The PostgreSQL error "2202G: invalid_tablesample_repeat" occurs when using the TABLESAMPLE clause with an invalid REPEAT parameter value. This error indicates that the REPEAT parameter provided to the TABLESAMPLE clause is outside the valid range (0 to 2^31-1) or has an incorrect data type.
PostgreSQL's TABLESAMPLE clause allows you to query a random sample of rows from a table. The REPEAT parameter is used to provide a seed value for the random number generator, ensuring reproducible results when running the same query multiple times. The error "2202G: invalid_tablesample_repeat" is raised when PostgreSQL cannot interpret the REPEAT parameter value correctly, either because it's outside the allowed integer range (0 to 2,147,483,647) or because it's not a valid integer at all. This is a data integrity error that prevents the query from executing.
First, examine the query that's failing and identify the REPEAT parameter value:
-- Example of a TABLESAMPLE query with REPEAT
SELECT * FROM users TABLESAMPLE SYSTEM (10) REPEATABLE (12345);
-- The REPEAT parameter is 12345 in this exampleLook for the number after REPEATABLE in your query. This value must be an integer between 0 and 2,147,483,647.
Ensure the REPEAT value is within the valid range (0 to 2,147,483,647):
-- Valid examples:
SELECT * FROM table TABLESAMPLE BERNOULLI (5) REPEATABLE (0); -- Minimum valid
SELECT * FROM table TABLESAMPLE SYSTEM (10) REPEATABLE (1000); -- Typical value
SELECT * FROM table TABLESAMPLE BERNOULLI (15) REPEATABLE (2147483647); -- Maximum valid
-- Invalid examples that cause the error:
SELECT * FROM table TABLESAMPLE SYSTEM (10) REPEATABLE (-1); -- Negative
SELECT * FROM table TABLESAMPLE BERNOULLI (5) REPEATABLE (2147483648); -- Too large
SELECT * FROM table TABLESAMPLE SYSTEM (10) REPEATABLE (NULL); -- NULL
SELECT * FROM table TABLESAMPLE BERNOULLI (5) REPEATABLE ('seed'); -- StringIf you're using a variable or expression for the REPEAT parameter, ensure it evaluates to a valid integer:
-- Problematic: Using a variable that might be invalid
DO $$
DECLARE
my_seed INTEGER := -1; -- This will cause the error
BEGIN
PERFORM * FROM users TABLESAMPLE SYSTEM (10) REPEATABLE (my_seed);
END $$;
-- Solution: Validate and clamp the value
DO $$
DECLARE
my_seed INTEGER := -1;
valid_seed INTEGER;
BEGIN
-- Ensure seed is within valid range
valid_seed := GREATEST(0, LEAST(my_seed, 2147483647));
PERFORM * FROM users TABLESAMPLE SYSTEM (10) REPEATABLE (valid_seed);
END $$;If you need reproducible sampling but can't use a valid REPEAT parameter, consider alternative approaches:
-- Option 1: Use a fixed valid seed
SELECT * FROM users TABLESAMPLE SYSTEM (10) REPEATABLE (123456);
-- Option 2: Use random() with setseed() for custom reproducibility
SELECT setseed(0.12345);
SELECT * FROM users ORDER BY random() LIMIT (SELECT COUNT(*) * 0.1 FROM users);
-- Option 3: Use md5 hash for deterministic sampling
SELECT * FROM users
WHERE (md5(id::text) < '80000000000000000000000000000000')
LIMIT (SELECT COUNT(*) * 0.1 FROM users);After fixing the REPEAT parameter, test your query to ensure it works:
-- Test with a valid REPEAT value
EXPLAIN ANALYZE
SELECT * FROM large_table TABLESAMPLE SYSTEM (5) REPEATABLE (42);
-- Verify it returns consistent results
SELECT COUNT(*) FROM (SELECT * FROM large_table TABLESAMPLE SYSTEM (5) REPEATABLE (42)) s1;
SELECT COUNT(*) FROM (SELECT * FROM large_table TABLESAMPLE SYSTEM (5) REPEATABLE (42)) s2;
-- Both counts should be identical (within sampling variance)Monitor your application to ensure the error no longer occurs.
The REPEAT parameter in TABLESAMPLE uses a 32-bit signed integer range. This limitation comes from PostgreSQL's internal random number generator implementation. For very large sampling operations where you need seeds beyond 2^31-1, consider using application-level sampling or partitioning your data. Note that different TABLESAMPLE methods (SYSTEM vs BERNOULLI) may have different performance characteristics when used with REPEATABLE. The REPEATABLE clause ensures that consecutive executions of the same query with the same seed return the same sample, which is crucial for reproducible data analysis and testing.
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