Hi Joel, thanks for the reply, actually we were not using field collapsing before, we basically want to replace grouping with that. The grouping performance between Solr 4 and 6 are basically comparable. It's surprising I got so big degradation with the field collapsing.
So basically the comparison we did were based on the Solr4 queries , extracted from logs, and modified slightly to include field collapsing parameter. To build the tests to compare Solr 4.10.2 to Solr 6 we basically proceeded in this way : 1) install Solr 4.10.2 and Solr 6.0.0 2) migrate the index with the related lucene tool ( 4.10.2 -> 5.5.0 -> Solr 6.0 ) 3) switch on/off the 2 instances and repeating the tests both with cold instances and warm instances. This means that the query looks the same. I have not double checked the results but only the timings. I will provide additional feedback to see if the query are producing comparable results as well. Related your suggestion about the top_fc, thanks, I will try that . I actually discovered that a little bit after I posted the mailing list ( I think exactly from another post of yours :) ) Not sure if setting up docValues for the field we use to collapse could give some benefit as well. I keep you updated, Cheers 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 > > > -- -------------------------- 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
