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

  • The OTSClient 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 query.

Match query applies to TEXT columns.

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

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

For example, if you set the tokenization method to single-word tokenization and 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, which is set to matchQuery.
offset The position from which the current query starts.
limit The maximum number of rows that you want the current query to return.

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

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.
operator The logical operator. By default, OR is used as the logical operator, which specifies that a row matches the query conditions when one of the tokens is matched.

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

getTotalCount Specifies whether to return the total number of rows that match the query conditions. By default, the value of this parameter is false, which specifies that the total number of rows that match the query conditions is not returned.

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

tableName The name of the data table.
indexName The name of the search index.
columnsToGet Specifies whether to return all columns of each matched row. You can configure returnAll and columns for this parameter.

By default, the value of returnAll is false, which specifies that not all columns are returned. In this case, you can use columns 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 returnAll is set to true, all columns are returned.

Examples

/**
 * Search the table for rows in which the value in Col_Keyword matches "hangzhou". Tablestore returns part of the matched rows and the total number of matched rows in this query. 
 * @param client
 */
private static void matchQuery(SyncClient client) {
    SearchQuery searchQuery = new SearchQuery();
    MatchQuery matchQuery = new MatchQuery(); // Set the query type to MatchQuery. 
    matchQuery.setFieldName("Col_Keyword"); // Specify the name of the column that you want to query. 
    matchQuery.setText("hangzhou"); // Specify the keyword that you want to match. 
    searchQuery.setQuery(matchQuery);
    searchQuery.setOffset(0); // Set offset to 0. 
    searchQuery.setLimit(20); // Set limit to 20 to return up to 20 rows. 
    //searchQuery.setGetTotalCount(true); // Specify that the total number of matched rows is returned. 

    SearchRequest searchRequest = new SearchRequest("sampleTable", "sampleSearchIndex", searchQuery);
    // You can configure the columnsToGet parameter to specify the columns to return or specify that all columns are returned. If you do not configure this parameter, only the primary key columns are returned. 
    //SearchRequest.ColumnsToGet columnsToGet = new SearchRequest.ColumnsToGet();
    //columnsToGet.setReturnAll(true); // Set ReturnAll to true to return all columns. 
    //columnsToGet.setColumns(Arrays.asList("ColName1","ColName2")); // Set Columns to return the columns that you want to return. 
    //searchRequest.setColumnsToGet(columnsToGet);

    SearchResponse resp = client.search(searchRequest);
    //System.out.println("TotalCount: " + resp.getTotalCount()); // Specify that the total number of matched rows instead of the number of returned rows is displayed. 
    System.out.println("Row: " + resp.getRows());
}