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Search API

Endpoint Address​

Vectara exposes a REST endpoint at the following URL to search content from a corpus:
https://api.vectara.io/v1/query

Once you've indexed data into one or more corpora, you're ready to run queries and display the results. This page provides a detailed reference guide for how to do that.

Full Definition​

The full definition of the gRPC interface is covered below.

Service​

Fundamentally, the system accepts a query and returns a response, which contains a list of results. However, for efficiency, one or more queries can be batched into a single request.

service QueryService {
  rpc Query(BatchQueryRequest) returns (BatchQueryResponse) { }
}

Query​

A single query consists of a query, which is specified in plain text. For example, "Where can I buy the latest iPhone?". Optionally, the query context provides additional information that the system may use to refine the results. For example, "The Apple store near my house is closed due to Covid."

The start field controls the starting position within the list of results, while num_results dictates how many results are returned. Thus, setting start=5 and num_results=20 would return twenty results beginning at position five. These fields are mainly used to provide pagination.

The CorpusKey specifies a list of corpora against which to run the query. While it's most often the case that a query is run against a single corpus, it's sometimes useful to run against several in parallel.

Finally, the reranking configuration enables reranking of results, to further increase relevance in certain scenarios. For details, see Reranking under the Advanced Scenarios section below.

message QueryRequest {
  string query = 5;
  string query_context = 10;

  uint32 start = 15;
  uint32 num_results = 20;
  repeated CorpusKey corpus_key = 25;

  // Configuration options for reranking.
  message RerankingConfig {
    uint32 reranker_id = 5;
  }
  RerankingConfig reranking_config = 30;
}

Corpus Key​

At the most basic level, the corpus key specifies the id of the corpus being searched. Specifying the customer_id is optional, since it defaults to the customer attached to the gRPC request.

The metadata_filter allows specifying a predicate expression that restricts the search to a part of the corpus. The filter is written in a simplified SQL dialect and can reference metadata that was marked as filterable during corpus creation. See the Filter Expressions Overview for a description of their syntax, and Corpus Administration to learn how referenceable metadata is specified during corpus creation.

If the corpus specifies custom dimensions, weights can be assigned to each dimension as well.

Finally, it's possible to override the semantic interpretation of the query string. Usually, the default settings for the corpus are sufficient. In more advanced scenarios, it's desirable to force it to be treated as a query, or, more rarely, as a response.

message CorpusKey {
  uint32 customer_id = 5;
  uint32 corpus_id = 10;

  enum Semantics {
    DEFAULT = 0;
    QUERY = 1;
    RESPONSE = 2;
  }
  Semantics semantics = 15;

  repeated CustomDimension dim = 20;
  string metadata_filter = 25;
}

Response​

The response message encapsulates a single query result. It is a subdocument provided at indexing time. The text is the subdocument text, the score indicates how well the text answers the query (higher scores are better).

The metadata list holds any subdocument-level metadata that was stored with the item at indexing time. The corpus_key indicates which corpus the result came from: recall that a single query can execute against multiple corpora.

Finally, the document_index points at a specific document within the enclosing response set's document array. This is useful for retrieving the document id and document-level metadata.

message Response {
  string text = 5;
  float score = 10;
  repeated Attribute metadata = 20;
  uint32 document_index = 25;     // Pointer to the document in the ResponseSet.
  CorpusKey corpus_key = 30;
}

ResponseSet​

The response set groups a list of responses, sorted in order of score, together with a list of statuses and enclosing documents. Since it's possible for several results to come from the same document, the length of the document list may be less than the length of the response list.

message ResponseSet {
  repeated Response response = 5;
  repeated Status status = 10;    // Potentially multiple warnings.

  message Document {
    string id = 5;
    repeated Attribute metadata = 10;
  }
  repeated Document document = 15;
}

Attribute​

Attribute represents a named piece of metadata. Both the name and its value are string typed.

message Attribute {
  string name = 5;
  string value = 10;
}

Batch Query and Response​

The batch query request and response messages simply aggregate several individual queries and response sets, respectively. The response sets will match the queries in both number and order, so, for example, the third response set in the batch response will correspond with the third query in the batch request.

message BatchQueryRequest {
  repeated QueryRequest query = 5;
}

message BatchQueryResponse {
  repeated ResponseSet response_set = 5;

  repeated Status status = 1000;
}

Advanced Scenarios​

Searching Multiple Corpora​

Sometimes, it's advantageous to search multiple corpora at the same time. In those cases, you need two things:

  1. Permissions (e.g. via an API key) that's set up to have access to all of the corpora you're interested in searching
  2. A modification to the query body as outlined below

The query body modification that's necessary is that corpusKey can take an array of objects. So if you're currently searching 1 corpus as follows:

...
"corpusKey": [
  {
    "customerId": 1234,
    "corpusId": 5678,
    "semantics": 0,
    "metadataFilter": "",
    "dim": []
  }
]
...

As long as the API key you're using has permissions to each of these corpora, you can search multiple corpora at once as follows:

...
"corpusKey": [
  {
    "customerId": 1234,
    "corpusId": 5678,
    "semantics": 0,
    "metadataFilter": "",
    "dim": []
  },
  {
    "customerId": 1234,
    "corpusId": 9876,
    "semantics": 0,
    "metadataFilter": "",
    "dim": []
  }
]
...

This then means that the query will return results across the queried corpora. The corpusKey will be returned in the response for each document if you need to use it in your application.