The CollapsingQParserPlugin can be resource intensive so you'll want to be careful about how it's used. Particularly with autowarming in the queryResultCache. If you autowarm lots of queries while using the CollapsingQParserPlugin, your be running lots of CPU and memory intensive queries after opening a new searcher.
Also you'll want to understand the memory profile for the CollapsingQParserPlugin on your index. It uses more memory as the number of unique values in the collapse field grows. This is regardless of the number of unique values in the search results. So, be aware of the cardinality of the collapse field and use the nullPolicy=expand, if you have nulls in the collapsed field. This null policy is designed to lesson the memory impact if there a nulls in the collapsed field. Also it's a good idea to have one static warming query that exercises the CollapsingQParserPlugin as it can take time to warm. Autowarming the query result cache might cover this in your case. In general the CollapsingQParserPlugin should be faster then grouping when you have a high number of distinct groups in the result set. But the tradeoff is that it it's more memory intensive then grouping when there is a low number of distinct groups in the result set. Both the collapsingqparserpluging and grouping (with ngroups) have a high memory footprint when there is a large number of distinct groups in the result set. If your not using ngroups, grouping will always outperform the collapsingqparserplugin. Joel Bernstein Search Engineer at Heliosearch On Tue, Jun 3, 2014 at 12:38 PM, Jean-Sebastien Vachon < jean-sebastien.vac...@wantedanalytics.com> wrote: > Yes we are already using it. > > > -----Original Message----- > > From: Otis Gospodnetic [mailto:otis.gospodne...@gmail.com] > > Sent: June-03-14 11:41 AM > > To: solr-user@lucene.apache.org > > Subject: Re: Strange behaviour when tuning the caches > > > > Hi, > > > > Have you seen https://wiki.apache.org/solr/CollapsingQParserPlugin ? > May > > help with the field collapsing queries. > > > > Otis > > -- > > Performance Monitoring * Log Analytics * Search Analytics Solr & > > Elasticsearch Support * http://sematext.com/ > > > > > > On Tue, Jun 3, 2014 at 8:41 AM, Jean-Sebastien Vachon < jean- > > sebastien.vac...@wantedanalytics.com> wrote: > > > > > Hi Otis, > > > > > > We saw some improvement when increasing the size of the caches. Since > > > then, we followed Shawn advice on the filterCache and gave some > > > additional RAM to the JVM in order to reduce GC. The performance is > > > very good right now but we are still experiencing some instability but > > > not at the same level as before. > > > With our current settings the number of evictions is actually very low > > > so we might be able to reduce some caches to free up some additional > > > memory for the JVM to use. > > > > > > As for the queries, it is a set of 5 million queries taken from our > > > logs so they vary a lot. All I can say is that all queries involve > > > either grouping/field collapsing and/or radius search around a point. > > > Our largest customer is using a set of 8-10 filters that are > > > translated as fq parameters. The collection contains around 13 million > > > documents distributed on 5 shards with 2 replicas. The second > > > collection has the same configuration and is used for indexing or as a > > > fail-over index in case the first one falls. > > > > > > We`ll keep making adjustments today but we are pretty close of having > > > something that performs while being stable. > > > > > > Thanks all for your help. > > > > > > > > > > > > > -----Original Message----- > > > > From: Otis Gospodnetic [mailto:otis.gospodne...@gmail.com] > > > > Sent: June-03-14 12:17 AM > > > > To: solr-user@lucene.apache.org > > > > Subject: Re: Strange behaviour when tuning the caches > > > > > > > > Hi Jean-Sebastien, > > > > > > > > One thing you didn't mention is whether as you are increasing(I > > > > assume) cache sizes you actually see performance improve? If not, > > > > then maybe > > > there > > > > is no value increasing cache sizes. > > > > > > > > I assume you changed only one cache at a time? Were you able to get > > > > any one of them to the point where there were no evictions without > > > > things breaking? > > > > > > > > What are your queries like, can you share a few examples? > > > > > > > > Otis > > > > -- > > > > Performance Monitoring * Log Analytics * Search Analytics Solr & > > > > Elasticsearch Support * http://sematext.com/ > > > > > > > > > > > > On Mon, Jun 2, 2014 at 11:09 AM, Jean-Sebastien Vachon < jean- > > > > sebastien.vac...@wantedanalytics.com> wrote: > > > > > > > > > Thanks for your quick response. > > > > > > > > > > Our JVM is configured with a heap of 8GB. So we are pretty close > > > > > of the "optimal" configuration you are mentioning. The only other > > > > > programs running is Zookeeper (which has its own storage device) > > > > > and a proprietary API (with a heap of 1GB) we have on top of Solr > > > > > to server > > > our > > > > customer`s requests. > > > > > > > > > > I will look into the filterCache to see if we can better use it. > > > > > > > > > > Thanks for your help > > > > > > > > > > > -----Original Message----- > > > > > > From: Shawn Heisey [mailto:s...@elyograg.org] > > > > > > Sent: June-02-14 10:48 AM > > > > > > To: solr-user@lucene.apache.org > > > > > > Subject: Re: Strange behaviour when tuning the caches > > > > > > > > > > > > On 6/2/2014 8:24 AM, Jean-Sebastien Vachon wrote: > > > > > > > We have yet to determine where the exact breaking point is. > > > > > > > > > > > > > > The two patterns we are seeing are: > > > > > > > > > > > > > > - less cache (around 20-30% hit/ratio), poor > performance > > > but > > > > > > > overall good stability > > > > > > > > > > > > When caches are too small, a low hit ratio is expected. > > > > > > Increasing them > > > > > is a > > > > > > good idea, but only increase them a little bit at a time. The > > > > > filterCache in > > > > > > particular should not be increased dramatically, especially the > > > > > > autowarmCount value. Filters can take a very long time to > > > > > > execute, so a > > > > > high > > > > > > autowarmCount can result in commits taking forever. > > > > > > > > > > > > Each filter entry can take up a lot of heap memory -- in terms > > > > > > of bytes, > > > > > it is > > > > > > the number of documents in the core divided by 8. This means > > > > > > that if the core has 10 million documents, each filter entry > > > > > > (for JUST that > > > > > > core) will take over a megabyte of RAM. > > > > > > > > > > > > > - more cache (over 90% hit/ratio), improved > performance > > > but > > > > > > > almost no stability. In that case, we start seeing messages > > > > > > > such as "No shards hosting shard X" or "cancelElection did not > > > > > > > find election node to remove" > > > > > > > > > > > > This would not be a direct result of increasing the cache size, > > > > > > unless > > > > > perhaps > > > > > > you've increased them so they are *REALLY* big and you're > > > > > > running out of RAM for the heap or OS disk cache. > > > > > > > > > > > > > Anyone, has any advice on what could cause this? I am > > > > > > > beginning to suspect the JVM version, is there any minimal > > > > > > > requirements regarding the JVM? > > > > > > > > > > > > Oracle Java 7 is recommended for all releases, and required for > > > > > > Solr > > > > > 4.8. You > > > > > > just need to stay away from 7u40, 7u45, and 7u51 because of bugs > > > > > > in Java itself. Right now, the latest release is recommended, > > > > > > which is > > > 7u60. > > > > > The > > > > > > 7u21 release that you are running should be perfectly fine. > > > > > > > > > > > > With six 9.4GB cores per node, you'll achieve the best > > > > > > performance if you have about 60GB of RAM left over for the OS > > > > > > disk cache to use > > > > > > -- the > > > > > size of > > > > > > your index data on disk. You did mention that you have 92GB of > > > > > > RAM per node, but you have not said how big your Java heap is, > > > > > > or whether there > > > > > is > > > > > > other software on the machine that may be eating up RAM for its > > > > > > heap or data. > > > > > > > > > > > > http://wiki.apache.org/solr/SolrPerformanceProblems > > > > > > > > > > > > Thanks, > > > > > > Shawn > > > > > > > > > > > > ----- > > > > > > Aucun virus trouvé dans ce message. > > > > > > Analyse effectuée par AVG - www.avg.fr > > > > > > Version: 2014.0.4570 / Base de données virale: 3950/7571 - Date: > > > > > > 27/05/2014 > > > > > > > > > > > > > ----- > > > > Aucun virus trouvé dans ce message. > > > > Analyse effectuée par AVG - www.avg.fr > > > > Version: 2014.0.4570 / Base de données virale: 3950/7571 - Date: > > > > 27/05/2014 La Base de données des virus a expiré. > > > > > > > ----- > > Aucun virus trouvé dans ce message. > > Analyse effectuée par AVG - www.avg.fr > > Version: 2014.0.4570 / Base de données virale: 3950/7571 - Date: > > 27/05/2014 La Base de données des virus a expiré. >
