Database limits

This section describes the parameters of limits set in YDB.

Schema object limits

The table below shows the limits that apply to schema objects: tables, databases, and columns. The Object column specifies the type of schema object that the limit applies to.
The Error type column shows the status that the query ends with if an error occurs. For more information about statuses, see Error handling in the API.

Object Limit Value Explanation Internal
name
Error
type
Database Maximum path depth 32 Maximum number of nested path elements (directories, tables). MaxDepth SCHEME_ERROR
Database Maximum number of paths (schema objects) 200,000 Maximum number of path elements (directories, tables) in a database. MaxPaths GENERIC_ERROR
Database Maximum number of tablets 200,000 Maximum number of tablets (table shards and system tablets) that can run in the database. An error is returned if a query to create, copy, or update a table exceeds this limit. When a database reaches the maximum number of tablets, no automatic table sharding takes place. MaxShards GENERIC_ERROR
Database Maximum object name length 255 Limits the number of characters in the name of a schema object, such as a directory or a table MaxPathElementLength SCHEME_ERROR
Database Maximum ACL size 10 KB Maximum total size of all access control rules that can be saved for the schema object in question. MaxAclBytesSize GENERIC_ERROR
Directory Maximum number of objects 100,000 Maximum number of tables and child directories created in a directory. MaxChildrenInDir SCHEME_ERROR
Table Maximum number of table shards 35,000 Maximum number of table shards. MaxShardsInPath GENERIC_ERROR
Table Maximum number of columns 200 Limits the total number of columns in a table. MaxTableColumns GENERIC_ERROR
Table Maximum column name length 255 Limits the number of characters in a column name MaxTableColumnNameLength GENERIC_ERROR
Table Maximum number of columns in a primary key 20 Each table must have a primary key. The number of columns in the primary key may not exceed this limit. MaxTableKeyColumns GENERIC_ERROR
Table Maximum number of indexes 20 Maximum number of indexes other than the primary key index that can be created in a table. MaxTableIndices GENERIC_ERROR
Table Maximum number of followers 3 Maximum number of read-only replicas that can be specified when creating a table with followers. MaxFollowersCount GENERIC_ERROR
Table Maximum number of tables to copy 1000 Limit on the size of the table list for persistent table copy operations MaxConsistentCopyTargets GENERIC_ERROR

Size limits for stored data

Parameter Value Error type
Maximum total size of all columns in a primary key 1 MB GENERIC_ERROR
Maximum size of a string column value 8 MB GENERIC_ERROR

Limits that apply when executing queries

The table below lists the limits that apply to query execution. The Call column specifies the public API call that will end with the error status specified in the Status column.

Parameter Value Call Explanation Status
in case of
a violation
of the limit
Maximum number of rows in query results 1000 ExecuteDataQuery Complete results of some queries executed using the ExecuteDataQuery method may contain more rows than allowed. In this case, a query will return the maximum number of rows allowed, and the result will have the truncated flag set. SUCCESS
Maximum query result size 50 MB ExecuteDataQuery Complete results of some queries may exceed the set limit. In this case, a query will fail returning no data. PRECONDITION_FAILED
Maximum number of sessions per cluster node 1000 CreateSession Using the library for working with YDB, an application can create sessions within a connection. Sessions are linked to a node. You can create a limited number of sessions with a single node. OVERLOADED
Maximum query text length 10 KB ExecuteDataQuery Limit on the length of YQL query text. BAD_REQUEST
Maximum size of parameter values 50 MB ExecuteDataQuery Limit on the total size of the parameters passed when executing a previously prepared query. BAD_REQUEST