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From Apache Wiki <wikidi...@apache.org>
Subject [Solr Wiki] Update of "SolrTerminology" by ShawnHeisey
Date Wed, 18 Sep 2013 21:23:21 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Solr Wiki" for change notification.

The "SolrTerminology" page has been changed by ShawnHeisey:
https://wiki.apache.org/solr/SolrTerminology?action=diff&rev1=22&rev2=23

Comment:
slight changes on shard in the SolrCloud list  and Solr Core in the general list.

   * '''''Core''''': This is discussed in the General list (below) as Solr Core.  One difference
with SolrCloud is that the config it uses is in Zookeeper.  With traditional Solr, the core's
config will be in the conf directory on the disk.
   * '''''Leader''''': The shard replica that has won the leader election.  Elections can
happen at any time, but normally they are only triggered by events like a Solr instance going
down.  When documents are indexed, SolrCloud will forward them to the leader of the shard,
and the leader will distribute them to all the shard replicas.
   * '''''Replica''''': One copy of a shard.  Each replica exists within Solr as a core. 
A collection named "test" created with numShards=1 and replicationFactor set to two will have
exactly two replicas, so there will be two cores, each on a different machine (or Solr instance).
 One will be named test_shard1_replica1 and the other will be named test_shard1_replica2.
-  * '''''Shard''''': A logical piece (or slice) of a collection.  Each shard is made up of
one or more replicas.  An election is held to determine which replica is the leader.
+  * '''''Shard''''': A logical piece (or slice) of a collection.  Each shard is made up of
one or more replicas.  An election is held to determine which replica is the leader.  This
term is also in the General list below, but there it refers to Solr cores.  The SolrCloud
concept of a shard is a logical division.
   * '''''Zookeeper''''': This is a program that helps other programs keep a functional cluster
running.  SolrCloud requires [[http://zookeeper.apache.org/|Zookeeper]].  It handles leader
elections.  Although Solr can be run with an embedded Zookeeper, it is recommended that it
be standalone, installed separately from Solr.  It is also recommended that it be a redundant
ensemble, requiring at least three hosts.  Zookeeper can run on the same hardware as Solr,
and many users do run it on the same hardware.
  
  == General ==
@@ -34, +34 @@

   * '''''QTime''''': The elapsed time (in milliseconds) between the arrival of the request
(when the SolrQueryRequest object is created) and the completion of the request handler. 
It does not include time spent in the response writer formatting/streaming the response to
the client.
   * '''''Query Parser''''': A Solr component that parses the parameters and search terms
submitted in a search query.
   * '''''Searcher''''': In Solr parlance, the term "Searcher" tends to refer to an instance
of the !SolrIndexSearcher class.  This class is responsible for executing all searches done
against the index, and manages several caches.  There is typically  one Searcher per !SolrCore
at any given time, and that searcher is used to execute all queries against that !SolrCore,
but there may be additional Searchers open at a time during cache warming (in which and "old
Searcher" is still serving live requests while a "new Searcher" is being warmed up).
-  * '''''Shard''''': A distributed index is partitioned into "shards". Each shard corresponds
to a Lucene instance and contains a disjoint subset of the documents in the index.
+  * '''''Shard''''': A distributed index is partitioned into "shards". Each shard corresponds
to a Solr core and contains a disjoint subset of the documents in the index.
   * '''''Slop''''': As in "phrase slop": the number of positions two tokens need to be moved
in order to match a phrase in a query.
-  * '''''Solr Core''''': Also referred to as just a "'''''Core'''''" This is a running instance
of a Solr index along with all of its configuration (SolrConfigXml, SchemaXml, etc...).  A
single Solr application can contain 0 or more cores which are run largely in isolation but
can communicate with each other if necessary via the !CoreContainer.  From a historical perspective:
Solr initially only supported one index, and the !SolrCore class was a singleton for coordinating
the low-level functionality at the "core" of Solr.  When support was added for [[CoreAdmin|creating
and managing multiple Cores]] on the fly, the class was refactored to no longer be a Singleton,
but the name stuck.
+  * '''''Solr Core''''': Also referred to as just a "'''''Core'''''" This is a running instance
of a Lucene index along with all the Solr configuration (SolrConfigXml, SchemaXml, etc...)
required to use it.  A single Solr application can contain 0 or more cores which are run largely
in isolation but can communicate with each other if necessary via the !CoreContainer.  From
a historical perspective: Solr initially only supported one index, and the !SolrCore class
was a singleton for coordinating the low-level functionality at the "core" of Solr.  When
support was added for [[CoreAdmin|creating and managing multiple Cores]] on the fly, the class
was refactored to no longer be a Singleton, but the name stuck.
   * '''''Solr Home Dir''''': Also referred to as the "'''''Solr Home Directory'''''" or just
"'''''Solr Home'''''" this is the main directory where Solr will look for configuration files,
data, and plugins.  Knowing which directory to use as the Solr Home is the one piece of information
that Solr must either assume (the default is "./solr") or be configured using some mechanism
beyond Solr's normal configuration files.  An [[http://svn.apache.org/repos/asf/lucene/dev/trunk/solr/example/solr/|example
Solr Home]] is included in Solr releases and contains a [[http://svn.apache.org/repos/asf/lucene/dev/trunk/solr/example/solr/README.txt|README.txt]]
explaining the directory structure.  For more information on ways to override the default
Solr Home, please read SolrInstall.
   * '''''Static warming''''': What users can do using newSearcher and firstSearcher event
listeners to force explicit warming actions to be taken when one of these events happens --
frequently it involves seeding one or more caches with values from "static" queries hard coded
in the solrconfig.xml
  

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