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partition_snapshot_row_cursor: Relax vector of iterators

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The cursor maintains a vector of iterators that correspond to
each of the versions scanned. However, only the iterator in
the latest one is really needed, so the whole vector can be
reduced down to an optional.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This commit is contained in:
Pavel Emelyanov
2021-04-07 11:06:20 +03:00
parent 26e27e27e8
commit 2fb0f7315c
1 changed files with 21 additions and 17 deletions
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38
partition_snapshot_row_cursor.hh
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@@ -128,8 +128,8 @@ class partition_snapshot_row_cursor final {
const schema& _schema;
partition_snapshot& _snp;
utils::small_vector<position_in_version, 2> _heap;
utils::small_vector<mutation_partition::rows_type::iterator, 2> _iterators;
utils::small_vector<position_in_version, 2> _current_row;
std::optional<mutation_partition::rows_type::iterator> _latest_it;
bool _continuous{};
bool _dummy{};
const bool _unique_owner;
@@ -166,7 +166,7 @@ class partition_snapshot_row_cursor final {
position_in_version::less_compare heap_less(_schema);
_heap.clear();
_current_row.clear();
_iterators.clear();
_latest_it.reset();
int version_no = 0;
bool unique_owner = _unique_owner;
bool first = true;
@@ -175,7 +175,9 @@ class partition_snapshot_row_cursor final {
auto& rows = v.partition().clustered_rows();
auto pos = rows.lower_bound(lower_bound, cmp);
auto end = rows.end();
_iterators.push_back(pos);
if (first) {
_latest_it = pos;
}
if (pos != end) {
_heap.push_back({pos, end, version_no, unique_owner});
}
@@ -193,7 +195,8 @@ public:
{ }
mutation_partition::rows_type::iterator get_iterator_in_latest_version() const {
return _iterators[0];
assert(_latest_it);
return *_latest_it;
}
// Returns true iff the iterators obtained since the cursor was last made valid
@@ -242,7 +245,8 @@ public:
position_in_partition::equal_compare eq(_schema);
position_in_version::less_compare heap_less(_schema);
auto& rows = _snp.version()->partition().clustered_rows();
auto it = _iterators[0] = rows.lower_bound(_position, cmp);
auto it = rows.lower_bound(_position, cmp);
_latest_it = it;
auto heap_i = boost::find_if(_heap, [](auto&& v) { return v.version_no == 0; });
if (it == rows.end()) {
if (heap_i != _heap.end()) {
@@ -308,7 +312,9 @@ public:
assert(iterators_valid());
for (auto&& curr : _current_row) {
++curr.it;
_iterators[curr.version_no] = curr.it;
if (curr.version_no == 0) {
_latest_it = curr.it;
}
if (curr.it != curr.end) {
_heap.push_back(curr);
boost::range::push_heap(_heap, heap_less);
@@ -336,7 +342,9 @@ public:
} else {
++curr.it;
}
_iterators[curr.version_no] = curr.it;
if (curr.version_no == 0) {
_latest_it = curr.it;
}
if (curr.it != curr.end) {
_heap.push_back(curr);
boost::range::push_heap(_heap, heap_less);
@@ -514,20 +522,16 @@ public:
first = false;
out << "{v=" << v.version_no << ", pos=" << v.it->position() << ", cont=" << v.it->continuous() << "}";
}
out << "], iterators=[\n ";
first = true;
auto v = cur._snp.versions().begin();
for (auto&& i : cur._iterators) {
if (!first) {
out << ",\n ";
}
first = false;
if (i == v->partition().clustered_rows().end()) {
out << "], latest_iterator=[";
if (cur._latest_it) {
mutation_partition::rows_type::iterator i = *cur._latest_it;
if (!i) {
out << "end";
} else {
out << i->position();
}
++v;
} else {
out << "<none>";
}
return out << "]}";
};