system Tables in Xpand
MariaDB Xpand includes system tables in the
Rough estimate of progress for an
Per-session statistics on transaction and statement types.
Databases containing Xpand tables.
Stores information on open transactions.
Information on each Replica Server that is currently connected to the Xpand service.
Information related to replication when Xpand is configured for in-bound replication
Details on operations performed by the rebalancer process and the reason why the operation was triggered.
Summary of current rebalancer operations.
Details on Xpand tables in the deployment.
Details on representations produced by each index on each Xpand table. These are the basis for data distribution through the Xpand deployment.
Information on currently connection and recently disconnected sessions.
Internal statistics on database and deployment performance.
Information on database users, host, and password combinations.
Total size of each Xpand table.
Information on table slices, produced by dividing representations of each Xpand table.
History of installation and upgrade versions.
The ID for the session.
The name of the source relation.
Timestamp for when the alter started.
The number of rows read by the ALTER.
The estimated number of rows in the source relation
A rough estimate of when the ALTER might finish.
The databases table contains one row for each database in the system. Its columns are as follows:
Contains an ID for each database. It corresponds to the db column in the relations table.
Contains the ID of the user who created the database. It corresponds to the user column of the users table.
Name of the database.
Indicates whether the table is hidden from users when performing queries. 1 = yes, 0 = no.
An internal value that encodes the character set and collation sequence utilized by a given database.
To translate this encoded value to English, a special function is available as follows:
This table contains a row for each open transaction.
This table contains a detailed log of Rebalancer actions and the reasons for those actions. For additional information, see "Manage the Rebalancer for MariaDB Xpand".
The cluster performs ongoing optimization tasks in background mode. In rare cases, this background activity might affect query performance. In such cases, the Rebalancer, which moves data between disks and nodes to ensure even distribution, is a likely source. Rebalancing typically runs after an import, and occasionally runs as disk utilization increases. Because Rebalancer sessions can be brief, the rebalancer_
Values returned in the action column are as follows:
A slice has grown too large and is being split into two smaller slices.
A slice is being moved to another disk or node to optimize the load.
A slice is being duplicated, usually during the reprotection stage after a hardware failure.
The relations table contains one row for each table in the system.
The representations table contains one row per representation in the system. Each relation and each index on that relation constitutes a representation. The base column indicates when the representation is the Base Representation.
The sessions table contains information about all currently connected and recently disconnected client sessions.
The stats table contains internally-collected statistics about database and cluster performance. Most of these statistics are for internal use, but some are of general interest.
Stores histograms of node to node network latencies.
Representations are split into slices and distributed throughout your cluster. The table_
Each slice contains a unique set of rows from the table. The complete table is represented by assembling all the rows from the table slices. The rows are allocated to slices using a hash that is based on the row's index or indices. The number of slices per table depends on many factors including the size of the cluster. To configure this setting, issue the ALTER TABLE SET SLICES = <N> command. Changing the slice count can improve performance. For details, contact MariaDB support.
To display the names of the database, table, and indexes for each slice, join on the slice column.
Database user, host, and password combinations are stored in the users table. Join to this table to display user names instead of user ids. For additional information, see "Database User Accounts for MariaDB Xpand".