diff options
Diffstat (limited to 'odb/nested-container.hxx')
| -rw-r--r-- | odb/nested-container.hxx | 179 |
1 files changed, 141 insertions, 38 deletions
diff --git a/odb/nested-container.hxx b/odb/nested-container.hxx index 67cf96f..d7e4ec1 100644 --- a/odb/nested-container.hxx +++ b/odb/nested-container.hxx @@ -1,5 +1,4 @@ // file : odb/nested-container.hxx -// copyright : Copyright (c) 2009-2019 Code Synthesis Tools CC // license : GNU GPL v2; see accompanying LICENSE file #ifndef ODB_NESTED_CONTAINER_HXX @@ -20,22 +19,29 @@ namespace odb { // Nested container emulation support for ODB. // - // Note that the outer key in the inner container should strictly - // speaking be a foreign key pointing to the key of the outer - // container. The only way to achieve this currently is to manually - // add the constraint via ALTER TABLE ADD CONSTRAINT. Note, however, - // that as long as we only modify these tables via the ODB container - // interface, not having the foreign key (and not having ON DELETE - // CASCADE) should be harmless (since we have a foreign key pointing - // to the object id). + // In a nutshell, the idea is to represent a nested container, for example, + // vector<vector<V>>, as map<nested_key, V> where nested_key is a composite + // key consisting of the outer and inner container indexes. // - - // Map key that is used to emulate nested container mapping in ODB. - // Template parameter T is a tag that allows us to distinguish keys - // for unrelated containers in order to assign column names, etc. - // Use inner container type for T. + // Note that with this approach the empty trailing entries of the outer + // container will not be added on load. It is assumed that the user handles + // that on their own, for example, by pre-loading the outer container entry + // members if there are any. + // + // Also note that the outer key in the inner container should strictly + // speaking be a foreign key pointing to the key of the outer container. The + // only way to achieve this currently is to manually add the constraint via + // ALTER TABLE ADD CONSTRAINT. Note, however, that as long as we only modify + // these tables via the ODB container interface, not having the foreign key + // (and not having ON DELETE CASCADE) should be harmless (since we have a + // foreign key pointing to the object id). + + // Map key that is used to emulate 1-level nested container mapping (for + // example, vector<vector<V>>). Template parameter IC is a tag that allows + // us to distinguish keys for unrelated containers in order to assign column + // names, etc. Use the inner container type (for example, vector<V>) for IC. // - template <typename T, + template <typename IC, typename O = std::size_t, typename I = std::size_t> struct nested_key @@ -55,10 +61,40 @@ namespace odb return outer < v.outer || (outer == v.outer && inner < v.inner); } }; + + // Map key that is used to emulate 2-level nested container mapping (for + // example, vector<vector<vector<V>>>>). Use the middle container type for + // MC (for example, vector<vector<V>>). + // + template <typename MC, + typename O = std::size_t, + typename M = std::size_t, + typename I = std::size_t> + struct nested2_key + { + using outer_type = O; + using middle_type = M; + using inner_type = I; + + outer_type outer; + middle_type middle; + inner_type inner; + + nested2_key () = default; + nested2_key (outer_type o, middle_type m, inner_type i) + : outer (o), middle (m), inner (i) {} + + bool + operator< (const nested2_key& v) const + { + return outer != v.outer ? outer < v.outer : + middle != v.middle ? middle < v.middle : + inner < v.inner ; + } + }; } #include <map> -#include <vector> #include <cstddef> // size_t #include <utility> // move(), declval() #include <cassert> @@ -66,46 +102,113 @@ namespace odb namespace odb { - // vector<vector<>> - // - template <typename IC> - struct nested_value_type: - std::remove_reference<decltype (std::declval<IC> ()[0])> {}; + template <typename C> + struct nested1_type: + std::remove_reference<decltype (std::declval<C> ()[0])> {}; + + template <typename C> + struct nested2_type: + std::remove_reference<decltype (std::declval<C> ()[0][0])> {}; + + template <typename C> + struct nested3_type: + std::remove_reference<decltype (std::declval<C> ()[0][0][0])> {}; - template <typename IC> - std::map<nested_key<IC>, typename nested_value_type<IC>::type> - nested_get (const std::vector<IC>& v) + // 1-level nesting. + // + template <typename OC> // For example, OC = vector<vector<V>>. + std::map<nested_key<typename nested1_type<OC>::type>, + typename nested2_type<OC>::type> + nested_get (const OC& oc) { using namespace std; - using I = typename nested_value_type<IC>::type; + using IC = typename nested1_type<OC>::type; + using V = typename nested2_type<OC>::type; using K = nested_key<IC>; - map<K, I> r; - for (size_t n (0); n != v.size (); ++n) + map<K, V> r; + for (size_t o (0); o != oc.size (); ++o) + { + const IC& ic (oc[o]); + for (size_t i (0); i != ic.size (); ++i) + r.emplace (K (o, i), ic[i]); + } + return r; + } + + template <typename K, typename V, typename OC> + void + nested_set (OC& oc, std::map<K, V>&& r) + { + using namespace std; + + for (auto& p: r) + { + size_t o (p.first.outer); + size_t i (p.first.inner); + V& v (p.second); + + if (o >= oc.size ()) + oc.resize (o + 1); + + assert (i == oc[o].size ()); + + oc[o].push_back (move (v)); + } + } + + // 2-level nesting. + // + template <typename OC> // For example, OC = vector<vector<vector<V>>>. + std::map<nested2_key<typename nested1_type<OC>::type>, + typename nested3_type<OC>::type> + nested2_get (const OC& oc) + { + using namespace std; + + using MC = typename nested1_type<OC>::type; + using V = typename nested3_type<OC>::type; + using K = nested2_key<MC>; + + map<K, V> r; + for (size_t o (0); o != oc.size (); ++o) { - const IC& o (v[n]); - for (size_t m (0); m != o.size (); ++m) - r.emplace (K (n, m), o[m]); + const auto& mc (oc[o]); + for (size_t m (0); m != mc.size (); ++m) + { + const auto& ic (mc[m]); + for (size_t i (0); i != ic.size (); ++i) + r.emplace (K (o, m, i), ic[i]); + } } return r; } - template <typename K, typename I, typename IC> + template <typename K, typename V, typename OC> void - nested_set (std::vector<IC>& v, std::map<K, I>&& r) + nested2_set (OC& oc, std::map<K, V>&& r) { using namespace std; for (auto& p: r) { - size_t n (p.first.outer); - size_t m (p.first.inner); - I& i (p.second); + size_t o (p.first.outer); + size_t m (p.first.middle); + size_t i (p.first.inner); + V& v (p.second); + + if (o >= oc.size ()) + oc.resize (o + 1); + + auto& mc (oc[o]); + + if (m >= mc.size ()) + mc.resize (m + 1); + + assert (i == mc[m].size ()); - assert (n < v.size ()); - assert (m == v[n].size ()); - v[n].push_back (move (i)); + mc[m].push_back (move (v)); } } } |