Query the total number of rows in a table or return multiple random rows - Tablestore

You can use match all query to match all rows in a table to query the total number of rows in the table or return multiple random rows.

API operation

You can call the Search or ParallelScan operation and set the query type to MatchAllQuery to perform a match all query.

Parameters

Parameter	Description
query	The type of the query. Set the query parameter to MatchAllQuery.
tableName	The name of the data table.
indexName	The name of the search index.
limit	The maximum number of rows that you want the current query to return. If you want the current query to return multiple random rows of data, set the limit parameter to a positive integer. To query only the number of rows that meet the query conditions without specific data, set the limit parameter to 0.
columnsToGet	Specifies whether to return all columns of each row that meets the query conditions. You can specify the returnAll and columns fields for the columnsToGet parameter. The default value of the returnAll field is false, which specifies that not all columns are returned. In this case, you can use the columns field to specify the columns that you want to return. If you do not specify the columns that you want to return, only the primary key columns are returned. If you set the returnAll field to true, all columns are returned.
getTotalCount	Specifies 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.

Methods

You can use the Tablestore CLI or Tablestore SDKs to perform a match all query. Before you perform a match all query, make sure that the following preparations are made:

You have an Alibaba Cloud account or a RAM user that has permissions to perform operations on Tablestore. For information about how to grant Tablestore operation permissions to a RAM user, see Use a RAM policy to grant permissions to a RAM user.
If you want to use Tablestore SDKs or the Tablestore CLI to perform a query, an AccessKey pair is created for your Alibaba Cloud account or RAM user. For more information, see Create an AccessKey pair.
A data table is created. For more information, see Operations on tables.
A search index is created for the data table. For more information, see Create a search index.
If you want to use Tablestore SDKs to perform a query, an OTSClient instance is initialized. For more information, see Initialize an OTSClient instance.
If you want to use the Tablestore CLI to perform a query, the Tablestore CLI is downloaded and started, and information about the instance that you want to access and the data table are configured. For more information, see Download the Tablestore CLI, Start the Tablestore CLI and configure access information, and Operations on data tables.

Use the Tablestore CLI

You can use the Tablestore CLI to run the search command to query data by using search indexes. For more information, see Search index.

Run the search command to use the search_index search index to query data and return all indexed columns of each row that meets the query conditions.
```
search -n search_index --return_all_indexed
```

Enter the query conditions as prompted:

{
    "Offset": -1,
    "Limit": 10,
    "Collapse": null,
    "Sort": null,
    "GetTotalCount": true,
    "Token": null,
    "Query": {
        "Name": "MatchAllQuery",
        "Query": {
        }
    }
}

Use Tablestore SDKs

You can perform a match all query by using the following Tablestore SDKs: Tablestore SDK for Java, Tablestore SDK for Go, Tablestore SDK for Python, Tablestore SDK for Node.js, Tablestore SDK for .NET, and Tablestore SDK for PHP. In this example, Tablestore SDK for Java is used.

The following sample code provides an example on how to query the total number of rows in a table:

/**
 * Use the match all query feature to query the total number of rows in a table. 
 * @param client
 */
private static void matchAllQuery(SyncClient client) {
    SearchQuery searchQuery = new SearchQuery();

    /**
    * Set the query type to MatchAllQuery. 
    */
    searchQuery.setQuery(new MatchAllQuery()); 

    /**
     * In the MatchAllQuery-based query result, the value of TotalCount is the total number of rows in the table. 
     * If you want the current query to return multiple random rows of data, set the limit parameter to a positive integer. 
     * To query only the number of rows that meet the query conditions without querying specific data of the rows, set the limit parameter to 0. 
     */
    searchQuery.setLimit(0);
    SearchRequest searchRequest = new SearchRequest("<TABLE_NAME>", "<SEARCH_INDEX_NAME>", searchQuery);

    /**
    * Specify that the total number of rows that meet the query conditions is returned. 
    */ 
    searchQuery.setGetTotalCount(true);
    SearchResponse resp = client.search(searchRequest);
    /**
     * Check whether the returned total number of rows that meet the query conditions is correct. If isAllSuccess is false, Tablestore may fail to query data on all servers and return a value that is smaller than the total number of rows that meet the query conditions. 
     */
    if (!resp.isAllSuccess()) {
        System.out.println("NotAllSuccess!");
    }
    System.out.println("IsAllSuccess: " + resp.isAllSuccess());
    System.out.println("TotalCount: " + resp.getTotalCount()); // Display the total number of rows that meet the query conditions. 
    System.out.println(resp.getRequestId());
}

Billing rules

When you use a search index to query data, you are charged for the read throughput that is consumed. For more information, see Billable items of search indexes.

FAQ

How do I query the total number of rows in a table?

References

When you use a search index to query data, you can use the following query methods: term query, terms query, match all query, match query, match phrase query, prefix query, range query, wildcard query, fuzzy query, Boolean query, geo query, nested query, KNN vector query, and exists query. You can select query methods based on your business requirements to query data from multiple dimensions.
You can sort or paginate rows that meet the query conditions by using the sorting and paging features. For more information, see Perform sorting and paging.
You can use the collapse (distinct) feature to collapse the result set based on a specific column. 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, you can use the aggregation feature of the Search operation or execute SQL statements. For example, you can obtain the minimum and maximum values, sum, and total number of rows. For more information, see Aggregation and SQL query.
If you want to 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.