Learnability of constraint satisfaction problems CSPs?
You are probably looking for this paper:


Víctor Dalmau and Peter Jeavons, Learnability of quantified formulas, TCS 306 485–511, 2003.  doi:10.1016/S0304-3975(03)00342-6


In short, the learning complexity of a family of quantified formulas over a finite domain of values is determined by its clone of polymorphisms.  This includes CSPs as a special case of more general quantified formulas (since a CSP instance is just an existentially quantified conjunctive formula).

For the Boolean case and also for two broad classes of non-Boolean formulas, there is a dichotomy between polynomially learnable (via the Generating Set algorithm, if the clone contains a "nice" operation) and not, subject to the hypothesis that there exists a public key cryptosystem secure against chosen ciphertext attacks.