graph/db: freeze sql migration queries

sqldb/sqlc/db_custom.go

@@ -5,6 +5,12 @@ import (
 	"strings"
 )
 
+// GetTx returns the underlying DBTX (either *sql.DB or *sql.Tx) used by the
+// Queries struct.
+func (q *Queries) GetTx() DBTX {
+	return q.db
+}
+
 // makeQueryParams generates a string of query parameters for a SQL query. It is
 // meant to replace the `?` placeholders in a SQL query with numbered parameters
 // like `$1`, `$2`, etc. This is required for the sqlc /*SLICE:<field_name>*/