dsdb/linked_attributes: shortcut exit for backlink fix

In most cases there can only be one link for each GUID. If we assume
that is true, we can skip half the search, on average.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/source4/dsdb/samdb/ldb_modules/linked_attributes.c b/source4/dsdb/samdb/ldb_modules/linked_attributes.c
index 0ef15a18aa3aad5d2375f8b65db26955aa04588e..81bb31b714c8058119464e559956dec398270cfa 100644 (file)
--- a/source4/dsdb/samdb/ldb_modules/linked_attributes.c
+++ b/source4/dsdb/samdb/ldb_modules/linked_attributes.c
@@ -700,13 +700,15 @@ static int linked_attributes_fix_link_slow(struct ldb_module *module,
                                           struct ldb_message *msg,
                                           struct ldb_dn *new_dn,
                                           struct GUID self_guid,
-                                          const char *syntax_oid)
+                                          const char *syntax_oid,
+                                          const char *reverse_syntax_oid)
 {
        int ret;
        unsigned int i;
        struct GUID link_guid;
        struct ldb_message_element *el = &msg->elements[0];
        struct ldb_context *ldb = ldb_module_get_ctx(module);
+       bool has_unique_value = strcmp(reverse_syntax_oid, LDB_SYNTAX_DN) == 0;
        TALLOC_CTX *tmp_ctx = talloc_new(module);
        if (tmp_ctx == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
@@ -720,7 +722,12 @@ static int linked_attributes_fix_link_slow(struct ldb_module *module,
         * DN+Binary link.
         *
         * This is used for unsorted links, which is to say back links and
-        * forward links on old databases.
+        * forward links on old databases. It necessarily involves a linear
+        * search, though when the link is a plain DN link, we can skip
+        * checking as soon as we find it.
+        *
+        * NOTE: if there are duplicate links, the extra ones will end up as
+        * dangling links to the old DN. This may or may not be better.
         */
        for (i = 0; i < el->num_values; i++) {
                struct dsdb_dn *dsdb_dn = dsdb_dn_parse(msg,
@@ -758,6 +765,9 @@ static int linked_attributes_fix_link_slow(struct ldb_module *module,
 
                el->values[i] = data_blob_string_const(
                        dsdb_dn_get_extended_linearized(el->values, dsdb_dn, 1));
+               if (has_unique_value) {
+                       break;
+               }
        }
 
        talloc_free(tmp_ctx);
@@ -1075,7 +1085,8 @@ static int linked_attributes_fix_links(struct ldb_module *module,
                                msg,
                                new_dn,
                                self_guid,
-                               target->syntax->ldap_oid);
+                               target->syntax->ldap_oid,
+                               schema_attr->syntax->ldap_oid);
                } else {
                        /* we can binary search to find forward links */
                        ret = linked_attributes_fix_forward_link(