MatrixOne System Database and Tables

MatrixOne system database and tables are where MatrixOne stores system information. We can access the system information through them. MatrixOne creates 6 system databases at initialization: mo_catalog, information_schema, system_metrcis, system, mysql, and mo_task. mo_task is under development and have no direct impact on users. The other system databases and table functions are described in this document.

The system can only modify system databases and tables, and users can only read from them.

mo_catalog database

mo_catalog stores the metadata of MatrixOne objects: databases, tables, columns, system variables, accounts, users, and roles.

Start with MatrixOne 0.6 has introduced the concept of multi-account, the default sys account and other accounts have slightly different behaviors. The system table mo_account, which serves the multi-tenancy management, is only visible for the sys account; the other accounts don’t see this table.

mo_database table

mo_tables table

mo_columns table

mo_table_partitions table

mo_account table (Only visible for sys account)

mo_role table

mo_user table

mo_user_grant table

mo_role_grant table

mo_role_privs table

mo_stages table

mo_user_defined_function table

mo_mysql_compatbility_mode table

mo_pubs table

mo_indexes table

system_metrics database

system_metrics collect the status and statistics of SQL statements, CPU & memory resource usage.

system_metrics tables have more or less same column types, fields in these tables are described as follows:

• collecttime:Collection time

• value: the value of the collecting metric

• node: the MatrixOne node uuid

• role: the MatrixOne node role, can be CN, TN or LOG.

• account: default as “sys”, the account who fires the SQL request.
• type:SQL type, can be select, insert, update, delete, other types.

metric table

The other tables are all views of the metric table:

• process_cpu_percent table: Process CPU busy percentage.
• process_open_fs table: Number of open file descriptors.
• process_resident_memory_bytes table: Resident memory size in bytes.
• server_connection table: Server connection numbers.
• sql_statement_errors table: Counter of sql statements executed with errors.
• sql_statement_total table: Counter of executed sql statement.
• sql_transaction_errors table: Counter of transactional statements executed with errors.
• sql_statement_hotspot table: records the most extended SQL query executed by each tenant within each minute. Only those SQL queries whose execution time does not exceed a certain aggregation threshold will be included in the statistics.
• sql_transaction_total table: Counter of transactional sql statement.
• sys_cpu_combined_percent table: System CPU busy percentage, average among all logical cores.
• sys_cpu_seconds_total table: System CPU time spent in seconds, normalized by number of cores
• sys_disk_read_bytes table: System disk read in bytes.
• sys_disk_write_bytes table: System disk write in bytes.
• sys_memory_available table: System memory available in bytes.
• sys_memory_used table: System memory used in bytes.
• sys_net_recv_bytes table: System net received in bytes.
• sys_net_sent_bytes table: System net sent in bytes.

system database

System database stores MatrixOne historical SQL statements, system logs, error information.

statement_info table

It records user and system SQL statement with detailed information.

rawlog table

It records very detailed system logs.

The other 3 tables(log_info, span_info and error_info) are views of statement_info and rawlog table.

information_schema database

Information Schema provides an ANSI-standard way of viewing system metadata. MatrixOne also provides a number of custom information_schema tables, in addition to the tables included for MySQL compatibility.

Many INFORMATION_SCHEMA tables have a corresponding SHOW command. The benefit of querying INFORMATION_SCHEMA is that it is possible to join between tables.

Tables for MySQL compatibility

CHARACTER_SETS table

The description of columns in the CHARACTER_SETS table is as follows:

• CHARACTER_SET_NAME: The name of the character set.
• DEFAULT_COLLATE_NAME The default collation name of the character set.
• DESCRIPTION The description of the character set.
• MAXLEN The maximum length required to store a character in this character set.

COLUMNS table

The description of columns in the COLUMNS table is as follows:

• TABLE_CATALOG: The name of the catalog to which the table with the column belongs. The value is always def.
• TABLE_SCHEMA: The name of the schema in which the table with the column is located.
• TABLE_NAME: The name of the table with the column.
• COLUMN_NAME: The name of the column.
• ORDINAL_POSITION: The position of the column in the table.
• COLUMN_DEFAULT: The default value of the column. If the explicit default value is NULL, or if the column definition does not include the default clause, this value is NULL.
• IS_NULLABLE: Whether the column is nullable. If the column can store null values, this value is YES; otherwise, it is NO.
• DATA_TYPE: The type of data in the column.
• CHARACTER_MAXIMUM_LENGTH: For string columns, the maximum length in characters.
• CHARACTER_OCTET_LENGTH: For string columns, the maximum length in bytes.
• NUMERIC_PRECISION: The numeric precision of a number-type column.
• NUMERIC_SCALE: The numeric scale of a number-type column.
• DATETIME_PRECISION: For time-type columns, the fractional seconds precision.
• CHARACTER_SET_NAME: The name of the character set of a string column.
• COLLATION_NAME: The name of the collation of a string column.
• COLUMN_TYPE: The column type.
• COLUMN_KEY: Whether this column is indexed. This field might have the following values:
  • Empty: This column is not indexed, or this column is indexed and is the second column in a multi-column non-unique index.
  • PRI: This column is the primary key or one of multiple primary keys.
  • UNI: This column is the first column of the unique index.
  • MUL: The column is the first column of a non-unique index, in which a given value is allowed to occur for multiple times.
• EXTRA: Any additional information of the given column.
• PRIVILEGES: The privilege that the current user has on this column.
• COLUMN_COMMENT: Comments contained in the column definition.
• GENERATION_EXPRESSION: For generated columns, this value displays the expression used to calculate the column value. For non-generated columns, the value is empty.
• SRS_ID: This value applies to spatial columns. It contains the column SRID value that indicates the spatial reference system for values stored in the column.

ENGINES table

The description of columns in the ENGINES table is as follows:

• ENGINES: The name of the storage engine.
• SUPPORT: The level of support that the server has on the storage engine.
• COMMENT: The brief comment on the storage engine.
• TRANSACTIONS: Whether the storage engine supports transactions.
• XA: Whether the storage engine supports XA transactions.
• SAVEPOINTS: Whether the storage engine supports savepoints.

PARTITIONS table

The description of columns in the PARTITIONS table is as follows:

• TABLE_CATALOG: The name of the catalog to which the table belongs. This value is always def.
• TABLE_SCHEMA: The name of the schema (database) to which the table belongs.
• TABLE_NAME: The name of the table containing the partition.
• PARTITION_NAME: The name of the partition.
• SUBPARTITION_NAME: If the PARTITIONS table row represents a subpartition, the name of subpartition; otherwise NULL.
• PARTITION_ORDINAL_POSITION: All partitions are indexed in the same order as they are defined, with 1 being the number assigned to the first partition. The indexing can change as partitions are added, dropped, and reorganized; the number shown is this column reflects the current order, taking into account any indexing changes.
• SUBPARTITION_ORDINAL_POSITION: Subpartitions within a given partition are also indexed and reindexed in the same manner as partitions are indexed within a table.
• PARTITION_METHOD: One of the values RANGE, LIST, HASH, LINEAR HASH, KEY, or LINEAR KEY. Note: MatrixOne does not currently support RANGE and LIST partitioning.
• SUBPARTITION_METHOD: One of the values HASH, LINEAR HASH, KEY, or LINEAR KEY.
• PARTITION_EXPRESSION: The expression for the partitioning function used in the CREATE TABLE or ALTER TABLE statement that created the table’s current partitioning scheme.
• SUBPARTITION_EXPRESSION: This works in the same fashion for the subpartitioning expression that defines the subpartitioning for a table as PARTITION_EXPRESSION does for the partitioning expression used to define a table’s partitioning. If the table has no subpartitions, this column is NULL.
• PARTITION_DESCRIPTION: This column is used for RANGE and LIST partitions. For a RANGE partition, it contains the value set in the partition’s VALUES LESS THAN clause, which can be either an integer or MAXVALUE. For a LIST partition, this column contains the values defined in the partition’s VALUES IN clause, which is a list of comma-separated integer values. For partitions whose PARTITION_METHOD is other than RANGE or LIST, this column is always NULL. Note: MatrixOne does not currently support RANGE and LIST partitioning.
• TABLE_ROWS: The number of table rows in the partition.
• AVG_ROW_LENGTH: The average length of the rows stored in this partition or subpartition, in bytes. This is the same as DATA_LENGTH divided by TABLE_ROWS.
• DATA_LENGTH: The total length of all rows stored in this partition or subpartition, in bytes; that is, the total number of bytes stored in the partition or subpartition.
• INDEX_LENGTH: The length of the index file for this partition or subpartition, in bytes.
• DATA_FREE: The number of bytes allocated to the partition or subpartition but not used.
• CREATE_TIME: The time that the partition or subpartition was created.
• UPDATE_TIME: The time that the partition or subpartition was last modified.
• CHECK_TIME: The last time that the table to which this partition or subpartition belongs was checked.
• CHECKSUM: The checksum value, if any; otherwise NULL.
• PARTITION_COMMENT: The text of the comment, if the partition has one. If not, this value is empty. The maximum length for a partition comment is defined as 1024 characters, and the display width of the PARTITION_COMMENT column is also 1024, characters to match this limit.
• NODEGROUP: This is the nodegroup to which the partition belongs.
• TABLESPACE_NAME: The name of the tablespace to which the partition belongs. The value is always DEFAULT.

PROCESSLIST table

Fields in the PROCESSLIST table are described as follows:

• ID: The ID of the user connection.
• USER: The name of the user who is executing PROCESS.
• HOST: The address that the user is connecting to.
• DB: The name of the currently connected default database.
• COMMAND: The command type that PROCESS is executing.
• TIME: The current execution duration of PROCESS, in seconds.
• STATE: The current connection state.
• INFO: The requested statement that is being processed.

SCHEMATA table

The SCHEMATA table provides information about databases. The table data is equivalent to the result of the SHOW DATABASES statement. Fields in the SCHEMATA table are described as follows:

• CATALOG_NAME: The catalog to which the database belongs.
• SCHEMA_NAME: The database name.
• DEFAULT_CHARACTER_SET_NAME: The default character set of the database.
• DEFAULT_COLLATION_NAME: The default collation of the database.
• SQL_PATH: The value of this item is always NULL.
• DEFAULT_TABLE_ENCRYPTION: defines the default encryption setting for databases and general tablespaces.

TABLES table

The description of columns in the TABLES table is as follows:

• TABLE_CATALOG: The name of the catalog which the table belongs to. The value is always def.
• TABLE_SCHEMA: The name of the schema which the table belongs to.
• TABLE_NAME: The name of the table.
• TABLE_TYPE: The type of the table. The base table type is BASE TABLE, the view table type is VIEW, and the INFORMATION_SCHEMA table type is SYSTEM VIEW.
• ENGINE: The type of the storage engine.
• VERSION: Version. The value is 10 by default.
• ROW_FORMAT: The row format. The value is Compact, Fixed, Dynamic, Compressed, Redundant.
• TABLE_ROWS: The number of rows in the table in statistics. For INFORMATION_SCHEMA tables, TABLE_ROWS is NULL.
• AVG_ROW_LENGTH: The average row length of the table. AVG_ROW_LENGTH = DATA_LENGTH / TABLE_ROWS.
• DATA_LENGTH: Data length. DATA_LENGTH = TABLE_ROWS * the sum of storage lengths of the columns in the tuple.
• MAX_DATA_LENGTH: The maximum data length. The value is currently 0, which means the data length has no upper limit.
• INDEX_LENGTH: The index length. INDEX_LENGTH = TABLE_ROWS * the sum of lengths of the columns in the index tuple.
• DATA_FREE: Data fragment. The value is currently 0.
• AUTO_INCREMENT: The current step of the auto- increment primary key.
• CREATE_TIME: The time at which the table is created.
• UPDATE_TIME: The time at which the table is updated.
• CHECK_TIME: The time at which the table is checked.
• TABLE_COLLATION: The collation of strings in the table.
• CHECKSUM: Checksum.
• CREATE_OPTIONS: Creates options.
• TABLE_COMMENT: The comments and notes of the table.

USER_PRIVILEGES table

The USER_PRIVILEGES table provides information about global privileges.

Fields in the USER_PRIVILEGES table are described as follows:

• GRANTEE: The name of the granted user, which is in the format of 'user_name'@'host_name'.
• TABLE_CATALOG: The name of the catalog to which the table belongs. This value is always def.
• PRIVILEGE_TYPE: The privilege type to be granted. Only one privilege type is shown in each row.
• IS_GRANTABLE: If you have the GRANT OPTION privilege, the value is YES; otherwise, the value is NO.

VIEW table

• TABLE_CATALOG: The name of the catalog the view belongs to. The value is def.
• TABLE_SCHEMA: The name of the database to which the view belongs.
• TABLE_NAME: The name of the view.
• VIEW_DEFINITION: The SELECT statement that provides the view definition. It contains most of what you see in the “Create Table” column generated by SHOW Create VIEW.
• CHECK_OPTION: The value of the CHECK_OPTION property. Values are NONE, CASCADE, or LOCAL.
• IS_UPDATABLE: Set a flag called the view updatable flag when CREATE VIEW; if UPDATE and DELETE (and similar operations) are legal for the view, the flag is set to YES(true). Otherwise, the flag is set to NO(false).
• DEFINER: The account of the user who created the view, in the format username@hostname.
• SECURITY_TYPE: View the SQL SECURITY attribute. Values ​​are DEFINER or INVOKER.
• CHARACTER_SET_CLIENT: The session value of the character_set_client system variable when the view was created.
• COLLATION_CONNECTION: The session value of the collation_connection system variable when the view was created.

STATISTICS Table

Obtain detailed information about database table indexes and statistics. For example, you can check whether an index is unique, understand the order of columns within an index, and estimate the number of unique values in an index.

• TABLE_CATALOG: The catalog name of the table (always ‘def’).
• TABLE_SCHEMA: The name of the database to which the table belongs.
• TABLE_NAME: The name of the table.
• NON_UNIQUE: Indicates whether the index allows duplicate values. If 0, the index is unique.
• INDEX_SCHEMA: The database name to which the index belongs.
• INDEX_NAME: The name of the index.
• SEQ_IN_INDEX: The position of the column within the index.
• COLUMN_NAME: The name of the column.
• COLLATION: The collation of the column.
• CARDINALITY: An estimated count of unique values in the index.
• SUB_PART: The length of the index part. For the entire column, this value is NULL.
• PACKED: Indicates whether compressed storage is used.
• NULLABLE: Indicates whether the column allows NULL values.
• INDEX_TYPE: The index type (e.g., BTREE, HASH, etc.).
• COMMENT: Comment information about the index.

mysql database

Grant system tables

These system tables contain grant information about user accounts and their privileges:

• user: user accounts, global privileges, and other non-privilege columns.
• db: database-level privileges.
• tables_priv: table-level privileges.
• columns_priv: column-level privileges.
• procs_priv: stored procedure and stored function privileges.