Database Limits
This section lists the limits that are applied to database objects in Yellowbrick databases.
Database Limit | Value | Notes |
---|---|---|
Databases per appliance | 1,000 | The maximum number of databases includes the yellowbrick
database, so the effective limit is 999 user-created databases. |
Tables per appliance | 70,000 | There is no limit on the number of tables per database, only a limit on the total number per appliance. This limit applies to persistent tables only. |
Size of internal temporary tables | 30MB | Temporary tables that the system creates during queries are limited to a size of 30MB. This limitation does not apply to temporary tables created by users. |
Columns per table or view | 2000 | Increased in Version 5.2.9. In addition to being a storage limit, this
limit defines the maximum number of columns that can be placed in a row.
Therefore, the output of a In practice, the limit applies to the number of columns
that have to be propagated up the query plan tree during execution. Therefore,
you may find that less than 2000 columns can be selected because of the behavior
of the plan. Columns that are not in the select list but are needed for
its computation (such as For example, a simple
query that selects one column but orders by another column propagates two
columns, not
one:
|
Rows per table | 264 | |
Maximum width of a row in a column | 64231 bytes | A single row can be 231 bytes longer than any single VARCHAR
column. See Maximum Row Size. |
Length of a VARCHAR column |
64000 bytes | For other data type limits, see SQL Data Types. |
Length of database object names | 128 bytes | See SQL Identifiers. |
Number of distribution columns per table | 1 | See Distribution Options. |
Number of sort columns per table | 1 | See Sorted and Clustered Tables. |
Number of cluster columns per table | 4 | See Sorted and Clustered Tables. |
Number of partition columns per table | 4 | See Partitioning Options. |
Maximum number of IN list items |
200000 | See IN. |
Maximum number of WHEN clauses in a CASE
expression |
8192 | |
Maximum number of ACLs per database object | 5000 | The maximum number of privileges you can grant to a database object is 5000. |
User connection/session limits
(max_user_connections ) |
2000 | The maximum number of database user connections is 2000. (The related
max_connections value is 2300, which allows for 300 additional
system user connections; max_user_connections must be set to a
lower value than max_connections .) See also Managing Idle Sessions. |
Replicas per database | 1 | See Database Replication. |
Maximum Row Size
When you create a table, the maximum row limit of 64231 bytes is not enforced. However, you will not be able to insert more than 64231 bytes into a table (as an absolute maximum), and depending on the definition of the columns in the table, the actual limit on the stored size of a row may be smaller.
- If a column (of any type) can be
NULL
: + 1 byteFor example, a
CHAR(10)
column that acceptsNULL
values occupies 11 bytes. - If the declared length of a
VARCHAR
column <= 30: declared length + 2For example, a
VARCHAR(25)
column always occupies 27 bytes (or 28 if it is nullable). VARCHAR
columns >30: byte length + 2 + 8For example, a
VARCHAR(500)
column occupies its actual length + 10 bytes. If 500 bytes are inserted, its size is 510 bytes (or 511 if it is nullable). If 100 bytes are inserted, its size is 110 bytes (or 111 if it is nullable).
Practical Limits for Numbers of Tables and Partitions
Yellowbrick does not enforce limits on either the number of tables per database or the number of partitions per table. The maximum number of tables is 70,000 per appliance, regardless of the number of databases you create. Ideally, the number of partitions created per table should be less than 1,000. (See Partitioning Tables for details about how the actual number of partitions is computed, based on the partitioning columns you define. The enforced maximum is approximately 250,000 partitions.)