PG_CLASS
PG_CLASS records database objects and their relationship.
Table 1 PG_CLASS columns
Data type that corresponds to the table's row type. The index is 0 because the index does not have PG_TYPE records. | ||
Access method used, such as B-tree and hash, if this is an index | ||
Name of the on-disk file of this relationship (0 if such file does not exist) | ||
Tablespace in which this relationship is stored. If the value is 0, the default tablespace in this database is used. This column is meaningless if the relationship has no on-disk file. | ||
Size of the on-disk representation of the table in pages (of size BLCKSZ). This is only an estimate used by the optimizer. | ||
Number of rows in the table. This is only an estimate used by the optimizer. | ||
Number of pages marked as all visible in the table. This column is used by the optimizer for optimizing SQL execution. It is updated by VACUUM, ANALYZE, and a few DDL statements such as CREATE INDEX. | ||
OID of the TOAST table associated with the table (0 if no TOAST table exists). The TOAST table stores large columns "offline" in a secondary table. | ||
OID of the index for a TOAST table (0 for a table other than a TOAST table) | ||
Delta tables are attached to column-store tables. They store long tail data generated during storage data import. | ||
OID of a CU description table. CU description tables (Desc tables) belong to column-store tables. They control whether storage data in the HDFS table directory is visible. | ||
Its value is true if this column is a table and has (or recently had) at least one index. It is set by CREATE INDEX but is not immediately cleared by DROP INDEX. If the VACUUM process detects that a table has no index, it clears the relhasindex column and sets the value to false. | ||
Its value is true if the table is shared across all database nodes in openGauss. Only certain system catalogs (such as PG_DATABASE) are shared. | ||
Number of user columns in the relationship (excluding system columns). PG_ATTRIBUTE has the same number of rows as the user columns. | ||
Number of check constraints in the table. For details, see the system catalog PG_CONSTRAINT. | ||
Its value is true if an OID is generated for each row of the relationship. | ||
Its value is true if the table has (or once had) a primary key. | ||
Its value is true if the table has rules. For details, see the system catalog PG_REWRITE. | ||
The value is true if the table has (or once had) triggers. Triggers of the table and view are recorded in the system catalog PG_TRIGGER. | ||
Its value is true if the table has (or once had) any inheritance child table. | ||
All transaction IDs before this one have been replaced with a permanent ("frozen") transaction ID in the table. This column is used to track whether the table needs to be vacuumed to prevent transaction ID wraparound (or to allow PG_CLOG to be shrunk). The value is 0 (InvalidTransactionId) if the relationship is not a table. To ensure forward compatibility, this column is reserved. The relfrozenxid64 column is added to record the information. | ||
The command output of the query is as follows: rolename=xxxx/yyyy --Assigning permissions to a role =xxxx/yyyy --Assigning the permission to public xxxx indicates assigned permissions, and yyyy indicates roles with the assigned permissions. For details on permission descriptions, see Table 2. | ||
Index access method, using character strings in the format of "keyword=value" | ||
All transaction IDs before this one have been replaced with a permanent ("frozen") transaction ID in the table. This column is used to track whether the table needs to be vacuumed to prevent transaction ID wraparound (or to allow PG_CLOG to be shrunk). The value is 0 (InvalidTransactionId) if the relationship is not a table. | ||
Table 2 Description of permissions