How can I differentiate between generic errors and specific conditions like \'database does not exist\' errors using the Postgres driver?

Retrieving Error Codes from Database Operations

When executing queries using the Postgres driver (lib/pq), it is occasionally necessary to distinguish between generic errors and specific conditions such as "database does not exist" errors. To facilitate this, the Postgres driver provides a structured approach for inspecting error details.

Accessing Error Codes

Errors returned by db.Exec(...) are of type *pq.Error, a struct that contains various fields describing the error. To access these fields, use the following syntax:

if err, ok := err.(*pq.Error); ok {
    // Inspect error fields, such as:
    fmt.Println("Error code:", err.Code.Name())
}

Identifying "Database Does Not Exist" Errors

Unfortunately, there is no dedicated error code for "database does not exist" errors. Instead, it falls under the more general "28003: database does not exist" error. To check for this condition, use the following code:

if err, ok := err.(*pq.Error); ok {
    if err.Code.Name() == "28003" {
        // Database does not exist
    }
}

Additional Fields

In addition to the error code, the *pq.Error struct provides other useful fields, including:

• Message: A human-readable error message.
• Severity: The severity of the error, ranging from "NOTICE" to "FATAL."
• Detail: Additional details about the error.
• Hint: A suggestion on how to resolve the error.
• Position: The position in the SQL statement where the error occurred.

By utilizing these fields, developers can gain a deeper understanding of errors encountered during database operations, allowing for more informed error handling and debugging.

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