All Products
Search
Document Center

Metadatabases and data dictionaries

Last Updated: Dec 09, 2021

The metadatabase of PolarDB-X is the INFORMATION_SCHEMA database that is compatible with the metadatabase of MySQL. To query the metadatabase, you can execute SQL statements over the JDBC connection.

INFORMATION_SCHEMA table

Compatible with the relevant table of PolarDB-X

SCHEMATA

Yes

TABLES

Yes

COLUMNS

Yes

STATISTICS

Yes

COLUMN_STATISTICS

Histogram statistics are in PolarDB-X format.

ENGINES

Yes

KEYWORDS

Yes

COLLATIONS

Yes

TABLE_CONSTRAINTS

Yes

PROCESSLIST

Yes

SESSION_VARIABLES

Yes

GLOBAL_VARIABLES

Yes

INNODB_LOCKS

Yes

INNODB_TRX

Yes

INNODB_BUFFER_PAGE

Yes

INNODB_BUFFER_POOL_STATS

Yes

INNODB_BUFFER_PAGE_LRU

Yes

INNODB_LOCK_WAITS

Yes

USER_PRIVILEGES

Yes

PARTITIONS

Only PolarDB-X partitioned tables are supported.

WORKLOAD

The hybrid transaction/analytical processing (HTAP) workload in PolarDB-X.

GLOBAL_INDEXES

Global secondary indexes in PolarDB-X.

METADATA_LOCK

The information about metadata locks (MDLs) in the PolarDB-X instance.

TABLE_GROUP

The information about table groups in the PolarDB-X instance.

TABLE_DETAIL

The information about each stored partition in partitioned tables in the PolarDB-X instance.

LOCALITY_INFO

The locality information in the PolarDB-X instance.

PHYSICAL_PROCESSLIST

The information about SQL statements from compute nodes to data nodes in the PolarDB-X instance.

PLAN_CACHE

The information about the plan cache in the PolarDB-X instance.

STATISTIC_TASK

The information about the statistics task in the PolarDB-X instance.

CCL_RULE

The information about concurrency control (CCL) rules in the PolarDB-X instance.

CCL_TRIGGER

The information about triggered CCL rules in the PolarDB-X instance.

SCHEMA_PRIVILEGES

No

TABLE_PRIVILEGES

No

INNODB_TEMP_TABLE_INFO

No

INNODB_SYS_INDEXES

No

INNODB_SYS_FIELDS

No

INNODB_CMP_PER_INDEX_RESET

No

INNODB_FT_DEFAULT_STOPWORD

No

INNODB_FT_INDEX_TABLE

No

INNODB_FT_INDEX_CACHE

No

INNODB_SYS_TABLESPACES

No

INNODB_METRICS

No

INNODB_SYS_FOREIGN_COLS

No

INNODB_CMPMEM

No

INNODB_SYS_COLUMNS

No

INNODB_SYS_FOREIGN

No

INNODB_SYS_TABLESTATS

No

INNODB_FT_CONFIG

No

INNODB_SYS_VIRTUAL

No

INNODB_CMP

No

INNODB_FT_BEING_DELETED

No

INNODB_CMP_PER_INDEX

No

INNODB_CMPMEM_RESET

No

INNODB_CMP_RESET

No

INNODB_FT_DELETED

No

INNODB_SYS_TABLES

No

INNODB_SYS_DATAFILES

No

PROFILING

No

REFERENTIAL_CONSTRAINTS

No

SESSION_STATUS

No

TABLESPACES

No

EVENTS

No

TRIGGERS

No

ROUTINES

No

COLUMN_PRIVILEGES

No

FILES

No

KEY_COLUMN_USAGE

No

OPTIMIZER_TRACE

No

PARAMETERS

No

CHARACTER_SETS

No

COLLATION_CHARACTER_SET_APPLICABILITY

No

PLUGINS

No

SCHEMATA

The SCHEMATA table provides the information about databases. The table contains the following columns:

  • CATALOG_NAME: the name of the catalog to which the database belongs. Set the value to def.

  • SCHEMA_NAME: the name of the database.

  • DEFAULT_CHARACTER_SET_NAME: the default name of the character set in the database.

  • DEFAULT_COLLATION_NAME: the default collation name of the database.

  • SQL_PATH: Set the value to NULL.

TABLES

The TABLES table provides the information about database tables. The table contains the following columns:

  • TABLE_CATALOG: the name of the catalog to which the table belongs. Set the value to def.

  • TABLE_SCHEMA: the name of the database to which the table belongs.

  • TABLE_NAME: the name of the table.

  • TABLE_TYPEBASE: the table type. For standard tables, the value is TABLE. For views, the value is VIEW. For INFORMATION_SCHEMA tables, the value is SYSTEM VIEW.

  • ENGINE: the storage engine of the database.

  • VERSION: the version of the database.

  • ROW_FORMAT: the row format.

  • TABLE_ROWS: the estimated number of rows in the table.

  • AVG_ROW_LENGTH: the average row length.

  • DATA_LENGTH: the estimated space of the base table.

  • MAX_DATA_LENGTH: the maximum space of the table. Default value: NULL.

  • INDEX_LENGTH: the estimated space of the index table.

  • DATA_FREE: the idle space of the table.

  • AUTO_INCREMENT: the next AUTO_INCREMENT value.

  • CREATE_TIME: the time when the table was created.

  • UPDATE_TIME: the time when the table was updated.

  • CHECK_TIME: the time when the table was checked. Set the value to NULL.

  • TABLE_COLLATION: the default collation of the table.

  • CHECKSUM: the CHECKSUM value of the table.

  • CREATE_OPTIONS: the options in CREATE TABLE statements.

  • TABLE_COMMENT: the comment used when the table is created.

COLUMNS

The COLUMNS table provides the information about database columns. The table contains the following columns:

  • TABLE_CATALOG: the catalog name of the table to which the column belongs. Set the value to def.

  • TABLE_SCHEMA: the database name of the table to which the column belongs.

  • TABLE_NAME: the name of the table to which the column belongs.

  • COLUMN_NAME: the column name.

  • ORDINAL_POSITION: the position of the column in the table.

  • COLUMN_DEFAULT: the default value of the column.

  • IS_NULLABLE: specifies whether the column can be set to Null.

  • DATA_TYPE: the data type of the column. The value does not contain the precision of the column.

  • CHARACTER_MAXIMUM_LENGTH: the maximum length of the column. Unit: characters.

  • CHARACTER_OCTET_LENGTH: the maximum length of the column. Unit: bytes.

  • NUMERIC_PRECISION: the numeric precision of the column.

  • NUMERIC_SCALE: the numeric scale of the column.

  • DATETIME_PRECISION: the datetime precision of the column.

  • CHARACTER_SET_NAME: the name of the character set for the column.

  • COLLATION_NAME: the collation name of the column.

  • COLUMN_TYPE: the column type. The value contains the precision of the column.

  • COLUMN_KEY: the index information about the column.

  • EXTRA: the additional information about the column.

  • PRIVILEGES: the permissions that are granted to the column.

  • COLUMN_COMMENT: the comment in the column definition.

  • GENERATION_EXPRESSION: the automatically generated column.

STATISTICS

The STATISTICS table provides the information about database indexes. The table contains the following columns:

  • TABLE_CATALOG: the catalog name of the table to which the index belongs. Set the value to def.

  • TABLE_SCHEMA: the schema name of the table to which the index belongs.

  • TABLE_NAME: the name of the table to which the index belongs.

  • NON_UNIQUE: specifies whether the index is unique.

  • INDEX_SCHEMA: the schema name of the table to which the index belongs.

  • INDEX_NAME: the name of the index.

  • SEQ_IN_INDEX: the sequence number of the index to which the column belongs.

  • COLUMN_NAME: the column name.

  • COLLATION: the information about the column collation.

  • CARDINALITY: the value of the cardinality column.

  • SUB_PART: the prefix of the index.

  • PACKED: the information about the compressed index.

  • NULLABLE: specifies whether the column can contain NULL values.

  • INDEX_TYPE: the type of the index.

  • COMMENT: the comment of the index. The comment is not in the form of columns.

  • INDEX_COMMENT: the comment of the index.

For more information about Information_schema tables, visit the MySQL official website.