tsm_system_rows

tsm_system_rows : TABLESAMPLE method which accepts number of rows as a limit

Overview

ID	Extension	Package	Version	Category	License	Language
4910	tsm_system_rows	tsm_system_rows	`1.0`	FUNC	PostgreSQL	C

Attribute	Has Binary	Has Library	Need Load	Has DDL	Relocatable	Trusted
--s-dt-	No	Yes	No	Yes	no	yes

Relationships
Need By	documentdb
See Also	random permuteseq tsm_system_time pg_crash pg_idkit pgx_ulid pg_uuidv7 pg_hashids

Packages

PG18	PG17	PG16	PG15	PG14
1.0	1.0	1.0	1.0	1.0

This is a built-in contrib extension ship with the PostgreSQL kernel

Install

Create this extension with:

CREATE EXTENSION tsm_system_rows;

Usage

tsm_system_rows: row-count-based TABLESAMPLE method

Provides the SYSTEM_ROWS table sampling method that returns exactly the specified number of rows.

CREATE EXTENSION tsm_system_rows;

TABLESAMPLE Method

SYSTEM_ROWS(count int) – maximum number of rows to return.

Examples

-- Sample exactly 100 rows
SELECT * FROM my_table TABLESAMPLE SYSTEM_ROWS(100);

-- Quick peek at 10 rows from a large table
SELECT * FROM large_table TABLESAMPLE SYSTEM_ROWS(10);

Performs block-level sampling (may exhibit clustering effects with small samples). Returns all rows if the table has fewer rows than requested. Does not support REPEATABLE.

Last updated on 2026-03-12

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