You can use match query (MatchQuery) to query data in a table based on approximate matches. Tablestore tokenizes the values in TEXT columns and the keywords you use to perform match queries based on the analyzer that you specify. Therefore, Tablestore can perform match queries based on the tokens. We recommend that you use match phase query (MatchPhraseQuery) for columns for which fuzzy tokenization is used to ensure high performance in fuzzy queries.

Prerequisites

  • An OTSClient instance 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.

Parameters

Parameter Description
FieldName The name of the column that you want to match.

You can perform match queries on TEXT columns.

Text The keyword that is used to match the column values when you perform a match query.

If the column that you want to match is a TEXT column, the keyword is tokenized into multiple tokens based on the analyzer type that you specify when you create the search index. By default, single-word tokenization is performed if you do not specify the analyzer type when you create the search index.

For example, if the column that you want to match is a TEXT column, you set the analyzer type to single-word tokenization, and you use "this is" as a search keyword, you can obtain query results such as "..., this is tablestore", "is this tablestore", "tablestore is cool", "this", and "is".

Query The query type. To use match query, set this parameter to MatchQuery.
Operator The logical operator. By default, OR is used as the logical operator, which indicates that a row meets the query conditions when the column value contains at least the minimum number of tokens.

If you set Operator to AND, a row meets the query conditions only when the column value contains all tokens.

MinimumShouldMatch The minimum number of matched tokens contained in a column value.

A row is returned only when the value of the FieldName column in the row contains at least the minimum number of matched tokens.

Note MinimumShouldMatch must be used together with the OR logical operator.
TableName The name of the table.
IndexName The name of the search index.
GetTotalCount Specifies whether to return the total number of rows that meet the query conditions. The default value of this parameter is false, which indicates 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.

ColumnsToGet Specifies whether to return all columns of each row that meets the query conditions. You can configure ReturnAll, Columns, and ReturnAllFromIndex for this parameter.
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.

Examples

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

    var response = otsClient.Search(request);

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