Constant score query

Query request

request is of the tablestore.SearchRequest type and contains the following parameters.

Query configuration

Create a query configuration by calling search.NewSearchQuery() and configure it by using the following methods.

Query condition

The query is of the search.ConstScoreQuery type and contains the following parameter.

Columns to return

request.ColumnsToGet is of the tablestore.ColumnsToGet type and contains the following parameters.

Combine with a Boolean query

Add a constant score query to BoolQuery.MustQueries to make the subquery contribute the fixed relevance score 1.0 to each hit. Other subqueries calculate relevance scores based on their own rules. The final score is the sum of the subquery scores.

query := &search.BoolQuery{
    MustQueries: []search.Query{
        &search.ConstScoreQuery{
            Filter: &search.MatchQuery{
                FieldName: "title",
                Text:      "go",
            },
        },
        &search.MatchQuery{
            FieldName: "title",
            Text:      "guide",
        },
    },
}
searchQuery := search.NewSearchQuery().
    SetQuery(query).
    SetLimit(10).
    SetSort(&search.Sort{Sorters: []search.Sorter{search.NewScoreSort()}})

response, err := client.Search(&tablestore.SearchRequest{
    TableName:   "example_table",
    IndexName:   "example_index",
    SearchQuery: searchQuery,
})
if err != nil {
    log.Fatal(err)
}

for _, hit := range response.SearchHits {
    fmt.Println(hit.Row, *hit.Score)
}

Use with parallel scan

If parallel scan does not need to sort rows by relevance score, wrap the filter condition in a constant score query so that the scan checks only whether rows match and does not calculate BM25 or other relevance scores for the subquery. The following example sets a constant score query as the ScanQuery condition for one worker. For the complete worker and pagination workflow, see Parallel scan.

query := &search.ConstScoreQuery{
    Filter: &search.MatchQuery{
        FieldName: "title",
        Text:      "go",
    },
}

splits, err := client.ComputeSplits(
    (&tablestore.ComputeSplitsRequest{}).
        SetTableName("example_table").
        SetSearchIndexSplitsOptions(tablestore.SearchIndexSplitsOptions{
            IndexName: "example_index",
        }),
)
if err != nil {
    log.Fatal(err)
}

scanQuery := search.NewScanQuery().
    SetQuery(query).
    SetLimit(1000).
    SetMaxParallel(splits.SplitsSize).
    SetCurrentParallelID(0)
request := (&tablestore.ParallelScanRequest{}).
    SetTableName("example_table").
    SetIndexName("example_index").
    SetScanQuery(scanQuery).
    SetSessionId(splits.SessionId).
    SetColumnsToGet(&tablestore.ColumnsToGet{
        ReturnAllFromIndex: true,
    })

response, err := client.ParallelScan(request)
if err != nil {
    log.Fatal(err)
}

fmt.Println(response.Rows)