Add simple test for aggregates.

Also put a little TODO reminder.

Author: Sean1708

src/UDF.jl

@@ -120,6 +120,8 @@ function finalfunc(init, func, fsym=symbol(string(func)*"_final"))
     nm = isdefined(Base,fsym) ? :(Base.$fsym) : fsym
     return quote
         function $(nm)(context::Ptr{Void}, nargs::Cint, values::Ptr{Ptr{Void}})
+            # TODO: I don't think arguments are ever passed to this function,
+            # should we leave them in anyway?
             args = [sqlvalue(context, i) for i in 1:nargs]
             acptr = sqlite3_aggregate_context(context, 0)
             # step function wasn't run

test/runtests.jl

@@ -207,6 +207,12 @@ SQLite.@register db big
 r = query(db, "SELECT big(5)")
 @test r[1][1] == big(5)
 
+doublesum_step(persist, current) = persist + current
+doublesum_final(persist) = 2 * persist
+register(db, 0, doublesum_step, doublesum_final, name="doublesum")
+r = query(db, "SELECT doublesum(UnitPrice) FROM Track")
+s = query(db, "SELECT UnitPrice FROM Track")
+@test_approx_eq r[1][1] 2*sum(s[1])
 
 db2 = SQLiteDB()
 query(db2, "CREATE TABLE tab1 (r REAL, s INT)")