diff options
Diffstat (limited to 'heap/hp_rnext.c')
| -rw-r--r-- | heap/hp_rnext.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/heap/hp_rnext.c b/heap/hp_rnext.c index 3b436fe87aa..4ecbe779107 100644 --- a/heap/hp_rnext.c +++ b/heap/hp_rnext.c @@ -33,11 +33,40 @@ int heap_rnext(HP_INFO *info, byte *record) heap_rb_param custom_arg; if (info->last_pos) + { + /* + We enter this branch for non-DELETE queries after heap_rkey() + or heap_rfirst(). As last key position (info->last_pos) is available, + we only need to climb the tree using tree_search_next(). + */ pos = tree_search_next(&keyinfo->rb_tree, &info->last_pos, offsetof(TREE_ELEMENT, left), offsetof(TREE_ELEMENT, right)); + } + else if (!info->lastkey_len) + { + /* + We enter this branch only for DELETE queries after heap_rfirst(). E.g. + DELETE FROM t1 WHERE a<10. As last key position is not available + (last key is removed by heap_delete()), we must restart search as it + is done in heap_rfirst(). + + It should be safe to handle this situation without this branch. That is + branch below should find smallest element in a tree as lastkey_len is + zero. tree_search_edge() is a kind of optimisation here as it should be + faster than tree_search_key(). + */ + pos= tree_search_edge(&keyinfo->rb_tree, info->parents, + &info->last_pos, offsetof(TREE_ELEMENT, left)); + } else { + /* + We enter this branch only for DELETE queries after heap_rkey(). E.g. + DELETE FROM t1 WHERE a=10. As last key position is not available + (last key is removed by heap_delete()), we must restart search as it + is done in heap_rkey(). + */ custom_arg.keyseg = keyinfo->seg; custom_arg.key_length = info->lastkey_len; custom_arg.search_flag = SEARCH_SAME | SEARCH_FIND; |