In build 1729, we introduced a breaking change for those that override the BuildSearchIndex method in one or more content classes.
The method signature has changed in this new version. Previously it was:
public virtual void BuildSearchIndex(StringBuilder index, int lcid, bool protectedContent, int recurseLevelLimit, ref int recurseCountLimit)
In builds newer than 1729 it is:
public virtual void BuildSearchIndex(StringBuilder index, int lcid, bool protectedContent, bool allowRecursion)
The improvement that introduced this change will make indexing more stable and less memory hungry. It is also a lot easier to get related content indexed. See this new description for more details.