Function write_export 

pub fn write_export<W: Write>(
    writer: &mut W,
    right_path: &Path,
    left: &DatabaseSummary,
    right: &DatabaseSummary,
    schema_diff: &SchemaDiff,
    data_diffs: &[TableDataDiff],
) -> Result<()>

Writes a SQL migration script to any Write sink, streaming one statement at a time.

This is the bounded-memory export path. Table seeding rows are streamed from disk rather than materialized into a full in-memory collection, and each SQL statement is flushed individually.