What province is the pure and ambiguous Songjiang city?

This is a fictional city, but it is basically certain that the prototype is in the northeast, because the protagonist's family calls themselves Northeasters. Judging from the year when this novel was written, there will be snow, sea and subway. Songjiang should be based on Dalian, and the prototype of the East China Sea is generally Shenyang.

Of course, there is a place name Songjiang, and there is a Songjiang District in Shanghai, but it is too far from the plot written in the novel to be ruled out directly.