lib-index: Verify that keywords in dovecot.index header don't change unexpectedly

Previously this was behind DEBUG for performance reasons, but that was only
because dovecot.index file used to be modified directly. Nowadays it's rare
that the index is being re-read within the same session (most changes are
read via dovecot.index.log), so it's better to verify that things are
working correctly.

diff --git a/src/lib-index/mail-index-map-hdr.c b/src/lib-index/mail-index-map-hdr.c
index b55c9cf82a97787dc78c7c93abccc6c678765c31..3287a284d25321bf61779f5ca5dcdd5b8102e704 100644 (file)
--- a/src/lib-index/mail-index-map-hdr.c
+++ b/src/lib-index/mail-index-map-hdr.c
@@ -78,6 +78,12 @@ int mail_index_map_parse_keywords(struct mail_index_map *map)
           - struct mail_index_keyword_header
           - struct mail_index_keyword_header_rec * keywords_count
           - const char names[] * keywords_count
+
+          The mail_index_keyword_header_rec are rather unnecessary nowadays.
+          They were originally an optimization when dovecot.index header kept
+          changing constantly, but nowadays the changes are usually read from
+          the .log changes, so re-reading dovecot.index header isn't common.
+          In a later version we could even remove it.
        */
        i_assert(ext->hdr_offset < map->hdr.header_size);
        kw_hdr = MAIL_INDEX_MAP_HDR_OFFSET(map, ext->hdr_offset);
@@ -87,13 +93,6 @@ int mail_index_map_parse_keywords(struct mail_index_map *map)
        old_count = !array_is_created(&map->keyword_idx_map) ? 0 :
                array_count(&map->keyword_idx_map);
 
-       /* Keywords can only be added into same mapping. Removing requires a
-          new mapping (recreating the index file) */
-       if (kw_hdr->keywords_count == old_count) {
-               /* nothing changed */
-               return 0;
-       }
-
        /* make sure the header is valid */
        if (kw_hdr->keywords_count < old_count) {
                mail_index_set_error(index, "Corrupted index file %s: "
@@ -129,14 +128,23 @@ int mail_index_map_parse_keywords(struct mail_index_map *map)
        if (!array_is_created(&map->keyword_idx_map)) 
                i_array_init(&map->keyword_idx_map, kw_hdr->keywords_count);
 
-#ifdef DEBUG
-       /* Check that existing headers are still the same. It's behind DEBUG
-          since it's pretty useless waste of CPU normally. */
+       size_t name_offset = 0;
+       /* Check that existing headers are still the same. */
        for (i = 0; i < array_count(&map->keyword_idx_map); i++) {
                const char *keyword = name + kw_rec[i].name_offset;
                const unsigned int *old_idx;
                unsigned int kw_idx;
 
+               if (kw_rec[i].name_offset != name_offset) {
+                       /* this shouldn't happen, but the old code didn't check
+                          for this so for safety keep this as a warning. */
+                       e_warning(index->event,
+                                 "Corrupted index file %s: "
+                                 "Mismatching keyword name_offset",
+                                 index->filepath);
+               }
+               name_offset += strlen(keyword) + 1;
+
                old_idx = array_idx(&map->keyword_idx_map, i);
                if (!mail_index_keyword_lookup(index, keyword, &kw_idx) ||
                    kw_idx != *old_idx) {
@@ -146,13 +154,23 @@ int mail_index_map_parse_keywords(struct mail_index_map *map)
                        return -1;
                }
        }
-#endif
+
        /* Register the newly seen keywords */
        i = array_count(&map->keyword_idx_map);
        for (; i < kw_hdr->keywords_count; i++) {
                const char *keyword = name + kw_rec[i].name_offset;
                unsigned int kw_idx;
 
+               if (kw_rec[i].name_offset != name_offset) {
+                       /* this shouldn't happen, but the old code didn't check
+                          for this so for safety keep this as a warning. */
+                       e_warning(index->event,
+                                 "Corrupted index file %s: "
+                                 "Mismatching keyword name_offset",
+                                 index->filepath);
+               }
+               name_offset += strlen(keyword) + 1;
+
                if (*keyword == '\0') {
                        mail_index_set_error(index, "Corrupted index file %s: "
                                "Empty keyword name in header",