upgrade.md

title	layout
Upgrading Your Project to Cascalog 2.0	article

Purpose

Cascalog 2.0 is a major improvement over 1.x. The underlying query parser remains the same but there are several notable breaking API changes. This is a guide to point out the major differences between 2.x and 1.x versions of Cascalog to help you make the upgrade.

Breaking API changes at a glance

• Most namespaces have been moved into either cascalog.cascading.* or cascalog.logic.*
  • cascalog.ops → cascalog.logic.ops
  • cascalog.vars → cascalog.logic.vars
• Higher-order functions using extra vector around a function name, like (defmapop [times [x]] [y] (* x y)) is no longer supported in favour of using anonymous functions
• Built-in ops use anonymous functions to set pameters. For example, (c/limit [1] ...) is now ((c/limit 1) ...)
• Functions can be passed directly instead of as vars. For example,

(def src [1 2 3 4 5]) 
(defn square [x] (* x x))
(defn my-query [op]
  (??<- [!x !y]
        (src !x)
        (op !x :> !y)))

(my-query #'square)

now becomes

(my-query square)

Non-breaking changes

Cascalog operations are now just functions, so the def*op names have been deprecated in favor of names that sound like functions, def*fn. A few examples:

• deffilterop → deffilterfn
• defbufferop → defbufferfn
• defmapop → defmapfn