How to diagnose and fix the 22022 indicator_overflow error code in Postgres.

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The 22022 error code in PostgreSQL, referred to as “indicator_overflow,” occurs when a host variable that is supposed to store a null indicator for an output column is not large enough to hold the value -1, which PostgreSQL uses to signify a null value.

To diagnose and fix this error, you should:

  1. Check Host Language Integration: This error is often related to the interface between PostgreSQL and a host language, such as C, where indicator variables are used to handle NULL values from the database. Make sure that the variable intended to hold the null indicator is of a sufficient data type that can store the value -1.
  2. Review Database Driver Documentation: If you’re using a database driver or an ORM, check the documentation for any known issues or requirements for handling NULL values and indicator variables.
  3. Examine Application Code: In your application code, look for any instances where you’re fetching data from PostgreSQL and expecting a NULL. Ensure that the corresponding indicator variable is properly defined and capable of holding the required value.

Here are some hypothetical examples of how to avoid the 22022 error:

  • Correct Indicator Variable Declaration in C:
  SQLINTEGER indicator;
  SQLRETURN ret;
  ret = SQLGetData(statementHandle, columnNumber, SQL_C_CHAR, &dataBuffer, sizeof(dataBuffer), &indicator);
  if (indicator == SQL_NULL_DATA) {
    // Handle NULL value
  }

In this C code, the indicator variable is of type SQLINTEGER, which is capable of storing the value -1.

  • Proper Handling in a PL/pgSQL Function:
  CREATE OR REPLACE FUNCTION get_nullable_value() RETURNS TABLE (id INT, value TEXT) AS $$
  DECLARE
    indicator INTEGER;
  BEGIN
    -- Assuming 'my_table' has a nullable 'value' column
    FOR id, value IN SELECT id, value FROM my_table LOOP
      IF value IS NULL THEN
        indicator := -1;
        -- Handle the NULL value case
      ELSE
        indicator := 0;
        -- Handle the non-NULL value case
      END IF;
      RETURN NEXT;
    END LOOP;
  END;
  $$ LANGUAGE plpgsql;

In this PL/pgSQL function, the indicator variable is an integer that can store the -1 value for null indication.

It’s important to note that the 22022 error code is less common in high-level programming environments that automatically handle null indicators, and is more likely to be encountered when working directly with SQL in a lower-level programming context.

For further information on PostgreSQL error codes, you can refer to the PostgreSQL documentation on error codes.

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