Full Text Search (FTS) Using the .NET SDK with Couchbase Server

how-to

You can use the Full Text Search service (FTS) to create queryable full-text indexes in Couchbase Server.

Full Text Search or FTS allows you to create, manage, and query full text indexes on JSON documents stored in Couchbase buckets. It uses natural language processing for querying documents, provides relevance scoring on the results of your queries, and has fast indexes for querying a wide range of possible text searches. Some of the supported query types include simple queries like Match and Term queries; range queries like Date Range and Numeric Range; and compound queries for conjunctions, disjunctions, and/or boolean queries. The .NET SDK exposes an API for performing FTS queries which abstracts some of the complexity of using the underlying REST API.

Examples

Search queries are executed at Cluster level (not bucket or collection). Here is a simple MatchQuery that looks for the text “swanky” using a defined index:

var result = cluster.SearchQuery(
    "travel-sample-index-hotel-description",
    new MatchQuery("swanky"),
    options => {
        options.WithLimit(10);
    }
);

All simple query types are created in the same manner, some have additional properties, which can be seen in common query type descriptions. Couchbase FTS’s range of query types enable powerful searching using multiple options, to ensure results are just within the range wanted. Here is a date range query that looks for dates between 1st January 2021 and 31st January:

var result = cluster.SearchQuery(
    "index-name",
    new DateRangeQuery()
        .Start(DateTime.Parse("2021-01-01"), true) // final parameter is if the range is inclusive
        .End(DateTime.Parse("2021-02-01"), false),
    options => options.Limit(10)
);

A conjunction query contains multiple child queries; its result documents must satisfy all of the child queries:

var result = cluster.SearchQuery(
    "index-name",
    new ConjunctionQuery(
        new DateRangeQuery()
            .Start(DateTime.Parse("2021-01-01"), true)
            .Start(DateTime.Parse("2021-02-01"), false),
        new MatchQuery("Swanky")
);

Working with Results

The result of a search query has three components: hits, facets, and metdata. Hits are the documents that match the query. Facets allow the aggregation of information collected on a particular result set. Metdata holds additional information not directly related to your query, such as success total hits and how long the query took to execute in the cluster.

Iterating hits

foreach (var hit in result.Hits)
{
    string documentId = hit.Id;
    double score = hit.Score;
    ...
}

Iterating facets

foreach (var facet in result.Facets)
{
    var name = facet.Name;
    var total = facet.Total;
    ...
}

Consistency

Like the Couchbase Query Service, FTS allows RequestPlus queries — Read-Your-Own_Writes (RYOW) consistency, ensuring results contain information from updated indexes:

var result = cluster.SearchQuery(
    "travel-sample-index-hotel-description",
    new MatchQuery("swanky"),
    options => {
        options.WithConsistency(ScanConsistency.RequestPlus);
    }
);