db: Add DB-specific db_last_insert_id

This is likely the last part we need to completely encapsulate the part of the
sqlite3 API that we were using. Like the `db_count_changes` call I decided to
pass in the `struct db_stmt` since really they refer to the statement that was
executed and not the db.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

wallet/db.c

@@ -645,6 +645,17 @@ size_t db_count_changes(struct db_stmt *stmt)
 	return stmt->db->config->count_changes_fn(stmt);
 }
 
+u64 db_last_insert_id_v2(struct db_stmt *stmt TAKES)
+{
+	u64 id;
+	id = stmt->db->config->last_insert_id_fn(stmt);
+
+	if (taken(stmt))
+		tal_free(stmt);
+
+	return id;
+}
+
 bool db_select_step_(const char *location, struct db *db, struct sqlite3_stmt *stmt)
 {
 	int ret;

wallet/db.h

@@ -313,6 +313,7 @@ void db_close(struct db *db);
 bool db_exec_prepared_v2(struct db_stmt *stmt TAKES);
 bool db_query_prepared(struct db_stmt *stmt);
 size_t db_count_changes(struct db_stmt *stmt);
+u64 db_last_insert_id_v2(struct db_stmt *stmt);
 struct db_stmt *db_prepare_v2_(const char *location, struct db *db,
 			       const char *query_id);
 #define db_prepare_v2(db,query) \

wallet/db_common.h

@@ -123,6 +123,7 @@ struct db_config {
 	const unsigned char *(*column_text_fn)(struct db_stmt *stmt, int col);
 	s64 (*column_int_fn)(struct db_stmt *stmt, int col);
 
+	u64 (*last_insert_id_fn)(struct db_stmt *stmt);
 	size_t (*count_changes_fn)(struct db_stmt *stmt);
 
 	bool (*setup_fn)(struct db *db);

wallet/db_sqlite3.c

@@ -188,6 +188,12 @@ static void db_sqlite3_close(struct db *db)
 	sqlite3_close(db->sql);
 }
 
+static u64 db_sqlite3_last_insert_id(struct db_stmt *stmt)
+{
+	sqlite3 *s = stmt->db->conn;
+	return sqlite3_last_insert_rowid(s);
+}
+
 struct db_config db_sqlite3_config = {
 	.name = "sqlite3",
 	.queries = db_sqlite3_queries,
@@ -207,6 +213,7 @@ struct db_config db_sqlite3_config = {
 	.column_blob_fn = &db_sqlite3_column_blob,
 	.column_text_fn = &db_sqlite3_column_text,
 
+	.last_insert_id_fn = &db_sqlite3_last_insert_id,
 	.count_changes_fn = &db_sqlite3_count_changes,
 	.setup_fn = &db_sqlite3_setup,
 	.teardown_fn = &db_sqlite3_close,