PostgreSQL 9.5alpha1 Documentation
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# 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

Name | Type | References | Description
--- | --- | --- | ---
`oid` | `oid` |  | Row identifier (hidden attribute; must be explicitly selected)
`tsmname` | `name` |  | Name of the sampling method
`tsmseqscan` | `bool` |  | If true, the sampling method scans the whole table sequentially.
`tsmpagemode` | `bool` |  | If true, the sampling method always reads the pages completely.
`tsminit` | `regproc` | ``pg_proc`.oid` | "Initialize the sampling scan" function
`tsmnextblock` | `regproc` | ``pg_proc`.oid` | "Get next block number" function
`tsmnexttuple` | `regproc` | ``pg_proc`.oid` | "Get next tuple offset" function
`tsmexaminetuple` | `regproc` | ``pg_proc`.oid` | Function which examines the tuple contents and decides if to return it, or zero if none
`tsmend` | `regproc` | ``pg_proc`.oid` | "End the sampling scan" function
`tsmreset` | `regproc` | ``pg_proc`.oid` | "Restart the state of sampling scan" function
`tsmcost` | `regproc` | ``pg_proc`.oid` | Costing function

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