Global SysCache Feature Functions

The current feature is a lab feature. Contact Huawei technical support before using it.

• gs_gsc_table_detail(database_id default NULL, rel_id default NULL)

  Description: Queries global system cache table metadata in a database. The user who calls this function must have the SYSADMIN permission.

  Parameter: Specifies the database and table whose global system cache is to be queried. The default value of database_id is NULL or –1, indicating all databases. The value 0 indicates a shared table. Other values indicate the specified database and shared table. rel_id indicates the OID of the specified table. The default value NULL or –1 indicates all tables. Other values indicate the specified table. If the table does not exist, an error is reported. If the OID does not exist, a null result is returned.

  Return type: Tuple

  Example:

  select * from gs_gsc_table_detail(-1) limit 1;
  database_oid | database_name | reloid |         relname         | relnamespace | reltype | reloftype | relowner | relam | relfilenode | reltablespace | relhasindex | relisshared | relkind | relnatts | relhasoids | relhaspkey | parttype | tdhasuids | attnames  | extinfo
  --------------+---------------+--------+-------------------------+--------------+---------+-----------+----------+-------+-------------+---------------+-------------+-------------+---------+----------+------------+------------+----------+-----------+-----------+---------
  0 |               |   2676 | pg_authid_rolname_index |           11 |       0 |         0 |       10 |   403 |           0 |          1664 | f           | t           | i       |        1 | f          | f          | n        | f         | 'rolname' |
  (1 row)

• gs_gsc_catalog_detail(database_id default NULL, rel_id default NULL)

  Description: Queries the system table row information cached in the global system in a database. The user who calls this function must have the SYSADMIN permission.

  Parameter: Specifies the database and table whose global system cache is to be queried. The default value of database_id is NULL or –1, indicating all databases. The value 0 indicates a shared table. Other values indicate the specified database and shared table. rel_id indicates the ID of the specified table, including all system catalogs that have system caches. The default value NULL or –1 indicates all tables. Other values indicate the specified table. If the database does not exist, an error is reported. If the table does not exist, a null result is returned.

  Return type: Tuple

  Example:

  openGauss=# 
  select * from gs_gsc_catalog_detail(16574, 1260);
   database_id | database_name | rel_id | rel_name  | cache_id |  self  |  ctid  | infomask | infomask2 | hash_value | refcount
  -------------+---------------+--------+-----------+----------+--------+--------+----------+-----------+------------+----------
             0 |               |   1260 | pg_authid |       10 | (0, 9) | (0, 9) |    10507 |        26 |  531311568 |       10
             0 |               |   1260 | pg_authid |       11 | (0, 4) | (0, 4) |     2313 |        26 |  365368336 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 9) | (0, 9) |    10507 |        26 | 3911517328 |       10
             0 |               |   1260 | pg_authid |       11 | (0, 7) | (0, 7) |     2313 |        26 | 1317799983 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 5) | (0, 5) |     2313 |        26 | 3664347448 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 1) | (0, 1) |     2313 |        26 |  276477273 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 3) | (0, 3) |     2313 |        26 | 2465837659 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 8) | (0, 8) |     2313 |        26 | 3205288035 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 6) | (0, 6) |     2313 |        26 |  131811687 |        1
             0 |               |   1260 | pg_authid |       11 | (0, 2) | (0, 2) |     2313 |        26 | 1226484587 |        1
  (10 rows)

• gs_gsc_clean(database_id default NULL)

  Description: Clears the global syscache cache. Note that data in use will not be cleared. The user who calls this function must have the SYSADMIN permission.

  Parameter: Specifies the database whose global system cache needs to be cleared. The default value NULL or –1 indicates that the global system cache of all databases is cleared. The value 0 indicates that the global system cache of only the shared table is cleared. Other values indicate that the global system cache of the specified database and shared table is cleared. If the database does not exist, an error is reported.

  Return type: Boolean

  Example:

  openGauss=# select * from gs_gsc_clean();
  gs_gsc_clean
  --------------
  t
  (1 row)

• gs_gsc_dbstat_info(database_id default NULL)

  Description: Obtains GSC memory statistics on the local node, including cache query, hit, loading, expiration, and occupied space information of tuples, relationships, and partitions, database-level elimination information, thread reference information, and memory usage information. This parameter can be used to locate performance problems. For example, if the value of the hits/searches array is far less than 1, the value of global_syscache_threshold may be too small. As a result, the query hit ratio decreases. The user who calls this function must have the SYSADMIN permission.

  Parameter: Specifies the global system cache statistics of the database to be queried. NULL or –1 indicates that all databases are queried. 0 indicates that only the information about the shared table is queried. Other values indicate that the information about the specified database and shared table is queried. Invalid input value. If the database does not exist, an error is reported.

  Return type: Tuple

  Example:

  openGauss=# select * from gs_gsc_dbstat_info();
  database_id | database_name | tup_searches | tup_hits | tup_miss | tup_count | tup_dead | tup_memory | rel_searches | rel_hits | rel_mis
  s | rel_count | rel_dead | rel_memory | part_searches | part_hits | part_miss | part_count | part_dead | part_memory | total_memory | swa
  pout_count | refcount
  -------------+---------------+--------------+----------+----------+-----------+----------+------------+--------------+----------+--------
  --+-----------+----------+------------+---------------+-----------+-----------+------------+-----------+-------------+--------------+----
  -----------+----------
             0 |               |          300 |      235 |       31 |        22 |        2 |       9752 |          598 |      108 |       1
  8 |        18 |        0 |      77720 |             0 |         0 |         0 |          0 |         0 |           0 |       752912 |
           0 |        0
         16574 | postgres      |         3368 |     2289 |      329 |       273 |        0 |      92593 |         1113 |      524 |       4
  8 |        48 |        0 |     340456 |             0 |         0 |         0 |          0 |         0 |           0 |      4124792 |
           0 |       10
  (2 rows)