Solr's configuration files are extremely well documented. We're not going to go over the details here but this should give you a sense of what is where.

The schema (defined in schema.xml) contains field type definitions (defined within the <types> tag) and lists the fields that make up your schema (within the <fields> tag), which references a type. The schema contains other information too such as the primary key (the field that uniquely identifies each document—a constraint that Solr enforces) and the default search field. The sample schema in Solr uses the field named text, confusingly, there is a field type named text too. But remember that the monitor.xml document we reviewed earlier had no field named text, right? It is common for the schema to call out for certain fields to be copied to other fields—particularly fields not in input documents. So, even though the input documents don't have a field named text, there are <copyField> tags in the schema, which call for the fields named cat, name, manu, features, and includes to be copied to text. This is a popular technique to speed up queries, so that queries can search over a small number of fields rather than a long list of them. Such fields used this way are rarely stored, as they are just needed for querying and so are indexed. There is a lot more we could talk about in the schema, but we're going to move on for now.

Solr's solrconfig.xml file contains lots of parameters that can be tweaked. At the moment, we're just going to take a peak at the request handlers that are defined with <requestHandler> tags. They make up about half of the file. In our first query, we didn't specify any request handler, so we got the default one. It's defined here:

<requestHandler name="standard" class="solr.SearchHandler" default="true">
<!-- default values for query parameters -->
  <lst name="defaults">
    <str name="echoParams">explicit</str>
    <!-- 
    <int name="rows">10</int>
    <str name="fl">*</str>
    <str name="version">2.1</str>
    -->
  </lst>
</requestHandler>

When you POST commands to Solr (such as to index a document) or query Solr (HTTP GET), it goes through a particular request handler. Handlers can be registered against certain URL paths. When we uploaded the documents earlier, it went to the handler defined like this:

<requestHandler name="/update" class="solr.XmlUpdateRequestHandler" />

The request handlers oriented to querying using the class solr.SearchHandler are much more interesting.

The standard request handler defined previously doesn't really define any defaults other than the parameters that are to be echoed in the response. Remember its presence at the top of the XML output? By changing explicit to none you can have it omitted, or use all and you'll potentially see more parameters, if other defaults happened to be configured in the request handler. This parameter can alternatively be specified in the URL through echoParams=none. Remember to separate URL parameters with ampersands.