overview.md

Overview

INFORMATION_SCHEMA provides access to system metadata, such as the name of a database or table, the data type of a column, etc. GreptimeDB also provides some custom INFORMATION_SCHEMA tables to query metadata about the GreptimeDB system itself, cluster information, and runtime telemetry for example.

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

There is still lots of work to do for INFORMATION_SCHEMA. The tracking issue for INFORMATION_SCHEMA.

Tables for MySQL compatibility

Table Name	Description
CHARACTER_SETS	provides information about available character sets.
CHECK_CONSTRAINTS	Not implemented. Returns zero rows.
COLLATIONS	Provides a list of collations that the server supports.
COLLATION_CHARACTER_SET_APPLICABILITY	Explains which collations apply to which character sets.
COLUMNS	Provides a list of columns for all tables.
COLUMN_PRIVILEGES	Not implemented. Returns zero rows.
COLUMN_STATISTICS	Not supported.
ENGINES	Provides a list of supported storage engines.
EVENTS	Not implemented. Returns zero rows.
FILES	Not implemented. Returns zero rows.
GLOBAL_STATUS	Not implemented. Returns zero rows.
GLOBAL_VARIABLES	Not supported.
KEY_COLUMN_USAGE	Describes the key constraints of the columns, such as the primary key, and time index constraint.
OPTIMIZER_TRACE	Not implemented. Returns zero rows.
PARAMETERS	Not implemented. Returns zero rows.
PARTITIONS	Provides a list of table partitions.
PLUGINS	Not supported.
PROCESSLIST	Not supported.
PROFILING	Not implemented. Returns zero rows.
REFERENTIAL_CONSTRAINTS	Not implemented. Returns zero rows.
ROUTINES	Not implemented. Returns zero rows.
SCHEMATA	Provides similar information to SHOW DATABASES.
SCHEMA_PRIVILEGES	Not implemented. Returns zero rows.
SESSION_STATUS	Not implemented. Returns zero rows.
SESSION_VARIABLES	Not supported.
STATISTICS	Not supported.
TABLES	Provides a list of tables that the current user has visibility of. Similar to SHOW TABLES.
TABLESPACES	Not supported.
TABLE_PRIVILEGES	Not implemented. Returns zero rows.
TRIGGERS	Not implemented. Returns zero rows.
USER_ATTRIBUTES	Not supported.
USER_PRIVILEGES	Not supported.
VARIABLES_INFO	Not supported.
VIEWS	Not supported.

Tables that GreptimeDB provides

Table Name	Description
BUILD_INFO	Provides the system build info.
REGION_PEERS	Provides details about where regions are stored.
RUNTIME_METRICS	Provides the system runtime metrics.
CLUSTER_INFO	Provides the topology information of the cluster.