Merge pull request #454 from oscar-system/bl/dblength

src/polydb.jl

@@ -85,6 +85,45 @@ Polymake.Polydb.Collection{Polymake.BigObject}: Matroids.Small
 """
 Base.getindex(db::Database, name::AbstractString) = Collection{Polymake.BigObject}(db.mdb[name])
 
+"""
+      length(c::Collection{T}, d::Dict=Dict())
+
+Count documents in a collection `c` matching the criteria given by `d`.
+
+# Examples
+```julia-repl
+julia> db = Polymake.Polydb.get_db();
+
+julia> collection = db["Polytopes.Lattice.SmoothReflexive"];
+
+julia> query = Dict("DIM"=>3, "N_FACETS"=>5);
+
+julia> length(collection, query)
+4
+```
+"""
+function Base.length(c::Collection{T}, d::Dict=Dict()) where T
+   return Base.length(c.mcol, Mongoc.BSON(d))
+end
+
+"""
+      length(c::Collection{T}, d::Pair...)
+
+Count documents in a collection `c` matching the criteria given by `d`.
+
+# Examples
+```julia-repl
+julia> db = Polymake.Polydb.get_db();
+
+julia> collection = db["Polytopes.Lattice.SmoothReflexive"];
+
+julia> length(collection, "DIM"=>3, "N_FACETS"=>5)
+4
+```
+"""
+function Base.length(c::Collection{T}, d::Pair...) where T
+   return Base.length(c.mcol, Mongoc.BSON(d...))
+end
 """
       find(c::Collection{T}, d::Dict=Dict(); opts::Union{Nothing, Dict})
 

test/polydb.jl

@@ -45,6 +45,12 @@ using Polymake.Polydb.Mongoc
         results_bson = Polymake.Polydb.find(collection_bson, constraints...)
         @test Polymake.Polydb.Cursor{Polymake.BigObject}(results_bson) isa Polymake.Polydb.Cursor
         @test Polymake.Polydb.Cursor{Polymake.BigObject}(results_bson) isa Polymake.Polydb.Cursor{Polymake.BigObject}
+
+        @test length(collection_bo, constraints...) == 7
+        @test length(collection_bo, query) == 7
+        @test length(collection_bson, constraints...) == 7
+        @test length(collection_bson, query) == 7
+
         @testset verbose=true "Iterator (Cursor)" begin
             @test iterate(results_bo) isa Tuple{Polymake.BigObject, Nothing}
             @test iterate(results_bson) isa Tuple{Mongoc.BSON, Nothing}