Tablestore:Sorting and paging

Use scenarios

Index presorting

By default, data in a search index is sorted based on the presorting settings that are specified by the IndexSort parameter. When you use a search index to query data, the presorting settings that are specified by the IndexSort parameter determine the default order in which the matched data is returned.

When you create a search index, you can specify presorting settings by configuring the IndexSort parameter. If you do not specify presorting settings, data in the search index is sorted by primary key value.

Specify a sorting method when you query data

Sorting can be enabled only for fields for which enable_sort_and_agg is set to True.

You can specify a sorting method for each query. Search index-based queries support the following sorting methods. You can also specify multiple sorting methods based on different priorities.

ScoreSort

sort = Sort(
    sorters=[ScoreSort(sort_order=SortOrder.DESC)]
)
client.search(
    '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', SearchQuery(query, sort=sort, limit=100, get_total_count=True), ColumnsToGet(return_type=ColumnReturnType.ALL)
)

PrimaryKeySort

You can use PrimaryKeySort to sort query results based on the value of the primary key.

sort = Sort(
    sorters=[PrimaryKeySort(sort_order=SortOrder.DESC)]
)
client.search(
    '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', SearchQuery(query, sort=sort, limit=100, get_total_count=True), ColumnsToGet(return_type=ColumnReturnType.ALL)
) = PrimaryKeySort(sort_order=SortOrder.DESC)

FieldSort

You can use FieldSort to sort the query results based on the values of one or more specific columns.

• Sort the query results based on the values of a single column

  You can use FieldSort to sort the query results based on the values of a specified column.

  sort = Sort(
      sorters=[FieldSort('a', SortOrder.ASC)]
  )
  
  client.search(
      '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', SearchQuery(query, sort=sort, limit=100, get_total_count=True), ColumnsToGet(return_type=ColumnReturnType.ALL)
  )

• Sort the query results based on the values of multiple columns

  You can also sort query results based on the values of two columns in specific orders to determine the order in which the matched data is returned.

  sort = Sort(
      sorters=[
          FieldSort('a', SortOrder.ASC),
          FieldSort('b', SortOrder.ASC)
      ]
  )
  
  client.search(
      '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', SearchQuery(query, sort=sort, limit=100, get_total_count=True), ColumnsToGet(return_type=ColumnReturnType.ALL)
  )

GeoDistanceSort

You can use GeoDistanceSort to sort query results by geographical location.

sort = Sort(
    sorters=[GeoDistanceSort('g', ['32.5,116.5', '32.0,116.0'], sort_order=SortOrder.DESC, sort_mode=SortMode.MAX)]
)

client.search(
    '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', SearchQuery(query, sort=sort, limit=100, get_total_count=True), ColumnsToGet(return_type=ColumnReturnType.ALL)
)    

Specify a paging method

You can use limit and offset or use tokens to split returned query results into pages.

Configure the limit and offset parameters

If you do not specify values for the limit and offset parameters, the default values are used. The default value of the limit parameter is 10. The default value of the offset parameter is 0.

query = RangeQuery('k', 'key100', 'key500', include_lower=False, include_upper=False)
search_response = client.search(
    '<TABLE_NAME>', '<SEARCH_INDEX_NAME>', 
    SearchQuery(query, offset=100, limit=100, get_total_count=True), 
    ColumnsToGet(return_type=ColumnReturnType.ALL)
)  
print('request_id : %s' % search_response.request_id)
print('is_all_succeed : %s' % search_response.is_all_succeed)
print('total_count : %s' % search_response.total_count)
print('rows : %s' % search_response.rows)

Use a token

We recommend that you use a token for deep paging because this method has no limits on the paging depth.

If Tablestore cannot read full data that meets the query conditions, Tablestore returns next_token. You can use next_token to continue reading the subsequent data.

By default, you can only page backward when you use a token. If you want to page forward, you can cache and use a previous token because tokens are valid during the query.

When you use a token, the sorting method is the same as the method that is used in the previous request. Tablestore sorts data based on the IndexSort field by default or based on the method that you specified. You cannot specify the sorting method when you use a token. You cannot configure the offset parameter when you use a token. Data is returned page by page, which results in a slow query.

query = MatchAllQuery()
all_rows = []
next_token = None
# first round
search_response = client.search('<TABLE_NAME>', '<SEARCH_INDEX_NAME>',
        SearchQuery(query, next_token=next_token, limit=100, get_total_count=True),
        columns_to_get=ColumnsToGet(['k', 't', 'g', 'ka', 'la'], ColumnReturnType.SPECIFIED))
all_rows.extend(search_response.rows)
# loop
while search_response.next_token:
    search_response = client.search('<TABLE_NAME>', '<SEARCH_INDEX_NAME>',
        SearchQuery(query, next_token=search_response.next_token, sort=None, limit=100, get_total_count=True),
        columns_to_get=ColumnsToGet(['k', 't', 'g', 'ka', 'la'], ColumnReturnType.SPECIFIED))
    all_rows.extend(search_response.rows)

print('Total rows:%d' % len(all_rows))

FAQ

• What do I do if no data can be found by calling the Search operation?

• 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, 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 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.