Martchus
/
lmdb-safe
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Allow iterating over index 

The use-case is checking the index-value first (e.g. just a simple string)
to decide whether the object is actually instead of deserializing the
whole object (e.g. a huge object which is quite costly to deserialize)
directly.
This commit is contained in:
Martchus 2022-02-19 00:10:17 +01:00
parent 64ba75ac48
commit b87dd49bba
1 changed files with 27 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
lmdb-typed.hh
View File

@ -321,8 +321,8 @@ public:
// when on index, indirect
// we can be limited to one key, or iterate over entire database
// iter requires you to put the cursor in the right place first!
template <template <typename> class StorageType> struct iter_t {
using UsingDirectStorage = CppUtilities::Traits::IsSpecializationOf<StorageType<T>, DirectStorage>;
template <template <typename> class StorageType, typename ElementType = T> struct iter_t {
using UsingDirectStorage = CppUtilities::Traits::IsSpecializationOf<StorageType<ElementType>, DirectStorage>;
explicit iter_t(Parent *parent, typename Parent::cursor_t &&cursor, bool on_index, bool one_key, bool end = false)
: d_parent(parent)
@ -376,22 +376,22 @@ public:
return d_on_index ? d_data.get<string_view>() : d_id.get<string_view>();
}
StorageType<T> &allocatePointer()
StorageType<ElementType> &allocatePointer()
{
static_assert(!UsingDirectStorage::value, "Cannot call getPointer() when using direct storage.");
static_assert(
CppUtilities::Traits::IsSpecializingAnyOf<StorageType<T>, std::unique_ptr, std::shared_ptr>(), "Pointer type not supported.");
static_assert(CppUtilities::Traits::IsSpecializingAnyOf<StorageType<ElementType>, std::unique_ptr, std::shared_ptr>(),
"Pointer type not supported.");
if (d_t != nullptr) {
return d_t;
}
if constexpr (CppUtilities::Traits::IsSpecializationOf<StorageType<T>, std::unique_ptr>()) {
if constexpr (CppUtilities::Traits::IsSpecializationOf<StorageType<ElementType>, std::unique_ptr>()) {
return d_t = std::make_unique<T>();
} else if constexpr (CppUtilities::Traits::IsSpecializationOf<StorageType<T>, std::shared_ptr>()) {
} else if constexpr (CppUtilities::Traits::IsSpecializationOf<StorageType<ElementType>, std::shared_ptr>()) {
return d_t = std::make_shared<T>();
}
}
StorageType<T> &getPointer()
StorageType<ElementType> &getPointer()
{
static_assert(!UsingDirectStorage::value, "Cannot call getPointer() when using direct storage.");
if (!d_deserialized) {
@ -402,7 +402,7 @@ public:
return d_t;
}
T &derefValue()
ElementType &derefValue()
{
if constexpr (UsingDirectStorage::value) {
return d_t;
@ -412,7 +412,7 @@ public:
}
}
T &value()
ElementType &value()
{
auto &res = derefValue();
if (!d_deserialized) {
@ -422,12 +422,12 @@ public:
return res;
}
const T &operator*()
const ElementType &operator*()
{
return value();
}
const T *operator->()
const ElementType *operator->()
{
return &value();
}
@ -485,7 +485,7 @@ public:
bool d_one_key;
bool d_end;
bool d_deserialized;
CppUtilities::Traits::Conditional<UsingDirectStorage, T, StorageType<T>> d_t;
CppUtilities::Traits::Conditional<UsingDirectStorage, ElementType, StorageType<ElementType>> d_t;
};
template <std::size_t N, template <typename> class StorageType = DirectStorage> iter_t<StorageType> genbegin(MDB_cursor_op op)
@ -526,6 +526,20 @@ public:
return iter_t<StorageType>{ &d_parent, std::move(cursor), false, false };
};
template <std::size_t N, template <typename> class StorageType = DirectStorage> iter_t<DirectStorage, std::uint32_t> begin_idx()
{
typename Parent::cursor_t cursor = (*d_parent.d_txn)->getCursor(std::get<N>(d_parent.d_parent->d_tuple).d_idx);
MDBOutVal out, id;
if (cursor.get(out, id, MDB_FIRST)) {
// on_index, one_key, end
return iter_t<DirectStorage, std::uint32_t>{ &d_parent, std::move(cursor), false, false, true };
}
return iter_t<DirectStorage, std::uint32_t>{ &d_parent, std::move(cursor), false, false };
}
eiter_t end()
{
return eiter_t();