If you can make min/max work for you instead of sort then it should be faster, but I haven't spent time comparing the performance.
But if you're using the top_fc with the min/max param the performance between Solr 4 & Solr 6 should be very close as the data structures behind them are the same. Joel Bernstein http://joelsolr.blogspot.com/ On Mon, May 23, 2016 at 3:34 PM, Alessandro Benedetti <abenede...@apache.org > wrote: > 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 >
