diff options
| -rw-r--r-- | source3/registry/reg_backend_db.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/source3/registry/reg_backend_db.c b/source3/registry/reg_backend_db.c index f6471d04ee..344bc4124d 100644 --- a/source3/registry/reg_backend_db.c +++ b/source3/registry/reg_backend_db.c @@ -881,6 +881,29 @@ done: return ret; } +/* + * regdb_key_exists() is a very frequent operation. It can be quite + * time-consuming to fully fetch the parent's subkey list, talloc_strdup all + * subkeys and then compare the keyname linearly to all the parent's subkeys. + * + * The following code tries to make this operation as efficient as possible: + * Per registry key we create a list of subkeys that is very efficient to + * search for existence of a subkey. Its format is: + * + * 4 bytes num_subkeys + * 4*num_subkey bytes offset into the string array + * then follows a sorted list of subkeys in uppercase + * + * This record is created by create_sorted_subkeys() on demand if it does not + * exist. scan_parent_subkeys() uses regdb->parse_record to search the sorted + * list, the parsing code and the binary search can be found in + * parent_subkey_scanner. The code uses parse_record() to avoid a memcpy of + * the potentially large subkey record. + * + * The sorted subkey record is deleted in regdb_store_keys_internal and + * recreated on demand. + */ + static int cmp_keynames(const void *p1, const void *p2) { return StrCaseCmp(*((char **)p1), *((char **)p2)); |