box: store field def array in read view if field names are enabled

We need field names in the raw read view API (available in EE only).
Currently, we decode the raw format data to create the field def array
for a raw read view space but this looks ugly and complicates the code.
Let's duplicate the field def array stored in the space def instead,
as we used to before commit d8abfe3 ("box: use format data instead
of field def array in space read view").

NO_DOC=internal
NO_TEST=internal
NO_CHANGELOG=internal

Author: locker

src/box/read_view.c

@@ -75,6 +75,8 @@ static void
 space_read_view_delete(struct space_read_view *space_rv)
 {
 	assert(space_rv->format == NULL);
+	if (space_rv->field_count > 0)
+		field_def_array_delete(space_rv->fields, space_rv->field_count);
 	free(space_rv->format_data);
 	for (uint32_t i = 0; i <= space_rv->index_id_max; i++) {
 		struct index_read_view *index_rv = space_rv->index_map[i];
@@ -107,6 +109,15 @@ space_read_view_new(struct space *space, const struct read_view_opts *opts)
 
 	space_rv->id = space_id(space);
 	space_rv->group_id = space_group_id(space);
+	if (opts->enable_field_names && space->def->field_count > 0) {
+		space_rv->fields = field_def_array_dup(space->def->fields,
+						       space->def->field_count);
+		assert(space_rv->fields != NULL);
+		space_rv->field_count = space->def->field_count;
+	} else {
+		space_rv->fields = NULL;
+		space_rv->field_count = 0;
+	}
 	if (opts->enable_field_names &&
 	    space->def->format_data != NULL) {
 		space_rv->format_data = xmalloc(space->def->format_data_len);

src/box/read_view.h

@@ -34,11 +34,17 @@ struct space_read_view {
 	uint32_t id;
 	/** Space name. */
 	char *name;
+	/**
+	 * Tuple field definition array used by this space. Allocated only if
+	 * read_view_opts::enable_field_names is set, otherwise set to NULL.
+	 */
+	struct field_def *fields;
+	/** Number of entries in the fields array. */
+	uint32_t field_count;
 	/**
 	 * Tuple format data used by this space. Allocated only if
 	 * read_view_opts::enable_field_names is set, otherwise set to NULL.
-	 * Used for creation of space_read_view::format and
-	 * box_raw_read_view_space::fields.
+	 * Used for creation of space_read_view::format.
 	 */
 	char *format_data;
 	/** Length of tuple format data. */