deletions | additions       diff --git a/section_Query_Optimization_and_Execution__.tex b/section_Query_Optimization_and_Execution__.tex  index 5262b2a..90667e0 100644  --- a/section_Query_Optimization_and_Execution__.tex  +++ b/section_Query_Optimization_and_Execution__.tex 
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$$ S(N) = 1 if $N \ = \ 1$ $$   \\   $$ S(N) $S(N)  = \displaystyle \sum_{N=1}^{i} (N)(N-i) (N)(N-i)$  \ $ if N > 1$ $$\\ Therefore the number of possible permutations are $S(N)*N!$. Unlike left-deep tree case, estimating the cost for all the possible bushy trees is computationally infeasible for moderately large N (~7). Therefore it is required to come with a heuristic to select set of permutations for cost computations.  \subsection{Heuristics to Select Bushy Trees}