The average number of annual publications for CS postdocs
The main motive behind this question is to understand where am I standing with my own performance and productivity.

Then you're asking the wrong question.  The right metric to examine isn't the number of publication, but rather your visibility and reputation (and ultimately impact) within the research community.  If the intellectual leaders of your target subcommunity are eager to write you good recommendation letters, it doesn't matter whether you publish one paper a year or ten.  Similarly, if the intellectual leaders in your target subcommunity are not eager to write you good recommendation letters, it doesn't matter whether you publish one paper a year or ten.