Tablestore:Collapse (distinct)

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 data tables and Write data.

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

Usage notes

• If you use the collapse (distinct) feature, you can perform pagination only by specifying the offset and limit parameters.

• 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 results of a query, the total number of results that are returned is determined by the sum of the values of the offset and limit parameters. 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

Examples

The following sample code provides an example on how to use match all query to query the total number of rows in a table and collapse the result set based on the value of the col_keyword column:

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 set the parameter to RETURN_SPECIFIED to return the specified columns, RETURN_ALL to return all columns, RETURN_ALL_FROM_INDEX to return all columns in the search index, or RETURN_NONE 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);
    }
});

FAQ

• What do I do if no data can be found by calling the Search operation?

• How do I increase the value of the limit parameter to 1000 when I call the Search operation of the search index feature to query data?

• Why does a token become invalid when pagination is used in a search index-based query?

References

• The following query types are supported by search indexes: term query, terms query, match all query, match query, match phrase query, prefix query, range query, wildcard query, Boolean query, geo query, nested query, vector query, and exists query. You can select a query type to query data based on your business requirements.

  If you want to sort or paginate the rows that meet the query conditions, you can use the sorting and paging feature. For more information, see Sorting and paging.

  If you want to collapse the result set based on a specific column, you can use the collapse (distinct) feature. This way, data of the specified type appears only once in the query results. For more information, see Collapse (distinct).

• If you want to analyze data in a data table, such as obtaining the extreme values, sum, and total number of rows, you can perform aggregation operations or execute SQL statements. For more information, see Aggregation and SQL query.

• If you want to quickly obtain all rows that meet the query conditions without the need to sort the rows, you can call the ParallelScan and ComputeSplits operations to use the parallel scan feature. For more information, see Parallel scan.