Grouping does need 3 phases.. The phases are: (1) Each shard is asked for the top N groups (instead of ids), with the sort value. The federator then sorts the groups from all shards and chooses the top N groups. (2) For the N groups, each shard is asked for the top M ids (M is configurable per request). The top M ids from each shard for every group is again sorted within each group to find the overall top M. At the end of this phase, you have the top N groups with the top M ids for each group. (3) The final phase gets the stored fields for these M*N ids. On 20 Aug 2015 20:00, "SolrUser1543" <osta...@gmail.com> wrote:
> I want to understand, why number of requests in SOLD CLOUD is different > with > and without using of grouping feature. > > > 1. suppose we have several shards in SOLR CLOUD ( lets say 3 shards ) > 2. One of them, gets a query with rows = n > 3. This shards distributes a request among others and suppose that every > shard has a lot of results , much more than n . > 4. Then it receives an item IDs from each shards , so the number of results > in total is 3n > 5. Then it sorts the results and chooses the best n results , when in my > case each shard has representatives in total results . > 6. Then it send a second request to each shard , with appropriate item IDs > , > to get a stored fields . > > So then in this case ,each shard will be queried twice, first one to get > item IDs , and the second to get stored fields . > > That is what I see in my logs . ( I see 6 log entries , 2 for each shard ) > > *The question is , why when I am using a grouping feature, the number of > request to each shard is 3 instead of 2 times ?* ( I see 8 or 9 log > entries > ) > > > > > -- > View this message in context: > http://lucene.472066.n3.nabble.com/Number-of-requests-to-each-shard-is-different-with-and-without-using-of-grouping-tp4224293.html > Sent from the Solr - User mailing list archive at Nabble.com. >
