Apache Solr Reference Guide Covering Apache Solr 6.0

Data sent to Solr is not searchable until it has been committed to the index. The reason for this is that in some
cases commits can be slow and they should be done in isolation from other possible commit requests to avoid
overwriting data. So, it's preferable to provide control over when data is committed. Several options are available
to control the timing of commits.
commit and softCommit
In Solr, a commit is an action which asks Solr to "commit" those changes to the Lucene index files. By default
commit actions result in a "hard commit" of all the Lucene index files to stable storage (disk). When a client
includes a commit=true parameter with an update request, this ensures that all index segments affected by the
adds & deletes on an update are written to disk as soon as index updates are completed.
If an additional flag softCommit=true is specified, then Solr performs a 'soft commit', meaning that Solr will
commit your changes to the Lucene data structures quickly but not guarantee that the Lucene index files are
written to stable storage. This is an implementation of Near Real Time storage, a feature that boosts document
visibility, since you don't have to wait for background merges and storage (to ZooKeeper, if using SolrCloud) to
finish before moving on to something else. A full commit means that, if a server crashes, Solr will know exactly
where your data was stored; a soft commit means that the data is stored, but the location information isn't yet
stored. The tradeoff is that a soft commit gives you faster visibility because it's not waiting for background
merges to finish.
For more information about Near Real Time operations, see Near Real Time Searching.
autoCommit
These settings control how often pending updates will be automatically pushed to the index. An alternative to au
toCommit is to use commitWithin, which can be defined when making the update request to Solr (i.e., when
pushing documents), or in an update RequestHandler.
Setting
maxDocs
maxTime
Description
The number of updates that have occurred since the last commit.
The number of milliseconds since the oldest uncommitted update.
openSearcher Whether to open a new searcher when performing a commit. If this is false, the default, the
commit will flush recent index changes to stable storage, but does not cause a new searcher
to be opened to make those changes visible
If either of these maxDocs or maxTime limits are reached, Solr automatically performs a commit operation. If the
autoCommit tag is missing, then only explicit commits will update the index. The decision whether to use
auto-commit or not depends on the needs of your application.
Determining the best auto-commit settings is a tradeoff between performance and accuracy. Settings that cause
frequent updates will improve the accuracy of searches because new content will be searchable more quickly,
but performance may suffer because of the frequent updates. Less frequent updates may improve performance
but it will take longer for updates to show up in queries.
10000
1000
false
You can also specify 'soft' autoCommits in the same way that you can specify 'soft' commits, except that instead
of using autoCommit you set the autoSoftCommit tag.
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