* Calculation of hint message when requested relation is not present in schema cache requires creation of a FuzzySet (to use fuzzy search to find candidate tables). For schemas with many tables it is costly.
This patch introduces dbTablesFuzzyIndex in SchemaCache to memoize the FuzzySet creation.
* Additionally, because of FuzzySet large memory requirements, this patch introduces a limit of 500 relations per schema, above which FuzzySet is not created and hint calculation disabled.
