Appender AppendRow

[loicalleyne]

Would the DuckDB's underlying C API support sending the entire row's data as a struct or map instead of breaking it down to its individual fields as is currently the case with AppendRow?

I'm dealing with several sources of nested data with a dozen or more columns each and would prefer to just pass one struct. I suppose it would involve somehow 'walking the struct' and make a slice of driver.Value to pass to AppendRow.

[taniabogatsch]

Hi @loicalleyne - I've been working on adding support for this to the C API. Here's a list of related PRs. We can start implementing the Go side once go-duckdb moves to the newest duckdb version. :)

• [C API] Implement AddColumn and ClearColumns for the Appender duckdb/duckdb#14880: This allows appending a 'row with gaps', i.e., you are only passing 2 out of 10 columns, and the Appender will then create a data chunk with only these two. Internally, it will fill all other columns with NULL or their default value.
• Try auto-casting for mismatching data chunks in the Appender API duckdb/duckdb#14433: Implicit casting if the values passed via AppendRow don't perfectly match the column.
• [C API] Add table_description_create_ext and table_description_get_column_name duckdb/duckdb#14285: this might be the most interesting for you. It allows one to get the column names of the respective table. Together with the other PRs, this allows to:

Pass, e.g., a map[string]interface{} to AppendRow. It then matches the map keys to the respective columns and appends the values. It should also be possible to omit specific columns or auto-cast if the value type in the map does not perfectly align with the table's column type.

[taniabogatsch]

make a slice of driver.Value to pass to AppendRow

This should already be possible to implement, as AppendRow calls into appendRowSlice, which we could expose. 🤔

// AppendRow loads a row of values into the appender. The values are provided as separate arguments.
func (a *Appender) AppendRow(args ...driver.Value) error {
	// ...
	err := a.appendRowSlice(args)
	// ...
}

// ...

func (a *Appender) appendRowSlice(args []driver.Value) error {
// ...