How to fix PL/pgSQL error in PostgreSQL

PostgreSQLINTERMEDIATEMEDIUMUpdated Dec 28, 2025· 205 views

PL/pgSQL errors occur when stored procedures, functions, or triggers contain syntax errors, type mismatches, or runtime exceptions. Fix them by validating RAISE statement syntax, checking parameter counts, and using GET STACKED DIAGNOSTICS for debugging.

Quick fix

Fixes PL/pgSQL error

-- INCORRECT: 2 placeholders but only 1 argument
RAISE EXCEPTION 'Error: % in %', error_msg;

-- CORRECT: 2 placeholders and 2 arguments
RAISE EXCEPTION 'Error: % in %', error_msg, context_info;

-- Use %% to output a literal percent sign
RAISE NOTICE 'Progress: 100%%';
  1. Verify RAISE statement syntax and parameter count
  2. Check variable declarations and type compatibility
  3. Validate exception handling with correct SQLSTATE codes
  4. Use GET STACKED DIAGNOSTICS only within exception handlers
postgresql — error
-- INCORRECT: 2 placeholders but only 1 argument
RAISE EXCEPTION 'Error: % in %', error_msg;
-- CORRECT: 2 placeholders and 2 arguments
RAISE EXCEPTION 'Error: % in %', error_msg, context_info;
-- Use %% to output a literal percent sign
RAISE NOTICE 'Progress: 100%%';
PL/pgSQL error

What this error means

PL/pgSQL is PostgreSQL's procedural language for writing stored functions, triggers, and blocks. A "PL/pgSQL error" is a generic message that covers various runtime or compilation issues within your stored code. These errors can range from incorrect RAISE statement formatting to unhandled exceptions during function execution. The error typically includes details about the specific problem (syntax error, type mismatch, or uncaught exception) and occurs when PostgreSQL compiles or executes your function body.

Typical symptoms

  • Function creation fails with syntax error during CREATE FUNCTION
  • Function executes but raises "PL/pgSQL error" at a specific line
  • RAISE statement causes "too many parameters" or "too few parameters" error
  • Variable assignments fail with type mismatch errors in function body
  • Exception handling doesn't catch expected errors
  • GET STACKED DIAGNOSTICS unavailable when called outside exception handler

Common causes

  1. RAISE statement has mismatched placeholder count - using % placeholders without matching arguments
  2. Using invalid RAISE syntax - mixing old and new RAISE statement formats incorrectly
  3. Type mismatch in assignments or function parameters within the procedure
  4. Variable declared but not properly scoped or initialized before use
  5. Incorrect exception handling - trying to catch non-existent condition names or invalid SQLSTATE codes
  6. Using GET STACKED DIAGNOSTICS outside an exception handler where it is not valid
  7. Missing required clauses in loop or control flow statements
  8. Referencing undefined variables or columns in function body

How to fix "PL/pgSQL error"

1Verify RAISE statement syntax and parameter count

Check that the number of % placeholders in your RAISE statement matches the number of arguments passed. Each % expects exactly one argument.

sql
-- INCORRECT: 2 placeholders but only 1 argument
RAISE EXCEPTION 'Error: % in %', error_msg;

-- CORRECT: 2 placeholders and 2 arguments
RAISE EXCEPTION 'Error: % in %', error_msg, context_info;

-- Use %% to output a literal percent sign
RAISE NOTICE 'Progress: 100%%';
2Check variable declarations and type compatibility

Ensure all variables are declared with correct types and that assignments match those types. Use explicit casting if needed.

sql
CREATE FUNCTION check_age(user_id INT) RETURNS TEXT AS $$
DECLARE
  age INT;
  message TEXT;
BEGIN
  SELECT user_age INTO age FROM users WHERE id = user_id;
  -- Make sure age is INT and user_age column is compatible
  message := 'User age is ' || age::TEXT;
  RETURN message;
END;
$$ LANGUAGE plpgsql;
3Validate exception handling with correct SQLSTATE codes

Use valid PostgreSQL SQLSTATE codes or condition names in exception handlers. Refer to the error codes appendix for the complete list.

sql
BEGIN
  PERFORM 1 / 0;  -- Will raise division by zero
EXCEPTION
  WHEN division_by_zero THEN
    RAISE NOTICE 'Cannot divide by zero';
  WHEN SQLSTATE '22012' THEN
    RAISE NOTICE 'Caught by SQLSTATE code';
END;
4Use GET STACKED DIAGNOSTICS only within exception handlers

GET STACKED DIAGNOSTICS captures error details and must be called inside a BEGIN...EXCEPTION block.

sql
BEGIN
  -- Some operation that might fail
  INSERT INTO table_name VALUES (NULL);  -- May violate constraint
EXCEPTION
  WHEN OTHERS THEN
    GET STACKED DIAGNOSTICS
      error_code = RETURNED_SQLSTATE,
      error_msg = MESSAGE_TEXT;
    RAISE NOTICE 'Error [%]: %', error_code, error_msg;
END;
5Enable plpgsql.check_asserts for assertion debugging

Use ASSERT statements for inline debugging checks. These can be toggled via configuration.

sql
CREATE FUNCTION validate_amount(amount DECIMAL) RETURNS BOOLEAN AS $$
BEGIN
  ASSERT amount > 0, 'Amount must be positive';
  ASSERT amount <= 1000000, 'Amount exceeds maximum';
  RETURN TRUE;
END;
$$ LANGUAGE plpgsql;

-- Enable assertions (on by default)
SET plpgsql.check_asserts = on;
6Use the plpgsql_check extension for static analysis

Install and use plpgsql_check to catch errors before runtime, including unused variables, type mismatches, and undefined references.

bash
-- Install the extension
CREATE EXTENSION IF NOT EXISTS plpgsql_check;

-- Check a function for errors
SELECT * FROM plpgsql_check_function('my_function(INT)'::regprocedure);

Advanced notes

PostgreSQL error codes follow the SQL standard SQLSTATE format: a five-character code where the first two characters indicate the error class (00-99). Class 00 represents success, 01 represents warnings, and 02 represents "no data". Codes ending in 000 are category codes and catch all errors in that class. When writing functions that will be called frequently, use pgAdmin's PL/pgSQL debugger (requires superuser privileges and shared_preload_libraries configuration) to step through execution. For complex error scenarios, consider using DETAIL and HINT clauses in RAISE EXCEPTION to provide context that helps users understand the root cause: RAISE EXCEPTION 'Invalid input' DETAIL 'Expected integer, got %', typeof(input) HINT 'Check your data types'.

Frequently asked questions

What does "PL/pgSQL error" mean?
PL/pgSQL is PostgreSQL's procedural language for writing stored functions, triggers, and blocks. A "PL/pgSQL error" is a generic message that covers various runtime or compilation issues within your stored code. These errors can range from incorrect RAISE statement formatting to unhandled exceptions during function execution.
How do I fix "PL/pgSQL error"?
PL/pgSQL errors occur when stored procedures, functions, or triggers contain syntax errors, type mismatches, or runtime exceptions. Fix them by validating RAISE statement syntax, checking parameter counts, and using GET STACKED DIAGNOSTICS for debugging.
What causes "PL/pgSQL error"?
RAISE statement has mismatched placeholder count - using % placeholders without matching arguments Using invalid RAISE syntax - mixing old and new RAISE statement formats incorrectly Type mismatch in assignments or function parameters within the procedure
Is the "PL/pgSQL error" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading