PostgreSQL cannot determine the data type of a parameter or value in your query. This typically occurs with untyped parameters, NULL values, or ambiguous function calls. Fix by adding explicit type casts using the :: operator.
The "Indeterminate datatype" error (SQLSTATE 42P18) occurs when PostgreSQL's query planner cannot infer a concrete data type for a placeholder, NULL value, or expression in your SQL query. This happens before the query executes, during the planning phase. The error message typically reads "could not determine data type of parameter $1" or similar. PostgreSQL requires clear type information to generate an efficient query plan, and when that information is ambiguous or missing, it stops and returns this error.
When using prepared statements or parameterized queries, explicitly cast parameters to the correct type using the :: operator.
Before (fails):
PREPARE myplan AS SELECT * FROM users WHERE created_at = $1;
EXECUTE myplan(NULL);After (works):
PREPARE myplan AS SELECT * FROM users WHERE created_at = $1::timestamp;
EXECUTE myplan(NULL);In application code with parameterized queries, specify the type:
Node.js/pg example:
const query = "SELECT * FROM users WHERE id = $1::integer";
await client.query(query, [userId]);NULL without a type is ambiguous. Always cast NULL when used in queries.
Before (fails):
SELECT NULL FROM users;
SELECT CASE WHEN active THEN NULL ELSE username END FROM users;After (works):
SELECT NULL::text FROM users;
SELECT CASE WHEN active THEN NULL::text ELSE username END FROM users;For INSERT with partial columns:
INSERT INTO users (name, email) VALUES ($1, NULL::varchar);UNION requires all columns to have compatible types. Cast columns to match.
Before (fails):
SELECT NULL FROM table1
UNION
SELECT username FROM table2;After (works):
SELECT NULL::text FROM table1
UNION
SELECT username FROM table2;Or explicitly cast both sides:
SELECT id::bigint FROM table1
UNION
SELECT id::bigint FROM table2;IN clauses and array constructors need consistent types.
Before (fails):
SELECT * FROM products WHERE id IN (NULL, 123, 456);
SELECT * FROM logs WHERE data IN ('text', NULL);After (works):
SELECT * FROM products WHERE id IN (NULL::integer, 123, 456);
SELECT * FROM logs WHERE data IN ('text'::text, NULL::text);For arrays:
SELECT * FROM table WHERE id = ANY(ARRAY[NULL, 1, 2]::integer[]);Some PostgreSQL functions have multiple versions. Cast arguments to disambiguate.
Before (fails):
SELECT CONCAT(NULL, 'text');
SELECT array_agg(column) FROM table;After (works):
SELECT CONCAT(NULL::text, 'text');
SELECT array_agg(column::text) FROM table;Check the function signature:
\df function_nameUse EXPLAIN to understand where the planner fails:
EXPLAIN SELECT * FROM users WHERE status = $1;If you see the indeterminate datatype error in EXPLAIN output, add the cast:
EXPLAIN SELECT * FROM users WHERE status = $1::varchar;For complex queries, isolate the problematic section and apply casts incrementally.
Type inference complexity: PostgreSQL's type system is powerful but sometimes requires explicit guidance. The database can infer types from context in many cases, but when ambiguity exists, explicit casts are required.
Implicit vs explicit casts: PostgreSQL allows automatic casting between some types (implicit casts) but not others. For example, it won't automatically cast unknown to text in all contexts. Use :: for explicit casts.
Client driver considerations: Some drivers (like psycopg2 in Python or pg in Node.js) can infer parameter types on the client side. Ensure your driver is configured to send type information with parameters.
Performance note: Adding type casts doesn't negatively impact performance. The planner uses them to generate better execution plans. Index usage may be preserved depending on the cast target.
Collation and domain types: Be aware that casting can affect collation behavior and won't work for domain-specific types without additional setup. For complex types, consider creating custom casts or using CREATE CAST.
ERROR: syntax error at end of input
Syntax error at end of input in PostgreSQL
Bind message supplies N parameters but prepared statement requires M
Bind message supplies N parameters but prepared statement requires M in PostgreSQL
Multidimensional arrays must have sub-arrays with matching dimensions
Multidimensional arrays must have sub-arrays with matching dimensions
ERROR: value too long for type character varying
Value too long for type character varying
insufficient columns in unique constraint for partition key
How to fix "insufficient columns in unique constraint for partition key" in PostgreSQL