mutation_reader_test: add unit test for evictable reader range tombstone trimming

test/boost/mutation_reader_test.cc

@@ -2984,3 +2984,148 @@ SEASTAR_THREAD_TEST_CASE(test_manual_paused_evictable_reader_is_mutation_source)
 
     run_mutation_source_tests(make_populate);
 }
+
+namespace {
+
+std::deque<mutation_fragment> copy_fragments(const schema& s, const std::deque<mutation_fragment>& o) {
+    std::deque<mutation_fragment> buf;
+    for (const auto& mf : o) {
+        buf.emplace_back(s, mf);
+    }
+    return buf;
+}
+
+flat_mutation_reader create_evictable_reader_and_evict_after_first_buffer(
+        schema_ptr schema,
+        reader_permit permit,
+        const dht::partition_range& prange,
+        const query::partition_slice& slice,
+        std::deque<mutation_fragment> first_buffer,
+        position_in_partition_view last_fragment_position,
+        std::deque<mutation_fragment> second_buffer,
+        size_t max_buffer_size) {
+    class factory {
+        schema_ptr _schema;
+        std::optional<std::deque<mutation_fragment>> _first_buffer;
+        std::optional<std::deque<mutation_fragment>> _second_buffer;
+        size_t _max_buffer_size;
+
+    private:
+        std::optional<std::deque<mutation_fragment>> copy_buffer(const std::optional<std::deque<mutation_fragment>>& o) {
+            if (!o) {
+                return {};
+            }
+            return copy_fragments(*_schema, *o);
+        }
+
+    public:
+        factory(schema_ptr schema, std::deque<mutation_fragment> first_buffer, std::deque<mutation_fragment> second_buffer, size_t max_buffer_size)
+            : _schema(std::move(schema)), _first_buffer(std::move(first_buffer)), _second_buffer(std::move(second_buffer)), _max_buffer_size(max_buffer_size) {
+        }
+
+        factory(const factory& o)
+            : _schema(o._schema)
+            , _first_buffer(copy_buffer(o._first_buffer))
+            , _second_buffer(copy_buffer(o._second_buffer)) {
+        }
+        factory(factory&& o) = default;
+
+        flat_mutation_reader operator()(
+                schema_ptr s,
+                reader_permit permit,
+                const dht::partition_range& range,
+                const query::partition_slice& slice,
+                const io_priority_class& pc,
+                tracing::trace_state_ptr trace_state,
+                streamed_mutation::forwarding fwd_sm,
+                mutation_reader::forwarding fwd_mr) {
+            BOOST_REQUIRE(s == _schema);
+            if (_first_buffer) {
+                auto buf = *std::exchange(_first_buffer, {});
+                auto rd = make_flat_mutation_reader_from_fragments(_schema, std::move(buf));
+                rd.set_max_buffer_size(_max_buffer_size);
+                return rd;
+            }
+            if (_second_buffer) {
+                auto buf = *std::exchange(_second_buffer, {});
+                auto rd = make_flat_mutation_reader_from_fragments(_schema, std::move(buf));
+                rd.set_max_buffer_size(_max_buffer_size);
+                return rd;
+            }
+            return make_empty_flat_reader(_schema);
+        }
+    };
+    auto ms = mutation_source(factory(schema, std::move(first_buffer), std::move(second_buffer), max_buffer_size));
+
+    auto [rd, handle] = make_manually_paused_evictable_reader(
+            std::move(ms),
+            schema,
+            permit,
+            prange,
+            slice,
+            seastar::default_priority_class(),
+            nullptr,
+            mutation_reader::forwarding::yes);
+
+    rd.set_max_buffer_size(max_buffer_size);
+
+    rd.fill_buffer(db::no_timeout).get0();
+
+    const auto eq_cmp = position_in_partition::equal_compare(*schema);
+    BOOST_REQUIRE(rd.is_buffer_full());
+    BOOST_REQUIRE(eq_cmp(rd.buffer().back().position(), last_fragment_position));
+    BOOST_REQUIRE(!rd.is_end_of_stream());
+
+    rd.detach_buffer();
+
+    handle.pause();
+
+    while(permit.semaphore().try_evict_one_inactive_read());
+
+    return std::move(rd);
+}
+
+}
+
+SEASTAR_THREAD_TEST_CASE(test_evictable_reader_trim_range_tombstones) {
+    reader_concurrency_semaphore semaphore(reader_concurrency_semaphore::no_limits{}, get_name());
+    simple_schema s;
+
+    const auto pkey = s.make_pkey();
+    size_t max_buffer_size = 512;
+    const int first_ck = 100;
+    const int second_buffer_ck = first_ck + 100;
+
+    size_t mem_usage = 0;
+
+    std::deque<mutation_fragment> first_buffer;
+    first_buffer.emplace_back(partition_start{pkey, {}});
+    mem_usage = first_buffer.back().memory_usage(*s.schema());
+    for (int i = 0; i < second_buffer_ck; ++i) {
+        first_buffer.emplace_back(s.make_row(s.make_ckey(i++), "v"));
+        mem_usage += first_buffer.back().memory_usage(*s.schema());
+    }
+    const auto last_fragment_position = position_in_partition(first_buffer.back().position());
+    max_buffer_size = mem_usage;
+    first_buffer.emplace_back(s.make_row(s.make_ckey(second_buffer_ck), "v"));
+
+    std::deque<mutation_fragment> second_buffer;
+    second_buffer.emplace_back(partition_start{pkey, {}});
+    mem_usage = second_buffer.back().memory_usage(*s.schema());
+    second_buffer.emplace_back(s.make_range_tombstone(query::clustering_range::make_ending_with(s.make_ckey(second_buffer_ck + 10))));
+    int ckey = second_buffer_ck;
+    while (mem_usage <= max_buffer_size) {
+        second_buffer.emplace_back(s.make_row(s.make_ckey(ckey++), "v"));
+        mem_usage += second_buffer.back().memory_usage(*s.schema());
+    }
+    second_buffer.emplace_back(partition_end{});
+
+    auto rd = create_evictable_reader_and_evict_after_first_buffer(s.schema(), semaphore.make_permit(), query::full_partition_range,
+            s.schema()->full_slice(), std::move(first_buffer), last_fragment_position, std::move(second_buffer), max_buffer_size);
+
+    rd.fill_buffer(db::no_timeout).get();
+
+    const auto tri_cmp = position_in_partition::tri_compare(*s.schema());
+
+    BOOST_REQUIRE(tri_cmp(last_fragment_position, rd.peek_buffer().position()) < 0);
+}