PostgreSQL 9.5alpha1 Documentation
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# F.40. tsm_system_rows

The `tsm_system_rows` module provides the tablesample method `SYSTEM_ROWS`, which can be used inside the `TABLESAMPLE` clause of a `SELECT`.

This tablesample method uses a linear probing algorithm to read sample of a table and uses actual number of rows as limit (unlike the `SYSTEM` tablesample method which limits by percentage of a table).

## F.40.1. Examples

Here is an example of selecting sample of a table with `SYSTEM_ROWS`. First install the extension:

    CREATE EXTENSION tsm_system_rows;

Then you can use it in `SELECT` command same way as other tablesample methods:

    SELECT * FROM my_table TABLESAMPLE SYSTEM_ROWS(100);

The above command will return a sample of 100 rows from the table my_table (less if the table does not have 100 visible rows).

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