Avoid extra copies of functions in copy_to

Author: blegat

src/Utilities/copy.jl

@@ -40,6 +40,20 @@ function pass_attributes(dest::MOI.ModelLike, src::MOI.ModelLike, index_map)
     return
 end
 
+function _pass_attribute(
+    dest::MOI.ModelLike,
+    src::MOI.ModelLike,
+    index_map,
+    ::MOI.ConstraintFunction{F},
+) where {F}
+    return _pass_attribute(
+        dest,
+        src,
+        index_map,
+        UnsafeConstraintFunction{F}(),
+    )
+end
+
 function _pass_attribute(
     dest::MOI.ModelLike,
     src::MOI.ModelLike,
@@ -175,7 +189,10 @@ function _copy_constraints(
     cis_src::Vector{<:MOI.ConstraintIndex},
 )
     for ci in cis_src
-        f = MOI.get(src, MOI.ConstraintFunction(), ci)
+        # MOI does not allows the implementation of `MOI.constraint`
+        # to modify it or hold a copy of it.
+        # `map_indices` is also often going to copy it anyway
+        f = MOI.get(src, UnsafeConstraintFunction(), ci)
         s = MOI.get(src, MOI.ConstraintSet(), ci)
         index_map_FS[ci] =
             MOI.add_constraint(dest, map_indices(index_map, f), s)

src/Utilities/model.jl

@@ -402,7 +402,7 @@ end
 
 function MOI.get(
     model::AbstractModel,
-    attr::Union{MOI.ConstraintFunction,MOI.ConstraintSet},
+    attr::Union{UnsafeConstraintFunction,MOI.ConstraintFunction,MOI.ConstraintSet},
     ci::MOI.ConstraintIndex,
 )
     return MOI.get(constraints(model, ci), attr, ci)
@@ -530,7 +530,7 @@ function MOI.supports(model::AbstractModel, attr::MOI.ObjectiveFunction)
     return MOI.supports(model.objective, attr)
 end
 
-function MOI.get(model::AbstractModel, attr::MOI.ObjectiveFunction)
+function MOI.get(model::AbstractModel, attr::Union{UnsafeObjectiveFunction,MOI.ObjectiveFunction})
     return MOI.get(model.objective, attr)
 end
 

src/Utilities/objective_container.jl

@@ -116,6 +116,12 @@ function MOI.supports(
     return true
 end
 
+struct UnsafeObjectiveFunction{F<:MOI.AbstractFunction} end
+
+function MOI.get(model::MOI.ModelLike, ::UnsafeObjectiveFunction{F}) where {F}
+    return MOI.get(model, MOI.ObjectiveFunction{F}())
+end
+
 function MOI.get(
     o::ObjectiveContainer{T},
     attr::MOI.ObjectiveFunction{F},
@@ -153,6 +159,10 @@ function MOI.get(
     return convert(F, zero(MOI.ScalarAffineFunction{T}))
 end
 
+function MOI.get(o::ObjectiveContainer, ::MOI.ObjectiveFunction{F}) where {F}
+    return copy(MOI.get(o, UnsafeObjectiveFunction{F}()))
+end
+
 function _empty_keeping_sense(o::ObjectiveContainer)
     sense, is_sense_set = o.sense, o.is_sense_set
     MOI.empty!(o)

src/Utilities/vector_of_constraints.jl

@@ -96,14 +96,28 @@ function MOI.delete(
     return
 end
 
+struct UnsafeConstraintFunction end
+
+function MOI.get(model::MOI.ModelLike, ::UnsafeConstraintFunction, ci::MOI.ConstraintIndex)
+    return MOI.get(model, MOI.ConstraintFunction, ci)
+end
+
 function MOI.get(
     v::VectorOfConstraints{F,S},
-    ::MOI.ConstraintFunction,
+    ::UnsafeConstraintFunction,
     ci::MOI.ConstraintIndex{F,S},
 ) where {F,S}
     MOI.throw_if_not_valid(v, ci)
     f, _ = v.constraints[ci]::Tuple{F,S}
-    return copy(f)
+    return f
+end
+
+function MOI.get(
+    v::VectorOfConstraints{F,S},
+    ::MOI.ConstraintFunction,
+    ci::MOI.ConstraintIndex{F,S},
+) where {F,S}
+    return copy(MOI.get(v, MOI.UnsafeConstraintFunction, ci))
 end
 
 function MOI.get(