How to diagnose and fix the 22033 invalid_sql_json_subscript error code in Postgres.

The 22033 invalid_sql_json_subscript error in PostgreSQL occurs when there is an issue with the subscript (indexing) used in a JSON or JSONB column. This error typically happens when you attempt to access an element of a JSON array or object using an invalid index or key. Here’s how to diagnose and fix this error with examples and sample code:

  1. Check Array Bounds: Ensure that you are not trying to access an array element outside of its bounds. JSON arrays in PostgreSQL are zero-indexed. -- Bad Example: Trying to access the 5th element in a 4-element array SELECT '["a", "b", "c", "d"]'::jsonb -> 4; -- Good Example: Accessing the 4th element (index 3) in a 4-element array SELECT '["a", "b", "c", "d"]'::jsonb -> 3;
  2. Correct Data Type: Make sure you are using the correct subscript type for the JSON data. Use integer subscripts for arrays and text subscripts for JSON objects. -- Bad Example: Using integer to access object field SELECT '{"a": 1, "b": 2}'::jsonb -> 1; -- Good Example: Using text to access object field SELECT '{"a": 1, "b": 2}'::jsonb -> 'b';
  3. Existence of Key: When accessing a JSON object, ensure that the key you are trying to access exists. -- Bad Example: Key 'c' does not exist SELECT '{"a": 1, "b": 2}'::jsonb -> 'c'; -- Good Example: Key 'a' exists SELECT '{"a": 1, "b": 2}'::jsonb -> 'a';
  4. Nested Structures: When dealing with nested JSON structures, ensure that you navigate the hierarchy correctly. -- Bad Example: Incorrect path to nested element SELECT '{"a": {"b": {"c": 3}}}'::jsonb -> 'a' -> 'c'; -- Good Example: Correct path to nested element SELECT '{"a": {"b": {"c": 3}}}'::jsonb -> 'a' -> 'b' -> 'c';
  5. Use JSONB Array Elements Function: If you need to access all elements of a JSONB array, use the jsonb_array_elements_text function to expand the JSONB array to a set of text values. SELECT value FROM jsonb_array_elements_text('["a", "b", "c", "d"]'::jsonb);
  6. Use Proper Operators: PostgreSQL provides specific operators for JSON and JSONB types. Use -> for getting a JSON object field by key or a JSON array element by index (as text), and ->> for getting a JSON object field by key or a JSON array element by index (as text). -- Accessing object field as text SELECT '{"a": 1, "b": 2}'::jsonb ->> 'b'; -- Accessing array element as text SELECT '["a", "b", "c", "d"]'::jsonb ->> 3;
  7. Update JSON Values: If you are trying to update a specific index in a JSON array, make sure that you construct the new JSON correctly. -- Bad Example: Trying to set an array element using incorrect syntax UPDATE your_table SET your_column = your_column -> 3 = '"newValue"' WHERE id = your_id; -- Good Example: Using jsonb_set to update an array element UPDATE your_table SET your_column = jsonb_set(your_column, '{3}', '"newValue"', true) WHERE id = your_id;

When you encounter the 22033 invalid_sql_json_subscript error, review your JSON or JSONB data structure and the way you’re trying to access it. Ensure that your subscripts are valid and appropriate for the data types and structures you are working with. If necessary, consult the PostgreSQL documentation for JSON functions and operators to help you construct the correct queries.

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