Query expansion

Query expansion is the incremental loosening of query constraints to include more results when none or too few are initially found. This leads to an adjustment of the result size per query.

When there are no relevant documents at all for a query, Query expansion will return less relevant documents to ensure that query does not return zero search results.

Query expansion tutorial

This tutorial shows you how to enable the query expansion feature. When a shopper uses an ambiguous or a multi-word search phrase, they can get an empty response. After turning on query expansion, the request is analyzed and the expanded list of products based on the parsed search query gets returned.

To follow step-by-step guidance for this task directly in the Cloud Shell Editor, click Guide me :

Guide me

Example dataset

This page uses the following dataset as an example. Expand it to view the fields within the sample product description dataset.

Query expansion

Query expansion increases the recall for query terms with few results, especially long tail queries.

This search feature is driven by a specification determining query-expansion conditions. It includes a pinUnexpandedResults option that's off by default. When set to true , it displays unexpanded products at the top of search results. The top is followed by the expanded results.

  import 
  
 com.google.cloud.retail.v2. SearchRequest 
 
 ; 
 import 
  
 com.google.cloud.retail.v2. SearchRequest 
. QueryExpansionSpec 
 
 ; 
 import 
  
 com.google.cloud.retail.v2. SearchRequest 
. QueryExpansionSpec 
. Condition 
 
 ; 
 import 
  
 com.google.cloud.retail.v2. SearchResponse 
 
 ; 
 import 
  
 com.google.cloud.retail.v2. SearchServiceClient 
 
 ; 
 public 
  
 static 
  
 void 
  
 searchProductsWithQueryExpansion 
 ( 
 String 
  
 query 
 , 
  
 int 
  
 pageSize 
 , 
  
  Condition 
 
  
 condition 
 ) 
  
 throws 
  
 IOException 
 , 
  
 InterruptedException 
  
 { 
  
  QueryExpansionSpec 
 
  
 queryExpansionSpec 
  
 = 
  
  QueryExpansionSpec 
 
 . 
 newBuilder 
 () 
  
 . 
 setCondition 
 ( 
 condition 
 ) 
  
 . 
 build 
 (); 
  
  SearchRequest 
 
  
 searchRequest 
  
 = 
  
  SearchRequest 
 
 . 
 newBuilder 
 () 
  
 . 
 setPlacement 
 ( 
 DEFAULT_SEARCH_PLACEMENT_NAME 
 ) 
  
 . 
 setBranch 
 ( 
 DEFAULT_BRANCH_NAME 
 ) 
  
 . 
 setVisitorId 
 ( 
 VISITOR_ID 
 ) 
  
 . 
 setQuery 
 ( 
 query 
 ) 
  
 . 
 setPageSize 
 ( 
 pageSize 
 ) 
  
 . 
  setQueryExpansionSpec 
 
 ( 
 queryExpansionSpec 
 ) 
  
 . 
 build 
 (); 
  
 try 
  
 ( 
  SearchServiceClient 
 
  
 searchClient 
  
 = 
  
  SearchServiceClient 
 
 . 
 create 
 ()) 
  
 { 
  
  SearchResponse 
 
  
 response 
  
 = 
  
 searchClient 
 . 
 search 
 ( 
 searchRequest 
 ). 
 getPage 
 (). 
 getResponse 
 (); 
  
 System 
 . 
 out 
 . 
 println 
 ( 
 "Search response: " 
  
 + 
  
 searchResponse 
 ); 
  
 } 
 } 
 

For example, if you search for Google Pixel 5 without query expansion, the result will be restricted to google_pixel_5 IDs. However, with query expansion, you might also get google_pixel_4a_with_5g , google_pixel_4a , and google_pixel_5_case IDs in the example product description dataset as well.