PostgreSQL 9.5alpha1 Documentation
Prev | Up | Appendix F. Additional Supplied Modules | Next

# F.41. tsm_system_time

The `tsm_system_time` module provides the tablesample method `SYSTEM_TIME`, 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 time in milliseconds as limit (unlike the `SYSTEM` tablesample method which limits by percentage of a table). This gives you some control over the length of execution of your query.

## F.41.1. Examples

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

    CREATE EXTENSION tsm_system_time;

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

    SELECT * FROM my_table TABLESAMPLE SYSTEM_TIME(1000);

The above command will return as large a sample of my_table as it can read in 1 second (or less if it reads whole table faster).

Prev | Home | Next
tsm_system_rows | Up | unaccent