算法2：连接优化

1: Σ'←∅

2: for all σ∈Σ do

3: let $\sigma =\phi \left(\overline{X}\right)\to \exists \overline{Y},\psi \left(\overline{X},\overline{Y}\right)$

4: Σ_t←{σ}

5: for all $x\in \overline{X}$ do

6: if variable x occurs more than once in φ then

7: Cexplored ←Σ_t

8: Σ_t←∅

9: Σ_t←Σ_t∪VarJoinsRefinement(Cexplored, x)

10: end if

11: end for

12: Σ'←Σ'∪Σ_t

13:Σ_t←∅

14: end for

15: return Σ'