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. 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).