lib-storage: Preserve messages' vsize record when rebuilding index

Since vsize is often used by quota, losing this can be very expensive.
If the vsize is wrong, it gets fixed automatically when fetching the
message body.

src/lib-storage/index/index-rebuild.c

@@ -8,6 +8,22 @@
 #include "index-storage.h"
 #include "index-rebuild.h"
 
+static void
+index_index_copy_vsize(struct index_rebuild_context *ctx,
+		       struct mail_index_view *view,
+		       uint32_t old_seq, uint32_t new_seq)
+{
+	const void *data;
+	bool expunged;
+
+	mail_index_lookup_ext(view, old_seq, ctx->box->mail_vsize_ext_id,
+			      &data, &expunged);
+	if (data != NULL && !expunged) {
+		mail_index_update_ext(ctx->trans, new_seq,
+				      ctx->box->mail_vsize_ext_id, data, NULL);
+	}
+}
+
 static void
 index_index_copy_cache(struct index_rebuild_context *ctx,
 		       struct mail_index_view *view,
@@ -70,6 +86,7 @@ index_index_copy_from_old(struct index_rebuild_context *ctx,
 	modseq = mail_index_modseq_lookup(view, old_seq);
 	mail_index_update_modseq(ctx->trans, new_seq, modseq);
 
+	index_index_copy_vsize(ctx, view, old_seq, new_seq);
 	index_index_copy_cache(ctx, view, old_seq, new_seq);
 }