Configuration

An index can be configured in many ways including different configurations per field such as how those values are analyzed, indexed, tokenized ... basically how the data is stored and retrieved. This is done via Examine "Value Types".

Note: This documentation refers to using Lucene based indexes in Examine (the default index type shipped in Examine).

Field definitions

A Field Definition is a mapping of a field name to a "Value Types". By default all fields are mapped to the default Value Type: FieldDefinitionTypes.FullText.

You can map a field to any value type when configuring the index.

IConfigureNamedOptions

Configuration of Examine indexes is done with .NET's Options pattern. For Examine, this is done with named options: IConfigureNamedOptions.

There are several options that can be configured, the most common ones are:

FieldDefinitions FieldDefinitionCollection - Manages the mappings between a field name and it's index value type
Analyzer Analyzer - The default Lucene Analyzer to use for each field (default = StandardAnalyzer)
Validator IValueSetValidator - Used to validate a value set to be indexed, if validation fails it will not be indexed
IndexValueTypesFactory IReadOnlyDictionary<string, IFieldValueTypeFactory> - Allows you to define custom Value Types

/// <summary>
/// Configure Examine indexes using .NET IOptions
/// </summary>
public sealed class ConfigureIndexOptions : IConfigureNamedOptions<LuceneDirectoryIndexOptions>
{
    public void Configure(string name, LuceneDirectoryIndexOptions options)
    {
        switch (name)
        {
            case "MyIndex":
                // Set the "Price" field to map to the 'Double' value type.
                options.FieldDefinitions.AddOrUpdate(
                    new FieldDefinition("Price", FieldDefinitionTypes.Double));
                break;
        }
    }

    public void Configure(LuceneDirectoryIndexOptions options) 
        => Configure(string.Empty, options);
}

Value types

Value types are responsible for:

Defining a field name and if the field should be sortable, the field to store the sortable data
Adding a field value to an index document
Configuring how the value will be stored in the index
Configuring the analyzer for the field
Generating the Query for the field

These are the default field value types provided with Examine. Each value type can be resolved from the static class Examine.FieldDefinitionTypes (i.e. Examine.FieldDefinitionTypes.FullText).

Value Type	Description	Sortable	Facetable	Retrievable	Searchable	Filterable	Analyzer
FullText	Default. The field will be indexed with the index's default Analyzer without any sortability. Generally this is fine for normal text searching.	❌	❌	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
FullTextSortable	Will be indexed with FullText but also enable sorting on this field for search results. FullText sortability adds additional overhead since it requires an additional index field.	✅	❌	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
Integer	Stored as a numerical structure.	✅	❌	✅	❌	✅	-
Float	Stored as a numerical structure.	✅	❌	✅	❌	✅	-
Double	Stored as a numerical structure.	✅	❌	✅	❌	✅	-
Long	Stored as a numerical structure.	✅	❌	✅	❌	✅	-
DateTime	Stored as a DateTime, represented by a numerical structure.	✅	❌	✅	❌	✅	-
DateYear	Just like DateTime but with precision only to the year.	✅	❌	✅	❌	✅	-
DateMonth	Just like DateTime but with precision only to the month.	✅	❌	✅	❌	✅	-
DateDay	Just like DateTime but with precision only to the day.	✅	❌	✅	❌	✅	-
DateHour	Just like DateTime but with precision only to the hour.	✅	❌	✅	❌	✅	-
DateMinute	Just like DateTime but with precision only to the minute.	✅	❌	✅	❌	✅	-
EmailAddress	Uses custom analyzers for dealing with email address searching.	❌	❌	✅	✅	✅	EmailAddressAnalyzer
InvariantCultureIgnoreCase	Uses custom analyzers for dealing with text so it can be searched on regardless of the culture/casing.	❌	❌	✅	✅	✅	CultureInvariantStandardAnalyzer
Raw	Will be indexed without analysis, searching will only match with an exact value.	❌	❌	✅	✅	✅	KeywordAnalyzer
FacetFullText	The field will be indexed with the index's default Analyzer without any sortability. Generally this is fine for normal text searching.	❌	✅	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
FacetFullTextSortable	Will be indexed with FullText but also enable sorting on this field for search results. FullText sortability adds additional overhead since it requires an additional index field.	✅	✅	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
FacetInteger	Stored as a numerical structure.	✅	✅	✅	❌	✅	-
FacetFloat	Stored as a numerical structure.	✅	✅	✅	❌	✅	-
FacetDouble	Stored as a numerical structure.	✅	✅	✅	❌	✅	-
FacetLong	Stored as a numerical structure.	✅	✅	✅	❌	✅	-
FacetDateTime	Stored as a DateTime, represented by a numerical structure.	✅	✅	✅	❌	✅	-
FacetDateYear	Just like DateTime but with precision only to the year.	✅	✅	✅	❌	✅	-
FacetDateMonth	Just like DateTime but with precision only to the month.	✅	✅	✅	❌	✅	-
FacetDateDay	Just like DateTime but with precision only to the day.	✅	✅	✅	❌	✅	-
FacetDateHour	Just like DateTime but with precision only to the hour.	✅	✅	✅	❌	✅	-
FacetDateMinute	Just like DateTime but with precision only to the minute.	✅	✅	✅	❌	✅	-
FacetTaxonomyFullText	The field will be indexed with the index's default Analyzer without any sortability. Generally this is fine for normal text searching. Stored in the Taxonomy Facet sidecar index.	❌	✅	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
FacetTaxonomyFullTextSortable	Will be indexed with FullText but also enable sorting on this field for search results. FullText sortability adds additional overhead since it requires an additional index field. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	✅	✅	CultureInvariantStandardAnalyzer or Index default
FacetTaxonomyInteger	Stored as a numerical structure. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyFloat	Stored as a numerical structure. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDouble	Stored as a numerical structure. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyLong	Stored as a numerical structure. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateTime	Stored as a DateTime, represented by a numerical structure. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateYear	Just like DateTime but with precision only to the year. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateMonth	Just like DateTime but with precision only to the month. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateDay	Just like DateTime but with precision only to the day. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateHour	Just like DateTime but with precision only to the hour. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-
FacetTaxonomyDateMinute	Just like DateTime but with precision only to the minute. Stored in the Taxonomy Facet sidecar index.	✅	✅	✅	❌	✅	-

Custom field value types

A field value type is defined by IIndexFieldValueType

Tip: There are many implementations of IIndexFieldValueType in the source code to use as examples/reference.

A common base class that can be used for field value types is: IndexFieldValueTypeBase.

A common implementation that can be used for field value types for custom Analyzers is: GenericAnalyzerFieldValueType.

Example - Phone Number

A phone number stored in Lucene could require a custom analyzer to index and search it properly. So the best way to set this up in Examine would be to have a custom field value type for it. Since this field value type doesn't need to do anything more fancy than to provide a custom analyzer, we can create it with the GenericAnalyzerFieldValueType.

/// <summary>
/// Configure Examine indexes using .NET IOptions
/// </summary>
public sealed class ConfigureIndexOptions : IConfigureNamedOptions<LuceneDirectoryIndexOptions>
{
    private readonly ILoggerFactory _loggerFactory;

    public ConfigureIndexOptions(ILoggerFactory loggerFactory)
        => _loggerFactory = loggerFactory;

    public void Configure(string name, LuceneDirectoryIndexOptions options)
    {
        switch (name)
        {
            case "MyIndex":
                // Create a dictionary for custom value types.
                // They keys are the value type names.
                options.IndexValueTypesFactory = new Dictionary<string, IFieldValueTypeFactory>
                {
                    // Create a phone number value type using the GenericAnalyzerFieldValueType
                    // to pass in a custom analyzer. As an example, it could use Examine's
                    // PatternAnalyzer to pass in a phone number pattern to match.
                    ["phone"] = new DelegateFieldValueTypeFactory(name =>
                                    new GenericAnalyzerFieldValueType(
                                        name,
                                        _loggerFactory,
                                        new PatternAnalyzer(@"\d{3}\s\d{3}\s\d{4}", 0)))
                };

                // Add the field definition for a field called "phone" which maps
                // to a Value Type called "phone" defined above.
                options.FieldDefinitions.AddOrUpdate(new FieldDefinition("phone", "phone"));
                break;
        }
    }

    public void Configure(LuceneDirectoryIndexOptions options)
        => throw new NotImplementedException("This is never called and is just part of the interface");
}

The above creates a custom field value type using a custom analyzer and maps the "Phone" field to use this value type.

ValueSet validators

An IValueSetValidator is a simple interface:

public interface IValueSetValidator
{
    ValueSetValidationResult Validate(ValueSet valueSet);
}

That returns an result ValueSetValidationResult with an enum of ValueSetValidationStatus values:

Valid - The ValueSet is valid and will be indexed
Failed - The ValueSet was invalid and will not be indexed
Filtered - The ValueSet has been filtered/modified by the validator and will be indexed

Examine only has one implementation: ValueSetValidatorDelegate which can be used by developers as a simple way to create a validator based on a callback, else developers can implement this interface if required. By default, no ValueSet validation is done with Examine.

When using the facets feature it's possible to add facets configuration to change the behavior of the indexing.

For example, you can allow multiple values in an indexed field with the configuration below.

// Create a config
var facetsConfig = new FacetsConfig();

// Set field to be able to contain multiple values (This is default for a field in Examine. But you only need this if you are actually using multiple values for a single field)
facetsConfig.SetMultiValued("MultiIdField", true);

services.AddExamineLuceneIndex("MyIndex",
    // Set the indexing of your fields to use the facet type
    fieldDefinitions: new FieldDefinitionCollection(
        new FieldDefinition("Timestamp", FieldDefinitionTypes.FacetDateTime),

        new FieldDefinition("MultiIdField", FieldDefinitionTypes.FacetFullText)
        ),
    // Pass your config
    facetsConfig: facetsConfig
    );

Without this configuration for multiple values, you'll notice that your faceted search breaks or behaves differently than expected.

To enable support for hierarchical facets as well as supporting faster faceting the Taxonomy Facet sidecar index can be enabled.

Set LuceneIndexOptions.UseTaxonomyIndex = true; for the index. This enables the use of the Taxonomy sidecar index.
Change the Field Definitions to use the "FacetTaxonomy" Field Definition Types instead of the "Facet" types. E.g. FieldDefinitionTypes.FacetFullText => FieldDefinitionTypes.FacetTaxonomyFullText.
To enable hierarchical facets on a field, call FacetsConfig.SetHierarchical("facetfieldname", true);

Example:

// Create a config
var facetsConfig = new FacetsConfig();

// Set field to be able to support hierarchical facets
facetsConfig.SetHierarchical("hierarchyFacetfield", true);

// Set field to be able to contain multiple values (This is default for a field in Examine. But you only need this if you are actually using multiple values for a single field)
facetsConfig.SetMultiValued("MultiIdField", true);

services.AddExamineLuceneIndex("MyIndex",
    // Set the indexing of your fields to use the facet Taxonomy type
    fieldDefinitions: new FieldDefinitionCollection(
        new FieldDefinition("Timestamp", FieldDefinitionTypes.FacetTaxonomyDateTime),
        new FieldDefinition("hierarchyFacetfield", FieldDefinitionTypes.FacetTaxonomyFullText),

        new FieldDefinition("MultiIdField", FieldDefinitionTypes.FacetTaxonomyFullText)
        ),
    // Pass your config
    facetsConfig: facetsConfig,
    // Enable the Taxonomy sidecar index
    useTaxonomyIndex: true
    );

Note: See more examples of how facets configuration can be used under Searching

To explore other configuration settings see the links below:

FacetsConfig API docs
Facets with lucene. See how the config is used in the code examples.

Luke

Lucene.NET 4.8 is compatible with Java Luke 4.8.0, a useful tool for working with Lucene Indexes. Newer versions of Luke can't be used with Lucene.NET 4.8 indexes. Luke 4.8.0

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