Tablestore:Highlight the query results

Prerequisites

• An OTSClient instance is initialized. For more information, see Initialize an OTSClient instance.

• A data table is created and data is written to the data table. For more information, see Create a data table and Write data.

• A search index is created for the data table. For more information, see Create search indexes.

Usage notes

• If you enable the highlight feature in a match query or match phrase query, the query strings in the query results may be highlighted by using multiple opening tags (preTag) and closing tags (postTag).

• If the tokenization method of a Text field is maximum semantic unit-based tokenization (MaxWord), the highlight feature is not supported when you perform a match phrase query on the Text field.

• If you want to return multiple fragments, the query strings in the fragments may be split. In this case, the query strings may not be highlighted.

Parameters

Example

The following sample code provides an example on how to use the MatchQuery feature to query data that matches hangzhou shanghai from the Col_Text field and highlight the keywords in the query results. In this example, the Col_Text field is of the Text type.

func MatchQuerywithHighlight(client *tablestore.TableStoreClient, tableName string, indexName string) {
    searchRequest := &tablestore.SearchRequest{}
    searchRequest.SetTableName(tableName)
    searchRequest.SetIndexName(indexName)
    query := &search.MatchQuery{} // Set the query type to MatchQuery. 
    query.FieldName = "Col_Text"  // Specify the field that you want to match. 
    query.Text = "hangzhou shanghai"  // Specify the keyword that you want to match. 
    searchQuery := search.NewSearchQuery()
    searchQuery.SetQuery(query)
    highlight := &search.Highlight{
        FieldHighlightParameters: map[string]*search.HighlightParameter{
            "Col_Text": {
                NumberOfFragments: proto.Int32(5),
                PreTag:            proto.String("<b>"),
                PostTag:           proto.String("</b>"),
            },
        },
    }
    searchQuery.SetHighlight(highlight)
    searchQuery.SetGetTotalCount(true)
    searchQuery.SetOffset(0) // Set the Offset parameter to 0. 
    searchQuery.SetLimit(20) // Set the Limit parameter to 20, which specifies that up to 20 rows can be returned. 
    searchRequest.SetSearchQuery(searchQuery)
    // Specify that all fields in the search index are returned. 
    searchRequest.SetColumnsToGet(&tablestore.ColumnsToGet{
        ReturnAllFromIndex: true,
    })

    if resp, err := client.Search(searchRequest); err != nil {
        fmt.Println("Highlighting query failed with err: ", err)
    } else {
        fmt.Println("RequestId: " + resp.RequestId)
        // Display the highlighted query results. When you query a non-Nested field, you can set the padding parameter to null. 
        printSearchHit(resp.SearchHits, " ")
    }
    fmt.Println("highlight query finished")
}

/**
 * Display the content that meets the query conditions. 
 * @param searchHits searchHits
 * If the output uses the @param prefix Nested structure, add the prefix to display the hierarchy information. 
 */
func printSearchHit(searchHits []*tablestore.SearchHit, padding string) {
    for _, searchHit := range searchHits {
        if searchHit.Score != nil {
            fmt.Printf("%sScore: %f\n", padding, *searchHit.Score)
        }

        if searchHit.Row != nil {
            jsonBody, err := json.Marshal(*searchHit.Row)
            if err != nil {
                panic(err)
            }
            fmt.Println("Row: ", string(jsonBody))
        }

        if searchHit.HighlightResultItem != nil && len(searchHit.HighlightResultItem.HighlightFields) != 0 {
            fmt.Printf("%sHighlight: \n", padding)
            for colName, highlightResult := range searchHit.HighlightResultItem.HighlightFields {
                fmt.Printf("%sColumnName: %s, Highlight_Fragments: %v\n", padding+padding, colName, highlightResult.Fragments)
            }
        }

        fmt.Println("")
    }
}

References

• For information about the highlight feature, see Highlight keywords.

• For information about how to use the highlight feature when you query Nested fields, see Nested query.