Tablestore:Wildcard query

Background information

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 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 tokenization-based wildcard query. For more information, see Tokenization-based wildcard query. The query performance is not compromised when the data volume increases.

Prerequisites

• A Tablestore client is initialized. For more information, see Initialize a Tablestore client.

• A data table is created. Data is written to the table. For more information, see Create a data table and Write data.

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

Parameters

Examples

The following sample code provides an example on how to query rows in which the value of the Col_Keyword column matches the "hang*u" pattern.

/**
 * Search the table for rows in which the value of the Col_Keyword column matches the "hang*u" pattern. 
 * @param client
 */
private static void wildcardQuery(SyncClient client) {
    SearchQuery searchQuery = new SearchQuery();
    WildcardQuery wildcardQuery = new WildcardQuery(); // Use WildcardQuery. 
    wildcardQuery.setFieldName("Col_Keyword");
    wildcardQuery.setValue("hang*u"); // Specify a string that contains one or more wildcard characters in wildcardQuery. 
    searchQuery.setQuery(wildcardQuery);
    //searchQuery.setGetTotalCount(true); // Specify that the total number of matched rows is returned. 

    SearchRequest searchRequest = new SearchRequest("<TABLE_NAME>", "<SEARCH_INDEX_NAME>", 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); // Specify that all columns are returned. 
    //columnsToGet.setColumns(Arrays.asList("ColName1","ColName2")); // Specify the columns that you want to return. 
    //searchRequest.setColumnsToGet(columnsToGet);

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

FAQ

• What do I do If the "length of field value is longer than 32 for the [WILDCARD_QUERY] query" exception occurs when I query data by using wildcard query?

• What do I do if no data is found when I call the Search operation for search indexes?

• 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

• 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, geo query, KNN vector query, Boolean query, nested query, and exists query. After you create a search index, you can use the query methods provided by the search index 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 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 table, you can call the Search operation to use the aggregation feature or use the SQL query feature. For example, you can query the maximum and minimum values, the sum of the values, and the 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.