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Description

The PostgreSQL error 42P18, 'indeterminate datatype', occurs when the database system cannot unambiguously determine the data type of an expression, a column, or a function argument. This often arises in SQL statements where untyped literals, overloaded functions, or ambiguous type casts lead to confusion for the parser.

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Error Message

indeterminate datatype

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Known Causes

4 known causes

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Untyped Literals in Ambiguous Contexts

PostgreSQL struggles to infer the type of a literal (e.g., a string or number) when its usage context could match multiple data types without an explicit cast.

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Overloaded Functions with Ambiguous Arguments

If a function has multiple definitions (overloads) and the provided arguments' types don't uniquely match one specific overload, the database cannot decide which function to call.

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Ambiguous Type Coercions

This occurs when an expression involves operations between different data types, and PostgreSQL cannot find a clear rule to implicitly convert one type to another without ambiguity.

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NULL in Type-Sensitive Contexts

Using `NULL` in a context where a specific data type is expected (e.g., in `UNION` queries or function arguments) can cause this error if its type cannot be inferred.

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Solutions

3 solutions available

1. Explicitly Cast or Specify Datatype easy

Provide a clear datatype hint to PostgreSQL.

1

Identify the query or statement causing the 'indeterminate datatype' error. This often happens with functions that can return multiple types or with ambiguous literal values.

2

Modify the query to explicitly cast the problematic value or function result to a specific datatype. The most common datatypes to consider are `TEXT`, `VARCHAR`, `INT`, `NUMERIC`, `DATE`, `TIMESTAMP`, etc.

SELECT my_function(some_value)::TEXT;
-- or
SELECT 'some_literal'::INT;

3

If the error occurs in a `CREATE TABLE` or `ALTER TABLE` statement when defining a column or constraint, ensure the datatype for that column or parameter is clearly specified.

CREATE TABLE example (id INT, value JSONB);
-- or
ALTER TABLE example ALTER COLUMN value SET DATA TYPE JSONB;

2. Provide a Typename in a Function Call medium

When using polymorphic functions, specify the expected return type.

1

Locate the function call that is returning the 'indeterminate datatype' error. This often occurs with functions like `array_to_string` or custom polymorphic functions.

2

If the function supports it, provide the desired return type as an argument or hint. For instance, if `array_to_string` is causing issues, you might need to cast the array elements first or use a specific separator.

SELECT array_to_string(ARRAY[1, 2, 3]::TEXT[], ','); -- Explicitly casting array elements
-- or for a custom function that takes a type parameter:
SELECT my_polymorphic_function('some_value', 'INT');

3

Consult the PostgreSQL documentation for the specific function being used to understand how to resolve ambiguity or provide type hints.

3. Ensure Consistent Datatypes in Comparisons medium

Avoid comparing values of different or indeterminate datatypes.

1

Examine `WHERE` clauses or join conditions where you are comparing values. The 'indeterminate datatype' error can arise if PostgreSQL cannot infer a common datatype for comparison.

2

Explicitly cast one or both sides of the comparison to a compatible datatype. For example, if comparing a string literal to a numeric column, cast the literal to the numeric type.

SELECT * FROM my_table WHERE numeric_column = '123'::INT;
-- or if comparing two columns that might be different types:
SELECT * FROM table_a a JOIN table_b b ON a.id::TEXT = b.id::TEXT;

3

If the issue is with string comparisons, ensure you are not accidentally comparing a `VARCHAR` column with a `TEXT` column without explicit casting if there's ambiguity, though PostgreSQL is usually good at this.

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Related Errors

5 related errors

PostgreSQL Error 42P18: Indeterminate Datatype Error