >>> Our index is indeed quite static ( we index once per day) and the fields >>> we >>> facet on are multi-valued ( by schema definition but not in practise) . >>> But we use Term Enum as method so i was not expecting to hit the >>> regression. >>> We currently see query times which are 30% worse than Solr 4.10.2 . >>> Our next experiment will be to enable docValues for all the fields and >>> verify if we get any benefit ( switching the facet method to fc) . >>> At the moment, switching to json faceting is not an option as we would >>> like >>> first to proceed with a transparent migration and then possibly add >>> improvements and refactor in the future. >>> Following will be to fix the schema to set as multi valued only what is >>> really multi-valued ( do you know if this can affect ? the wrong schema >>> definition is enough to mess up the facet performance ? even if then the >>> fields are single valued ?) >>> >>> >>> 2) *Field Collapsing* >>> Field collapsing performance seems much, much worse, something like 200 >>> ms >>> ( Solr 4) vs 1800 ms ( Solr 6) . >>> This is suprising as I never heard about any regression in field >>> collapsing. >>> I will investigate a little bit more in details about the internals of >>> the >>> field collapsing and why the performance could be so degraded. >>> I will also verify if I find any info in the mailing list or Jira. >>> >>> &fq={!collapse field=string_field sort='TrieDoubleField asc'} >>> >>> let me know if you faced something similar >>> >>> Cheers >>> >>> On Fri, May 13, 2016 at 10:41 PM, Alessandro Benedetti < >>> abenede...@apache.org> wrote: >>> >>> > I'm planning a migration from 4.10.2 to 6.0 . >>> > Because we generate the index on daily basis from scratch, we don't >>> need >>> > to migrate the index but actually only migrate the server instances. >>> > With my team we were doing some experiments on some dev machines, >>> > basically comparing Solr 4.10.2 and Solr 6.0 to check any functional >>> and >>> > performance regression in our use cases. >>> > >>> > After setting up two installation on the same machine ( switching on >>> and >>> > off each version for doing comparison and experiments) we are >>> verifying a >>> > degradation of the performances with Solr 6. >>> > >>> > Basically from a queryTime and throughput perspective Solr 6 is not >>> > performing as well as Solr 4.10.2 . >>> > Still need to start the proper investigations but this appears weird >>> to me. >>> > Will proceed with all the analysis of the case and a deep study of our >>> > queries ( which anyway are mainly fq , faceting and grouping). >>> > >>> > Any suggestion in particular to start with ? Has anyone experienced a >>> > similar migration with similar experience ? >>> > I will anyway explore also the mailing list in search for similar >>> cases. >>> > >>> > Cheers >>> > >>> > -- >>> > -------------------------- >>> > >>> > Benedetti Alessandro >>> > Visiting card : http://about.me/alessandro_benedetti >>> > >>> > "Tyger, tyger burning bright >>> > In the forests of the night, >>> > What immortal hand or eye >>> > Could frame thy fearful symmetry?" >>> > >>> > William Blake - Songs of Experience -1794 England >>> > >>> >>> >>> >>> -- >>> -------------------------- >>> >>> Benedetti Alessandro >>> Visiting card : http://about.me/alessandro_benedetti >>> >>> "Tyger, tyger burning bright >>> In the forests of the night, >>> What immortal hand or eye >>> Could frame thy fearful symmetry?" >>> >>> William Blake - Songs of Experience -1794 England >>> >> >> >
