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 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.
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 a data table and Write data.
A search index is created for the data table. For more information, see Create a search index.
Parameters
Parameter | Description |
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. |
query | The type of the query. Set the query parameter to WildcardQuery. |
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. |
weight | The weight that you want to assign to the field that you want to query to calculate the BM25-based keyword relevance score. This parameter is used in full-text search scenarios. If you specify a higher weight for the field that you want to query, the BM25-based keyword relevance score is higher for the field. The value of this parameter is a positive floating point number. This parameter does not affect the number of rows that are returned. However, this parameter affects the BM25-based keyword relevance scores of the query results. |
tableName | The name of the data table. |
indexName | The name of the search index. |
columnsToGet | Specifies whether to return all columns of each row that meets the query conditions. You can specify the returnAll and columns fields for this 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. |
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
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, Boolean query, KNN vector query, nested query, and exists query. 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 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.