49.48. pg_tabesample_method

The catalog pg_tablesample_method stores information about table sampling methods which can be used in TABLESAMPLE clause of a SELECT statement.

Table 49-48. pg_tablesample_method Columns

NameTypeReferencesDescription
oidoid Row identifier (hidden attribute; must be explicitly selected)
tsmnamename Name of the sampling method
tsmseqscanbool If true, the sampling method scans the whole table sequentially.
tsmpagemodebool If true, the sampling method always reads the pages completely.
tsminitregprocpg_proc.oid"Initialize the sampling scan" function
tsmnextblockregprocpg_proc.oid"Get next block number" function
tsmnexttupleregprocpg_proc.oid"Get next tuple offset" function
tsmexaminetupleregprocpg_proc.oidFunction which examines the tuple contents and decides if to return it, or zero if none
tsmendregprocpg_proc.oid"End the sampling scan" function
tsmresetregprocpg_proc.oid"Restart the state of sampling scan" function
tsmcostregprocpg_proc.oidCosting function