Search index limits - Tablestore - Alibaba Cloud Documentation Center

This topic describes the limits on search indexes. The limits include the limits on field mappings, limits on data queries performed by calling the Search and ParallelScan operations, and limits on search index metrics such as the rate, total size, and row count. This topic also describes regions in which the search index feature is available.

Mapping

The following table describes the limits on field mappings to consider when you create a search index. The limits include the limits on the field length, number of index fields, field types, nested types, and table fields.

Item	Maximum value	Description
Number of index fields	1000	The number of fields that can be indexed.
Array length	256	The maximum number of elements in an array.
Number of nested levels	5	Up to five levels can be nested.
Number of subfields in a Nested field	256	The maximum number of subfields in a Nested field.
Number of Nested fields	100	The number of subfields that can be nested.
Total length of values in all primary key columns	1,000 bytes	The total length of values in all primary key columns in each row can be up to 1,000 bytes.
Length of the value in a primary key column of the String type	1,000 bytes	To index a primary key column of the String type, the value of the column cannot exceed 1,000 bytes in length.
Length of the value in an attribute column of the String type when you want to index the column as Keyword	4 KB	None.
Length of the value in an attribute column of the String type when you want to index the column as Text	2 MB	In most cases, the limit is the same as the length limit on an attribute column in a data table. When you perform fuzzy query based on fuzzy tokenization for a Text field and the value of the Text field exceeds 1,024 characters in length, Tablestore truncates and discards the excess characters, and tokenizes only the first 1,024 characters.
Length of a query string for a wildcard query	32	The query string can be up to 32 characters in length.
Length of a query string for a prefix query	1,000 bytes	The query string can be up to 1,000 bytes in length.
Maximum number of fields of the Vector type in a search index	1	A search index can contain only one field of the Vector type. To increase the limit, submit a ticket.
Maximum number of dimensions for a field of the Vector type in a search index	2048	The limit is the same as the maximum number of dimensions of vectors.
Top K query results that have the highest similarity to the vector that you want to query in a KNN vector query	1000	Up to 1,000 query results that have the highest similarity can be returned for a KNN vector query.

Search

The following table describes the limits when you call the Search operation to query and analyze data.

Category	Item	Maximum value	Description
General limits	offset+limit	50000	To increase the number of returned rows, configure the next_token parameter.
	limit	100	Default value: 10. Maximum value: 100. If you call the Search operation to query data of the specified column, the value of the limit parameter can be up to 1000 when the data is contained in search indexes. Therefore, up to 1,000 rows can be returned per request. To increase the limit, submit a ticket.
	timeout	10s	None.
	CU	None.	None.
	QPS	100,000	The upper limit for lightweight transaction processing is 100,000 queries per second (QPS). To increase the limit, submit a ticket.
	Number of specified query methods in a Search operation	1024	Query performance is compromised when complex nested queries are specified in a Search operation. We recommend that you simplify the queries.
	Maximum number of keywords in a terms query	1024	Up to 1,024 keywords are supported in a terms query.
Full-text search	Number of highlighted text fragments	500	The total number of highlighted text fragments that can be returned when the conditions specified by the inner_hits and highlight parameters are met.
Full-text search	Number of fields for which you can enable the highlight feature	10	You can enable the highlight feature for up to 10 fields in a query.
Aggregation	Number of Aggregations at the same level	5	The number of Aggregations is recalculated each time you add a new Aggregation to SubGroupBy.
	Number of GroupBys at the same level	5	The number of GroupBys is recalculated each time you add a new GroupBy to SubGroupBy.
	Number of nested GroupBys	3	The root GroupBy is counted as a nested level.
	Number of Filters in GroupByFilter	10	None.
	Number of groups returned by GroupByField	2,000	None.
	Number of internal sources of GroupByComposite	32	The maximum number of columns supported by a multi-column field group.
	Number of Ranges in GroupByRange	100	None.
	Number of Ranges in GroupByGeodistance	10	None.

ParallelScan

The following table describes the limits when you call the ParallelScan operation to query data and export data in parallel.

Category	Item	Description
General limits	offset+limit	When you use parallel scan, you cannot configure the offset and limit parameters. The results that are returned are displayed in chronological order.
	limit	The maximum value is 2,000.
	CU	None.
	QPS	None.
	Maximum number of parallel scan tasks in a ParallelScan call	The value of the MaxParallel parameter. You can call the ComputeSplits operation to obtain the value of the parameter.
	Maximum validity period of a parallel scan task	The maximum validity period (aliveTime) of a parallel scan task is 10 minutes.
	Maximum number of parallel scan tasks	The maximum number of parallel scan tasks is 10. Parallel scan tasks that have the same session ID and the same ScanQuery value are considered one task. For more information, see Parallel scan.

Index

The following table describes the limits on search index metrics, such as the rate, synchronization latency, number of rows, and total size.

Item	Maximum value	Description
Rate	50,000 rows/s	The first time data is written to a table or when a large volume of data is written in a short period of time, Tablestore balances loads within a few minutes. The maximum rate of indexing for Text fields is limited to 10,000 rows/s because the process consumes a large number of CPU resources for tokenization. To increase the limit, submit a ticket.
Synchronization latency	3s	In most cases, the synchronization latency is within 3 seconds. Up to 1 minute is required to initialize a new index.
Number of rows in an index	100 billion	To increase the limit, submit a ticket.
Total size	100 TB	To increase the limit, submit a ticket.

Other limits

Currently, the search index feature is supported in the following regions: China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Zhangjiakou), China (Ulanqab), China (Shenzhen), China (Guangzhou), China (Chengdu), China (Hong Kong), Singapore, Malaysia (Kuala Lumpur), Indonesia (Jakarta), Japan (Tokyo), Germany (Frankfurt), UK (London), US (Silicon Valley), US (Virginia), Thailand (Bangkok), SAU (Riyadh- Partner Region), and Philippines (Manila). Take note that the KNN vector query feature is not supported in the US (Silicon Valley) region.

Note

If your business requirements are not met due to the preceding limits, go to the Alibaba Cloud official website and submit a ticket. When you submit a ticket, you must specify the limits you want to adjust and your desired limit values. You must also specify the scenarios in which you want to use the new limits and why you require these new limits. The requirements that you specify in the ticket are recorded to help inform future development.