Improve search quality

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Search quality refers to the quality of search results in terms of ranking and recall as perceived by the user making the search query.

Ranking refers to the ordering of items and recall refers to the number of relevant items retrieved. An item (also referred to as a document) is any piece of digital content that Google Cloud Search can index. Types of items include Microsoft Office documents, PDF files, a row in a database, unique URLs, and so on. An item is comprised of:

• Structured metadata
• Indexable content
• ACLs

Cloud Search uses a variety of signals to retrieve and to rank search query results; the items resulting from a search query. You can influence Cloud Search’s signals through settings in the schema, the item's content and metadata (during indexing), and the search application. The goal of this document is to help you improve search quality through modification of these signal influencers.

For a summary of recommended and optional settings, refer to Summary of recommended and optional search quality settings.

Influence topicality score

Topicality refers to the relevance of a search result to the original query terms. Topicality of an item is calculated based on the following criteria:

• The importance of each query term.
• The number of hits (the number of times a query term appears in the item’s content or metadata).
• The type of matches the query term, and their variants, have with an item indexed in Cloud Search.

To influence a text property's topicality score, define the RetrievalImportance on the text property in your schema. A match on a property with high RetrievalImportance results in a higher score compared to a match on a property with low RetrievalImportance.

For example, suppose you have a data source with the following characteristics:

• The data source is used to store history for software bugs.
• Each bug has a name, description, and priority.

Most users would query this data source using the bug name, so you would set the RetrievalImportance on the name to HIGHEST in the schema.

Conversely, most users may not query this data source using the description of the bug, so, set the RetrievalImportance on the description to DEFAULT. Following is sample schema containing RetrievalImportance settings.

{
  "objectDefinitions": [
    {
      "name": "issues",
      "propertyDefinitions": [
        {
          "name": "summary",
          "textPropertyOptions": {
            "retrievalImportance": {
              "importance": HIGHEST
              }
            }
          },
        {
          "name": "description",
          "textPropertyOptions": {
            "retrievalImportance": {
              "importance": DEFAULT
              }
            }
          },
        {
          "name": "label",
            "isRepeatable": true,
          "textPropertyOptions": {
            "retrievalImportance": {
              "importance": DEFAULT
              }
            }
          },
        {
          "name": "comments",
          "textPropertyOptions": {
            "retrievalImportance": {
              "importance": DEFAULT
              }
            }
          },
        {
          "name": "project",
          "textPropertyOptions": {
            "retrievalImportance": {
              "importance": HIGH
              }
            }
          },
        {
          "name": "duedate",
          "datePropertyOptions": {
          }
        },
        ...
      ]
    }
  ]
}

In the case of HTML documents, tags such as