regarding data structure used for linker symbol table

[Dharmendra]

normally  hash table with buckets is used for storing the global symbol
info in the memory for a linker.as the number of global symbols is not
known before hand ,the hashing function and the table size is hard to be
decided.
        so why don't we use hash tabled trees (i.e. binary tree in the
place of buckets ).on the average buckets have time complexity of O(n) for
search and O(1) for insertion  which sums up to O(n).
        in the hash tabled tree the insertion will take O(ln n) and the
search will take O(ln n) (because the  variable names are random so the
probability of the tree of becoming a linked list is very low) which  sums
up to O(ln n) which could provide very big advantage over the bucket
design.
        could you please clear whether there is some flaw in my design
?
                                thanx 
                                  Dharmender Rai