Use Tablestore SDK for .NET to perform a wildcard query - Tablestore

When you perform a wildcard query, you can use the asterisk (*) and question mark (?) wildcard characters in the query to search for data. The asterisk (*) matches a string of any length at, before, or after a search term. The question mark (?) matches a single character in a specific position. The string to match can start with an asterisk (*) or a question mark (?). For example, if you search for the "table*e" string, "tablestore" can be matched.

If you want to use *word* (equivalent to WHERE field_a LIKE '%word%' in SQL) to query data, you can use fuzzy query for better performance. For more information, see Fuzzy query. If you perform a fuzzy query, the query performance is not compromised when the data volume increases.

Note

If you want to use the NOT LIKE operator, you must use WildcardQuery together with mustNotQueries of BoolQuery.

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 search indexes.

Parameters

Parameter	Description
Query	The type of the query. Set this parameter to WildcardQuery.
FieldName	The name of the column that you want to query.
Value	The string that contains wildcard characters. The string cannot exceed 32 characters in length.
TableName	The name of the data table.
IndexName	The name of the search index.
GetTotalCount	Specifies whether to return the total number of rows that meet the query conditions. Default value: false. If you set this parameter to true, the query performance is compromised.
ColumnsToGet	Specifies whether to return all columns in the rows that meet the query conditions. You can specify the ReturnAll, Columns, and ReturnAllFromIndex parameters. The default value of ReturnAll is false, which indicates that not all columns are returned. You can use one of the following methods to specify the columns that you want to return. If you do not use the following methods to specify the columns that you want to return, only the primary key columns are returned. Configure Columns to specify the columns that you want to return. Set ReturnAllFromIndex to true to return all columns from the search index. If you set ReturnAll to true, all columns are returned.

Example

The following sample code shows how to query the rows in which the value of the Keyword_type_col column matches "Search*" in a table.

/// <summary>
/// Query the rows in which the value of the Keyword_type_col column matches "Search*" in a table. 
/// </summary>
/// <param name="otsClient"></param>
public static void WildcardQuery(OTSClient otsClient)
{
    var searchQuery = new SearchQuery();
    // Set the query type to WildcardQuery and specify a string that contains one or more wildcard characters to perform a wildcard query. 
    searchQuery.Query = new WildcardQuery(Keyword_type_col, "*Search*");
    // Return the total number of rows that meet the query conditions. 
    searchQuery.GetTotalCount = true;
    var request = new SearchRequest(TableName, IndexName, searchQuery);
    // You can specify the ColumnsToGet parameter to return the columns that you specify, all columns in the rows that meet the query conditions, or all columns in the search index. If you do not specify this parameter, only the primary key columns are returned. 
    request.ColumnsToGet = new ColumnsToGet()
    {
        // Return all columns in the search index. 
        ReturnAllFromIndex = true
        // Return the columns that you specify. 
        //Columns = new List<string>() { Long_type_col, Text_type_col, Keyword_type_col }
        // Return all columns in the rows that meet the query conditions. 
        //ReturnAll = true
    };

    var response = otsClient.Search(request);

    Console.WriteLine("Total Count:" + response.TotalCount); // Display the total number of rows that meet the query conditions instead of the number of returned rows. 
}

FAQ

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, Boolean query, geo query, nested query, and exists query. You can use different query methods to query data from multiple dimensions based on your business requirements.
You can sort or paginate rows that meet the query conditions by using the sorting and paging features. For more information, see 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.