title: solr autoSoftCommit will open new searcher?
body: <p>this is my solrconfig.xml section:</p>
  
  <pre><code> &lt;autoCommit&gt; 
      &lt;maxTime&gt;15000&lt;/maxTime&gt; 
      &lt;openSearcher&gt;false&lt;/openSearcher&gt;
    &lt;/autoCommit&gt;
     &lt;autoSoftCommit&gt; 
      &lt;maxTime&gt;1000&lt;/maxTime&gt;
    &lt;/autoSoftCommit&gt;
  </code></pre>
  
  <p>this is test add document command:</p>
  
  <pre><code>curl http://localhost:8983/solr/AluSupply/update/json 
  -H 'Content-Type:application/json' 
  -d '[{ "CompanyRoleId": 1, 
      "Description": " hello test", 
      "CityId": 1404, 
      "CompanyId": 32733,
      "SupplyTitle": "this is title", 
      "Id":399998}]'
  </code></pre>
  
  <p>I observed autoSoftCommit, always opens a new org.apache.solr.search.SolrIndexSearcher, whether this will seriously affect the performance of it?</p>
  
  <p>this is log information:</p>
  
  <p>9117 [commitScheduler-7-thread-1] INFO  org.apache.solr.update.UpdateHandler  – start commit{,optimize=false,openSearcher=true,waitSearcher=true,expungeDeletes=false,softCommit=true,prepareCommit=false}</p>
  
  <p>9142 [commitScheduler-7-thread-1] INFO  org.apache.solr.search.SolrIndexSearcher  – Opening Searcher@648353f6 main</p>
  
  <p>9143 [commitScheduler-7-thread-1] INFO  org.apache.solr.update.UpdateHandler  – end_commit_flush</p>
  
  <p>9144 [searcherExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – QuerySenderListener sending requests to Searcher@648353f6 main{StandardDirectoryReader(segments_nf:3441:nrt _194(4.3):C2/1 _19n(4.3):C1)}</p>
  
  <p>9144 [searcherExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – QuerySenderListener done.</p>
  
  <p>9147 [searcherExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – [AluSupply] Registered new searcher Searcher@648353f6 main{StandardDirectoryReader(segments_nf:3441:nrt _194(4.3):C2/1 _19n(4.3):C1)}</p>