Exists query - Tablestore SDK for Python - Tablestore - Alibaba Cloud Documentation Center

Prerequisites

Install the Tablestore SDK for Python and initialize a client.

Description

An exists query, also called a NULL query, matches rows in which a specified indexed field exists. A field does not exist if the corresponding column was not written to the table. An empty array is also treated as a nonexistent field. To query a Nested field or one of its child fields, wrap ExistsQuery in NestedQuery. To match rows in which the field does not exist, add ExistsQuery to BoolQuery.must_not_queries. When you call the search method, set the query type to ExistsQuery.

ExistsQuery(field_name)

The following example queries rows in which the city field exists and returns up to 10 rows and the total number of matching rows.

query = ExistsQuery("city")
search_query = SearchQuery(
    query,
    limit=10,
    get_total_count=True,
)
response = client.search(
    "example_table",
    "example_index",
    search_query,
    ColumnsToGet(return_type=ColumnReturnType.ALL),
)
print(response.total_count)
for row in response.rows:
    print(row)

Parameters

Search request

The search method contains the following parameters.

Name	Type	Description
table_name (required)	`str`	The name of the data table.
index_name (required)	`str`	The name of the search index.
search_query (required)	`SearchQuery`	The query condition and common query configurations.
columns_to_get (optional)	`ColumnsToGet`	The return column configuration. If this parameter is not specified, only primary key columns are returned.
routing_keys (optional)	`list`	The list of primary key values for custom routing fields. You do not need to specify this parameter if custom routing is not configured.
timeout_s (optional)	`int`	The request timeout in seconds. If this parameter is not specified, the client-level timeout is used.

Query configuration

search_query is of the SearchQuery type and contains the following parameters.

Name	Type	Description
query (required)	`Query`	The query condition. Set this parameter to `ExistsQuery`.
sort (optional)	`Sort`	The sort order of query results. For more information, see Sort and paginate results.
get_total_count (optional)	`bool`	Specifies whether to return the total number of matching rows. Default value: `False`. Setting this parameter to `True` increases query overhead.
next_token (optional)	`bytes`	The pagination token. Set this parameter to `next_token` from the previous response to retrieve the next page. For more information, see Sort and paginate results.
offset (optional)	`int`	The offset from which the current query starts. Use this parameter for shallow pagination.
limit (optional)	`int`	The maximum number of rows to return. If this parameter is set to `0`, no row data is returned.
aggs (optional)	`list[Agg]`	The aggregation configurations. For more information, see Aggregation.
group_bys (optional)	`list[BaseGroupBy]`	The grouping configurations. For more information, see Aggregation.
collapse_field (optional)	`Collapse`	The result collapsing configuration, which removes duplicate results based on a specified field. For more information, see Collapse query results.

Query condition

search_query.query is of the ExistsQuery type and contains the following parameters.

Name	Type	Description
field_name (required)	`str`	The name of the indexed field to query.

Return columns

columns_to_get is of the ColumnsToGet type and contains the following parameters.

Name	Type	Description
column_names (optional)	`list[str]`	The names of attribute columns to return. Specify this parameter only when `return_type` is `SPECIFIED`.
return_type (optional)	`ColumnReturnType`	The return column mode. `NONE` (default) returns only primary key columns; `SPECIFIED` returns the attribute columns in `column_names`; `ALL` returns all attribute columns from the table; and `ALL_FROM_INDEX` returns all indexed attribute columns.

Response

The search method returns SearchResponse. The following table describes the core fields.

Field	Type	Description
rows	`list[Row]`	The rows returned by the current query. The number of rows does not exceed `limit`.
next_token	`bytes`	The token for the next page. If this field is not empty, pass it to the next request to continue reading.
total_count	`int`	The number of matching rows. The value depends on the `get_total_count` configuration.
is_all_succeed	`bool`	Indicates whether all index partitions were queried. If the value is `False`, partial results are returned and `total_count` may be less than the actual number of matching rows.
agg_results	`list[AggResult]`	The aggregation results. This field is empty if `aggs` is not configured.
group_by_results	`list[GroupByResult]`	The grouping results. This field is empty if `group_bys` is not configured.
search_hits	`list[SearchHit]`	The search hits, including extended information such as relevance scores, highlights, and matching child rows.

Tuple-compatible response

Starting from Tablestore SDK for Python 5.2.0, search APIs return response objects instead of tuples. Version 5.1.0 and earlier return tuples directly. In version 5.2.1 and later, you can call SearchResponse.v1_response() to obtain a tuple compatible with earlier versions. For new code, access SearchResponse attributes directly to avoid unpacking errors if response fields are extended.

(
    rows,
    next_token,
    total_count,
    is_all_succeed,
    agg_results,
    group_by_results,
    search_hits,
) = response.v1_response()