db: Add _or_default variants for column accesses

We were implicitly relying on sqlite3 behavior that returns the zero-value for
nulled fields when accessing them. This adds the same behavior explicitly to
the DB abstraction in order to reduce `db_column_is_null` checks in the logic,
but still make it evident what is happening here.

Fixes https://github.com/fiatjaf/mcldsp/issues/1

Signed-off-by: Christian Decker <@cdecker>

wallet/db.c

@@ -565,6 +565,14 @@ u64 db_column_u64(struct db_stmt *stmt, int col)
 	return stmt->db->config->column_u64_fn(stmt, col);
 }
 
+int db_column_int_or_default(struct db_stmt *stmt, int col, int def)
+{
+	if (db_column_is_null(stmt, col))
+		return def;
+	else
+		return db_column_int(stmt, col);
+}
+
 int db_column_int(struct db_stmt *stmt, int col)
 {
 	return stmt->db->config->column_int_fn(stmt, col);
@@ -1143,6 +1151,16 @@ void *db_column_arr_(const tal_t *ctx, struct db_stmt *stmt, int col,
 	return p;
 }
 
+void db_column_amount_msat_or_default(struct db_stmt *stmt, int col,
+				      struct amount_msat *msat,
+				      struct amount_msat def)
+{
+	if (db_column_is_null(stmt, col))
+		*msat = def;
+	else
+		msat->millisatoshis = db_column_u64(stmt, col); /* Raw: low level function */
+}
+
 void db_column_amount_msat(struct db_stmt *stmt, int col,
 			   struct amount_msat *msat)
 {

wallet/db.h

@@ -159,6 +159,13 @@ struct bitcoin_tx *db_column_tx(const tal_t *ctx, struct db_stmt *stmt, int col)
 void *db_column_arr_(const tal_t *ctx, struct db_stmt *stmt, int col,
 		     size_t bytes, const char *label, const char *caller);
 
+
+/* Some useful default variants */
+int db_column_int_or_default(struct db_stmt *stmt, int col, int def);
+void db_column_amount_msat_or_default(struct db_stmt *stmt, int col,
+				      struct amount_msat *msat,
+				      struct amount_msat def);
+
 /**
  * db_exec_prepared -- Execute a prepared statement
  *

wallet/wallet.c

@@ -1143,14 +1143,14 @@ void wallet_channel_stats_load(struct wallet *w,
 	/* This must succeed, since we know the channel exists */
 	assert(res);
 
-	stats->in_payments_offered = db_column_int(stmt, 0);
-	stats->in_payments_fulfilled = db_column_int(stmt, 1);
-	db_column_amount_msat(stmt, 2, &stats->in_msatoshi_offered);
-	db_column_amount_msat(stmt, 3, &stats->in_msatoshi_fulfilled);
-	stats->out_payments_offered = db_column_int(stmt, 4);
-	stats->out_payments_fulfilled = db_column_int(stmt, 5);
-	db_column_amount_msat(stmt, 6, &stats->out_msatoshi_offered);
-	db_column_amount_msat(stmt, 7, &stats->out_msatoshi_fulfilled);
+	stats->in_payments_offered = db_column_int_or_default(stmt, 0, 0);
+	stats->in_payments_fulfilled = db_column_int_or_default(stmt, 1, 0);
+	db_column_amount_msat_or_default(stmt, 2, &stats->in_msatoshi_offered, AMOUNT_MSAT(0));
+	db_column_amount_msat_or_default(stmt, 3, &stats->in_msatoshi_fulfilled, AMOUNT_MSAT(0));
+	stats->out_payments_offered = db_column_int_or_default(stmt, 4, 0);
+	stats->out_payments_fulfilled = db_column_int_or_default(stmt, 5, 0);
+	db_column_amount_msat_or_default(stmt, 6, &stats->out_msatoshi_offered, AMOUNT_MSAT(0));
+	db_column_amount_msat_or_default(stmt, 7, &stats->out_msatoshi_fulfilled, AMOUNT_MSAT(0));
 	tal_free(stmt);
 }