Quantity vs Quality of Publication during PhD
I don't know what publication rates are typical in computer science, but in mathematics it is true that quality is more important than quantity, when it comes to getting postdocs and competitive research positions. 

This does not mean quantity is irrelevant. But postdocs are partially given based on your promise as a researcher. To that end, one truly excellent paper may be enough to land a job (along with good references), because it suggests you have the potential to produce more excellent papers. On the other hand, 10 truly mediocre papers is not likely to be as impressive, because it only shows you can publish lots of mediocre papers.