How to diagnose and fix the 2203A sql_json_member_not_found error code in Postgres.

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The 2203A error code in PostgreSQL, which corresponds to sql_json_member_not_found, occurs when an attempt is made to access a member of a JSON object that does not exist. This error is part of the SQL standard’s conventions for “SQLSTATE” codes, which PostgreSQL adheres to.

To diagnose and fix this error, you would need to ensure that the JSON data you are querying contains the member you are trying to access. Here are some examples and sample code to illustrate common scenarios and their solutions.

Example 1: Accessing a Non-existent Key

Problem:

SELECT my_json_data->>'non_existent_key' FROM my_table;

If my_json_data does not contain the key non_existent_key, this query will raise the 2203A error.

Fix:

Ensure that the key exists in the JSON data or handle the case where the key might not exist:

SELECT COALESCE(my_json_data->>'existing_key', 'default_value') FROM my_table;

Example 2: Using JSON Functions Incorrectly

Problem:

SELECT jsonb_array_element_text(my_json_data, 'non_existent_key') FROM my_table;

If my_json_data is not an array or the key does not exist, this will raise an error.

Fix:

Make sure you are using the correct function for the data type and that the key exists:

SELECT jsonb_object_field_text(my_json_data, 'existing_key') FROM my_table;

Example 3: Querying JSON Array Elements by Index

Problem:

SELECT my_json_data->>3 FROM my_table; -- Assuming my_json_data is a JSON array

If the array does not have an element at index 3 (0-based index), this will raise the 2203A error.

Fix:

Check the length of the array before attempting to access an index, or handle the error:

SELECT CASE WHEN jsonb_array_length(my_json_data) > 3 THEN my_json_data->>3 ELSE 'default_value' END FROM my_table;

Example 4: Nested JSON Objects

Problem:

SELECT my_json_data->'nested'->>'non_existent_key' FROM my_table;

If the nested object does not contain the non_existent_key, this will raise the error.

Fix:

Verify the structure of the nested JSON object and ensure the key exists:

SELECT my_json_data->'nested'->>'existing_key' FROM my_table;

In all cases, handling the potential absence of a JSON member should be part of your application logic. You can use functions like COALESCE, jsonb_typeof, or conditional statements to provide default values or to skip over missing keys gracefully.

For more detailed information on handling JSON in PostgreSQL, you can refer to the official PostgreSQL Documentation.

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