How Do You Handle Database Non-Existence Errors When Dropping Databases with the PostgreSQL Driver?

Handling Database Non-Existence Errors with db.Exec(...)

When attempting to delete a database with db.Exec("DROP DATABASE dbName;") using the postgres driver (lib/pq), it's helpful to differentiate between expected errors (e.g., "database does not exist") and unexpected errors.

Checking Error Codes

To determine the specific error code returned, it's necessary to inspect the returned error. The lib/pq package returns errors of type *pq.Error, which is a struct. This struct provides access to detailed error information, including the error code.

<code class="go">if err, ok := err.(*pq.Error); ok {
    // Here err is of type *pq.Error and you can inspect its fields
    fmt.Println("pq error code:", err.Code.Name())
}</code>

Error Field Details

The *pq.Error struct has several fields that provide information about the error:

<code class="go">type Error struct {
    Severity         string
    Code             ErrorCode
    Message          string
    Detail           string
    Hint             string
    Position         string
    InternalPosition string
    InternalQuery    string
    Where            string
    Schema           string
    Table            string
    Column           string
    DataTypeName     string
    Constraint       string
    File             string
    Line             string
    Routine          string
}</code>

Database Non-Existence Error Code

Unfortunately, there is no specific error code for "database does not exist" errors in PostgreSQL. Instead, you may encounter errors such as:

• 3D000: Invalid catalog name
• 42P01: Table or view not found

Handling Non-Existence Errors

Since there's no dedicated error code, you may need to manually parse the error message and check for key phrases like "database does not exist" or "table or view not found."

<code class="go">if strings.Contains(err.Message, "database does not exist") {
    // Handle database non-existence error
}</code>

By inspecting the *pq.Error fields and manually parsing the error message, you can effectively handle database non-existence errors and perform the appropriate conditional actions.

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