A field type defines the analysis that will occur on a field when documents are indexed or queries are sent to the index.
A field type definition can include four types of information:
- The name of the field type (mandatory).
- An implementation class name (mandatory).
- If the field type is
TextField, a description of the field analysis for the field type.
- Field type properties - depending on the implementation class, some properties may be mandatory.
Field Type Definitions in schema.xml
Field types are defined in
schema.xml. Each field type is defined between
fieldType elements. They can optionally be grouped within a
types element. Here is an example of a field type definition for a type called
<fieldType name="text_general" class="solr.TextField" positionIncrementGap="100"> <analyzer type="index"> <tokenizer class="solr.StandardTokenizerFactory"/> <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" /> <!-- in this example, we will only use synonyms at query time <filter class="solr.SynonymFilterFactory" synonyms="index_synonyms.txt" ignoreCase="true" expand="false"/> --> <filter class="solr.LowerCaseFilterFactory"/> </analyzer> <analyzer type="query"> <tokenizer class="solr.StandardTokenizerFactory"/> <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" /> <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" ignoreCase="true" expand="true"/> <filter class="solr.LowerCaseFilterFactory"/> </analyzer> </fieldType>
|1||The first line in the example above contains the field type name, |
|2||The rest of the definition is about field analysis, described in Understanding Analyzers, Tokenizers, and Filters.|
The implementing class is responsible for making sure the field is handled correctly. In the class names in
schema.xml, the string
solr is shorthand for
solr.TextField is really
Field Type Properties
The field type
class determines most of the behavior of a field type, but optional properties can also be defined. For example, the following definition of a date field type defines two properties,
<fieldType name="date" class="solr.DatePointField" sortMissingLast="true" omitNorms="true"/>
The properties that can be specified for a given field type fall into three major categories:
These are the general properties for fields:
- The name of the fieldType. This value gets used in field definitions, in the "type" attribute. It is strongly recommended that names consist of alphanumeric or underscore characters only and not start with a digit. This is not currently strictly enforced.
The class name that gets used to store and index the data for this type. Note that you may prefix included class names with "solr." and Solr will automatically figure out which packages to search for the class - so
If you are using a third-party class, you will probably need to have a fully qualified class name. The fully qualified equivalent for
- For multivalued fields, specifies a distance between multiple values, which prevents spurious phrase matches.
- For text fields. If
true, Solr automatically generates phrase queries for adjacent terms. If
false, terms must be enclosed in double-quotes to be treated as phrases.
Query used to combine scores of overlapping query terms (i.e., synonyms). Consider a search for "blue tee" with query-time synonyms
as_same_term(default) to blend terms, i.e.,
SynonymQuery(tshirt,tee)where each term will be treated as equally important. Use
pick_bestto select the most significant synonym when scoring
as_distinct_termsto bias scoring towards the most significant synonym
(pants OR slacks).
as_same_termis appropriate when terms are true synonyms (television, tv). Use
as_distinct_termswhen synonyms are expanding to hyponyms
(q=jeans w/ jeans=>jeans,pants)and you want exact to come before parent and sibling concepts. See this blog article.
For text fields, applicable when querying with
sow=false(which is the default for the
true, the default, for field types with query analyzers including graph-aware filters, e.g., Synonym Graph Filter and Word Delimiter Graph Filter.
falsefor field types with query analyzers including filters that can match docs when some tokens are missing, e.g., Shingle Filter.
- Defines a custom
DocValuesFormatto use for fields of this type. This requires that a schema-aware codec, such as the
SchemaCodecFactory, has been configured in
- Defines a custom
PostingsFormatto use for fields of this type. This requires that a schema-aware codec, such as the
SchemaCodecFactory, has been configured in
Lucene index back-compatibility is only supported for the default codec. If you choose to customize the
Field Default Properties
These are properties that can be specified either on the field types, or on individual fields to override the values provided by the field types.
The default values for each property depend on the underlying
FieldType class, which in turn may depend on the
version attribute of the
<schema/>. The table below includes the default value for most
FieldType implementations provided by Solr, assuming a
schema.xml that declares
|indexed||If true, the value of the field can be used in queries to retrieve matching documents.||true or false||true|
|stored||If true, the actual value of the field can be retrieved by queries.||true or false||true|
|docValues||If true, the value of the field will be put in a column-oriented DocValues structure.||true or false||false|
|sortMissingFirst sortMissingLast||Control the placement of documents when a sort field is not present.||true or false||false|
|multiValued||If true, indicates that a single document might contain multiple values for this field type.||true or false||false|
|uninvertible||If true, indicates that an ||true or false||true|
|omitNorms||If true, omits the norms associated with this field (this disables length normalization for the field, and saves some memory). Defaults to true for all primitive (non-analyzed) field types, such as int, float, data, bool, and string. Only full-text fields or fields need norms.||true or false||*|
|omitTermFreqAndPositions||If true, omits term frequency, positions, and payloads from postings for this field. This can be a performance boost for fields that don’t require that information. It also reduces the storage space required for the index. Queries that rely on position that are issued on a field with this option will silently fail to find documents. This property defaults to true for all field types that are not text fields.||true or false||*|
|omitPositions||Similar to ||true or false||*|
|termVectors termPositions termOffsets termPayloads||These options instruct Solr to maintain full term vectors for each document, optionally including position, offset and payload information for each term occurrence in those vectors. These can be used to accelerate highlighting and other ancillary functionality, but impose a substantial cost in terms of index size. They are not necessary for typical uses of Solr.||true or false||false|
|required||Instructs Solr to reject any attempts to add a document which does not have a value for this field. This property defaults to false.||true or false||false|
|useDocValuesAsStored||If the field has docValues enabled, setting this to true would allow the field to be returned as if it were a stored field (even if it has ||true or false||true|
|large||Large fields are always lazy loaded and will only take up space in the document cache if the actual value is < 512KB. This option requires ||true or false||false|
Field Type Similarity
A field type may optionally specify a
<similarity/> that will be used when scoring documents that refer to fields with this type, as long as the "global" similarity for the collection allows it.
By default, any field type which does not define a similarity, uses
BM25Similarity. For more details, and examples of configuring both global & per-type Similarities, please see Other Schema Elements.