You can use the collapse (distinct) feature to collapse the result set based on a specified column when the results of a query contain large amounts of data of a specific type. Data of the specific type is displayed only once in the query results to ensure diversity of the result types.

Prerequisites

  • A Tablestore client is initialized. For more information, see Initialization.
  • A data table is created. Data is written to the table.
  • A search index is created for the data table. For more information, see Create search indexes.

Usage notes

  • If you use the collapse (distinct) feature, you can perform pagination only by specifying offset and limit instead of token.
  • If you aggregate and collapse a result set at the same time, the result set is aggregated before it is collapsed.
  • If you collapse the query results, the total number of results that are returned is determined by the sum of the offset and limit values. A maximum of 50,000 results can be returned.
  • The total number of rows in the response indicates the number of rows that meet the query conditions before you use the collapse (distinct) feature. After the result set is collapsed, the total number of distinct values cannot be queried.

Parameters

ParameterDescription
queryThe query type. You can set this parameter to any query type.
collapseThe collapse parameter, including the fieldName field.

fieldName: the name of the column based on which the result set is collapsed. Only columns whose values are of the INTEGER, FLOATING-POINT, or KEYWORD type are supported.

offsetThe position from which the current query starts.
limitThe maximum number of rows that you want the current query to return.

To query only the number of rows that meet the query conditions without returning specific data, you can set limit to 0. This way, Tablestore returns the number of rows that meet the query conditions without specific data from the table.

getTotalCountSpecifies whether to return the total number of rows that meet the query conditions. The default value of this parameter is false, which specifies that the total number of rows that meet the query conditions is not returned.

If you set this parameter to true, the query performance is compromised.

tableNameThe name of the data table.
indexNameThe name of the search index.
columnsToGetSpecifies whether to return all columns of each row that meets the query conditions.
  • If you set returnType to TableStore.ColumnReturnType.RETURN_SPECIFIED, you need to configure returnNames to specify the columns that you want to return.
  • If you set the returnType parameter to TableStore.ColumnReturnType.RETURN_ALL, all columns are returned.
  • If you set the returnType parameter to TableStore.ColumnReturnType.RETURN_ALL_FROM_INDEX, all columns in the search index are returned. .
  • If you set the returnType parameter to TableStore.ColumnReturnType.RETURN_NONE, only the primary key columns are returned.

Sample code

let searchQuery = {
    offset: 0,
    limit: 100,
    query: {
        queryType: TableStore.QueryType.MATCH_ALL_QUERY,
    },
    collapse: {
        fieldName: "col_keyword",
    },
    getTotalCount: false,
};
let params = {
    tableName: tableName,
    indexName: indexName,
    searchQuery: searchQuery,
    columnToGet: { // Specify the columns that you want to return. You can configure the RETURN_SPECIFIED parameter to return specified columns, the RETURN_ALL parameter to return all columns, the RETURN_ALL_FROM_INDEX parameter to return all columns in the search index, or the RETURN_NONE parameter to return only the primary key columns. 
        returnType: TableStore.ColumnReturnType.RETURN_ALL_FROM_INDEX
    },
    timeoutMs: 30000,
}
client.search(params, function (err, data) {
    if (err) {
        console.log('search error:', err.toString());
    } else {
        console.log('search success:', data);
    }
});