Rename first used generation -> oldest used generation.

30 files changed, 111 insertions, 113 deletions

diff --git a/searchcore/src/tests/proton/attribute/imported_attributes_context/imported_attributes_context_test.cpp b/searchcore/src/tests/proton/attribute/imported_attributes_context/imported_attributes_context_test.cpp
index c52978261a7..7a5c76b201a 100644
--- a/searchcore/src/tests/proton/attribute/imported_attributes_context/imported_attributes_context_test.cpp
+++ b/searchcore/src/tests/proton/attribute/imported_attributes_context/imported_attributes_context_test.cpp
@@ -56,10 +56,11 @@ hasActiveEnumGuards(AttributeVector &attr)
 }
 
 void
-assertGuards(AttributeVector &attr, generation_t expCurrentGeneration, generation_t expFirstUsedGeneration, bool expHasActiveEnumGuards)
+assertGuards(AttributeVector &attr, generation_t expCurrentGeneration, generation_t exp_oldest_used_generation,
+             bool expHasActiveEnumGuards)
 {
     EXPECT_EQUAL(expCurrentGeneration, attr.getCurrentGeneration());
-    EXPECT_EQUAL(expFirstUsedGeneration, attr.getFirstUsedGeneration());
+    EXPECT_EQUAL(exp_oldest_used_generation, attr.get_oldest_used_generation());
     EXPECT_EQUAL(expHasActiveEnumGuards, hasActiveEnumGuards(attr));
 }
 
diff --git a/searchcore/src/tests/proton/reference/gid_to_lid_mapper/gid_to_lid_mapper_test.cpp b/searchcore/src/tests/proton/reference/gid_to_lid_mapper/gid_to_lid_mapper_test.cpp
index 2f4c26094c7..5152d09fae5 100644
--- a/searchcore/src/tests/proton/reference/gid_to_lid_mapper/gid_to_lid_mapper_test.cpp
+++ b/searchcore/src/tests/proton/reference/gid_to_lid_mapper/gid_to_lid_mapper_test.cpp
@@ -126,11 +126,11 @@ struct Fixture
         return std::make_shared<GidToLidMapperFactory>(_dmsContext);
     }
 
-    void assertGenerations(generation_t currentGeneration, generation_t firstUsedGeneration)
+    void assertGenerations(generation_t currentGeneration, generation_t oldest_used_generation)
     {
         const GenerationHandler &handler = _dms->getGenerationHandler();
         EXPECT_EQUAL(currentGeneration, handler.getCurrentGeneration());
-        EXPECT_EQUAL(firstUsedGeneration, handler.getFirstUsedGeneration());
+        EXPECT_EQUAL(oldest_used_generation, handler.get_oldest_used_generation());
     }
 
     template <typename Function>
diff --git a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
index eeb8cafb859..c153f873480 100644
--- a/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
+++ b/searchcore/src/vespa/searchcore/proton/attribute/attribute_vector_explorer.cpp
@@ -47,7 +47,7 @@ convertStatusToSlime(const Status &status, Cursor &object)
 void
 convertGenerationToSlime(const AttributeVector &attr, Cursor &object)
 {
-    object.setLong("firstUsed", attr.getFirstUsedGeneration());
+    object.setLong("oldest_used", attr.get_oldest_used_generation());
     object.setLong("current", attr.getCurrentGeneration());
 }
 
diff --git a/searchlib/src/tests/attribute/attributemanager/attributemanager_test.cpp b/searchlib/src/tests/attribute/attributemanager/attributemanager_test.cpp
index 7f0a88c9f86..3fa74b78d2a 100644
--- a/searchlib/src/tests/attribute/attributemanager/attributemanager_test.cpp
+++ b/searchlib/src/tests/attribute/attributemanager/attributemanager_test.cpp
@@ -38,8 +38,7 @@ public:
     generation_t getGen() const { return getCurrentGeneration(); }
     uint32_t getRefCount(generation_t gen) const { return getGenerationRefCount(gen); }
     void incGen() { incGeneration(); }
-    void updateFirstUsedGen() { updateFirstUsedGeneration(); }
-    generation_t getFirstUsedGen() const { return getFirstUsedGeneration(); }
+    generation_t oldest_used_gen() const { return get_oldest_used_generation(); }
 };
 
 
@@ -49,35 +48,35 @@ TEST("Test attribute guards")
     TestAttribute * v = static_cast<TestAttribute *> (vec.get());
     EXPECT_EQUAL(v->getGen(), unsigned(0));
     EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
-    EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(0));
+    EXPECT_EQUAL(v->oldest_used_gen(), unsigned(0));
     {
         AttributeGuard g0(vec);
         EXPECT_EQUAL(v->getGen(), unsigned(0));
         EXPECT_EQUAL(v->getRefCount(0), unsigned(1));
-        EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(0));
+        EXPECT_EQUAL(v->oldest_used_gen(), unsigned(0));
         {
             AttributeGuard g1(vec);
             EXPECT_EQUAL(v->getGen(), unsigned(0));
             EXPECT_EQUAL(v->getRefCount(0), unsigned(2));
-            EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(0));
+            EXPECT_EQUAL(v->oldest_used_gen(), unsigned(0));
         }
         EXPECT_EQUAL(v->getRefCount(0), unsigned(1));
-        EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(0));
+        EXPECT_EQUAL(v->oldest_used_gen(), unsigned(0));
     }
     EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
-    EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(0));
+    EXPECT_EQUAL(v->oldest_used_gen(), unsigned(0));
 
     v->incGen();
     EXPECT_EQUAL(v->getGen(), unsigned(1));
     EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
     EXPECT_EQUAL(v->getRefCount(1), unsigned(0));
-    EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(1));
+    EXPECT_EQUAL(v->oldest_used_gen(), unsigned(1));
     {
         AttributeGuard g0(vec);
         EXPECT_EQUAL(v->getGen(), unsigned(1));
         EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
         EXPECT_EQUAL(v->getRefCount(1), unsigned(1));
-        EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(1));
+        EXPECT_EQUAL(v->oldest_used_gen(), unsigned(1));
         {
             v->incGen();
             AttributeGuard g1(vec);
@@ -85,19 +84,19 @@ TEST("Test attribute guards")
             EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
             EXPECT_EQUAL(v->getRefCount(1), unsigned(1));
             EXPECT_EQUAL(v->getRefCount(2), unsigned(1));
-            EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(1));
+            EXPECT_EQUAL(v->oldest_used_gen(), unsigned(1));
         }
         EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
         EXPECT_EQUAL(v->getRefCount(1), unsigned(1));
         EXPECT_EQUAL(v->getRefCount(2), unsigned(0));
-        EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(1));
+        EXPECT_EQUAL(v->oldest_used_gen(), unsigned(1));
     }
     EXPECT_EQUAL(v->getRefCount(0), unsigned(0));
     EXPECT_EQUAL(v->getRefCount(1), unsigned(0));
     EXPECT_EQUAL(v->getRefCount(2), unsigned(0));
-    EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(1));
-    v->updateFirstUsedGeneration();
-    EXPECT_EQUAL(v->getFirstUsedGen(), unsigned(2));
+    EXPECT_EQUAL(v->oldest_used_gen(), unsigned(1));
+    v->update_oldest_used_generation();
+    EXPECT_EQUAL(v->oldest_used_gen(), unsigned(2));
     EXPECT_EQUAL(v->getGen(), unsigned(2));
 }
 
diff --git a/searchlib/src/tests/attribute/document_weight_or_filter_search/document_weight_or_filter_search_test.cpp b/searchlib/src/tests/attribute/document_weight_or_filter_search/document_weight_or_filter_search_test.cpp
index e27065f1c25..0635b86121a 100644
--- a/searchlib/src/tests/attribute/document_weight_or_filter_search/document_weight_or_filter_search_test.cpp
+++ b/searchlib/src/tests/attribute/document_weight_or_filter_search/document_weight_or_filter_search_test.cpp
@@ -145,8 +145,8 @@ DocumentWeightOrFilterSearchTest::inc_generation()
     _postings.freeze();
     _postings.transferHoldLists(_gens.getCurrentGeneration());
     _gens.incGeneration();
-    _gens.updateFirstUsedGeneration();
-    _postings.trimHoldLists(_gens.getFirstUsedGeneration());
+    _gens.update_oldest_used_generation();
+    _postings.trimHoldLists(_gens.get_oldest_used_generation());
 }
 
 TEST_F(DocumentWeightOrFilterSearchTest, daat_or)
diff --git a/searchlib/src/tests/attribute/enum_comparator/enum_comparator_test.cpp b/searchlib/src/tests/attribute/enum_comparator/enum_comparator_test.cpp
index 1d76473754f..b957c31c7dc 100644
--- a/searchlib/src/tests/attribute/enum_comparator/enum_comparator_test.cpp
+++ b/searchlib/src/tests/attribute/enum_comparator/enum_comparator_test.cpp
@@ -149,7 +149,7 @@ TEST("requireThatComparatorWithTreeIsWorking")
     m.freeze();
     m.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    m.trimHoldLists(g.getFirstUsedGeneration());
+    m.trimHoldLists(g.get_oldest_used_generation());
 }
 
 TEST("requireThatFoldedLessIsWorking")
diff --git a/searchlib/src/tests/attribute/imported_attribute_vector/imported_attribute_vector_test.cpp b/searchlib/src/tests/attribute/imported_attribute_vector/imported_attribute_vector_test.cpp
index b9f3c23213e..0d2ce048111 100644
--- a/searchlib/src/tests/attribute/imported_attribute_vector/imported_attribute_vector_test.cpp
+++ b/searchlib/src/tests/attribute/imported_attribute_vector/imported_attribute_vector_test.cpp
@@ -73,14 +73,14 @@ TEST_F("makeReadGuard(false) acquires guards on both target and reference attrib
         EXPECT_EQUAL(2u, f.target_attr->getCurrentGeneration());
         EXPECT_EQUAL(2u, f.reference_attr->getCurrentGeneration());
         // Should still be holding guard for first generation of writes for both attributes
-        EXPECT_EQUAL(1u, f.target_attr->getFirstUsedGeneration());
-        EXPECT_EQUAL(1u, f.reference_attr->getFirstUsedGeneration());
+        EXPECT_EQUAL(1u, f.target_attr->get_oldest_used_generation());
+        EXPECT_EQUAL(1u, f.reference_attr->get_oldest_used_generation());
     }
     // Force a generation handler update
     add_n_docs_with_undefined_values(*f.reference_attr, 1);
     add_n_docs_with_undefined_values(*f.target_attr, 1);
-    EXPECT_EQUAL(3u, f.target_attr->getFirstUsedGeneration());
-    EXPECT_EQUAL(3u, f.reference_attr->getFirstUsedGeneration());
+    EXPECT_EQUAL(3u, f.target_attr->get_oldest_used_generation());
+    EXPECT_EQUAL(3u, f.reference_attr->get_oldest_used_generation());
 }
 
 TEST_F("makeReadGuard(true) acquires enum guard on target and regular guard on reference attribute", Fixture) {
@@ -95,15 +95,15 @@ TEST_F("makeReadGuard(true) acquires enum guard on target and regular guard on r
         EXPECT_EQUAL(5u, f.target_attr->getCurrentGeneration());
         EXPECT_EQUAL(2u, f.reference_attr->getCurrentGeneration());
 
-        EXPECT_EQUAL(3u, f.target_attr->getFirstUsedGeneration());
-        EXPECT_EQUAL(1u, f.reference_attr->getFirstUsedGeneration());
+        EXPECT_EQUAL(3u, f.target_attr->get_oldest_used_generation());
+        EXPECT_EQUAL(1u, f.reference_attr->get_oldest_used_generation());
         EXPECT_TRUE(has_active_enum_guards(*f.target_attr));
     }
     // Force a generation handler update
     add_n_docs_with_undefined_values(*f.reference_attr, 1);
     add_n_docs_with_undefined_values(*f.target_attr, 1);
-    EXPECT_EQUAL(7u, f.target_attr->getFirstUsedGeneration());
-    EXPECT_EQUAL(3u, f.reference_attr->getFirstUsedGeneration());
+    EXPECT_EQUAL(7u, f.target_attr->get_oldest_used_generation());
+    EXPECT_EQUAL(3u, f.reference_attr->get_oldest_used_generation());
     EXPECT_FALSE(has_active_enum_guards(*f.target_attr));
 }
 
diff --git a/searchlib/src/tests/attribute/posting_store/posting_store_test.cpp b/searchlib/src/tests/attribute/posting_store/posting_store_test.cpp
index 36babec6a89..a2d04488003 100644
--- a/searchlib/src/tests/attribute/posting_store/posting_store_test.cpp
+++ b/searchlib/src/tests/attribute/posting_store/posting_store_test.cpp
@@ -67,8 +67,8 @@ protected:
         _value_store.transfer_hold_lists(_gen_handler.getCurrentGeneration());
         _store.transferHoldLists(_gen_handler.getCurrentGeneration());
         _gen_handler.incGeneration();
-        _value_store.trim_hold_lists(_gen_handler.getFirstUsedGeneration());
-        _store.trimHoldLists(_gen_handler.getFirstUsedGeneration());
+        _value_store.trim_hold_lists(_gen_handler.get_oldest_used_generation());
+        _store.trimHoldLists(_gen_handler.get_oldest_used_generation());
     }
 
     EntryRef add_sequence(int start_key, int end_key)
diff --git a/searchlib/src/tests/attribute/postinglist/postinglist.cpp b/searchlib/src/tests/attribute/postinglist/postinglist.cpp
index 54efb3261c8..9e3ea72045f 100644
--- a/searchlib/src/tests/attribute/postinglist/postinglist.cpp
+++ b/searchlib/src/tests/attribute/postinglist/postinglist.cpp
@@ -263,8 +263,8 @@ AttributePostingListTest::freeTree(bool verbose)
     _intPostings->clearBuilder();
     _intPostings->transferHoldLists(_handler.getCurrentGeneration());
     _handler.incGeneration();
-    _intNodeAlloc->trimHoldLists(_handler.getFirstUsedGeneration());
-    _intPostings->trimHoldLists(_handler.getFirstUsedGeneration());
+    _intNodeAlloc->trimHoldLists(_handler.get_oldest_used_generation());
+    _intPostings->trimHoldLists(_handler.get_oldest_used_generation());
     LOG(info,
         "freeTree after unhold: %" PRIu64 " (%" PRIu64 " held)",
         static_cast<uint64_t>(_intNodeAlloc->getMemoryUsage().allocatedBytes()),
@@ -615,7 +615,7 @@ AttributePostingListTest::doCompactEnumStore(Tree &tree,
     generation_t generation = _handler.getCurrentGeneration();
     valueHandle.transferHoldLists(generation);
     _handler.incGeneration();
-    valueHandle.trimHoldLists(_handler.getFirstUsedGeneration());
+    valueHandle.trimHoldLists(_handler.get_oldest_used_generation());
 
     LOG(info,
         "doCompactEnumStore done");
@@ -672,8 +672,8 @@ removeOldGenerations(Tree &tree,
 {
     (void) tree;
     (void) valueHandle;
-    postingsAlloc.trimHoldLists(_handler.getFirstUsedGeneration());
-    postings.trimHoldLists(_handler.getFirstUsedGeneration());
+    postingsAlloc.trimHoldLists(_handler.get_oldest_used_generation());
+    postings.trimHoldLists(_handler.get_oldest_used_generation());
 }
 
 int
diff --git a/searchlib/src/tests/tensor/hnsw_index/hnsw_index_test.cpp b/searchlib/src/tests/tensor/hnsw_index/hnsw_index_test.cpp
index 7877b488065..1ebef22bab7 100644
--- a/searchlib/src/tests/tensor/hnsw_index/hnsw_index_test.cpp
+++ b/searchlib/src/tests/tensor/hnsw_index/hnsw_index_test.cpp
@@ -101,8 +101,8 @@ public:
     void commit() {
         index->transfer_hold_lists(gen_handler.getCurrentGeneration());
         gen_handler.incGeneration();
-        gen_handler.updateFirstUsedGeneration();
-        index->trim_hold_lists(gen_handler.getFirstUsedGeneration());
+        gen_handler.update_oldest_used_generation();
+        index->trim_hold_lists(gen_handler.get_oldest_used_generation());
     }
     void set_filter(std::vector<uint32_t> docids) {
         uint32_t sz = 10;
diff --git a/searchlib/src/tests/tensor/hnsw_index/stress_hnsw_mt.cpp b/searchlib/src/tests/tensor/hnsw_index/stress_hnsw_mt.cpp
index d559fa592ad..69a454e92cb 100644
--- a/searchlib/src/tests/tensor/hnsw_index/stress_hnsw_mt.cpp
+++ b/searchlib/src/tests/tensor/hnsw_index/stress_hnsw_mt.cpp
@@ -269,8 +269,8 @@ public:
     void commit(uint32_t docid) {
         index->transfer_hold_lists(gen_handler.getCurrentGeneration());
         gen_handler.incGeneration();
-        gen_handler.updateFirstUsedGeneration();
-        index->trim_hold_lists(gen_handler.getFirstUsedGeneration());
+        gen_handler.update_oldest_used_generation();
+        index->trim_hold_lists(gen_handler.get_oldest_used_generation());
         std::lock_guard<std::mutex> guard(in_progress_lock);
         in_progress->clearBit(docid);
         // printf("commit: %u\n", docid);
diff --git a/searchlib/src/vespa/searchlib/attribute/attributevector.cpp b/searchlib/src/vespa/searchlib/attribute/attributevector.cpp
index 963285d760d..876830bb186 100644
--- a/searchlib/src/vespa/searchlib/attribute/attributevector.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/attributevector.cpp
@@ -409,8 +409,8 @@ bool AttributeVector::applyWeight(DocId, const FieldValue&, const AssignValueUpd
 
 void
 AttributeVector::removeAllOldGenerations() {
-    _genHandler.updateFirstUsedGeneration();
-    removeOldGenerations(_genHandler.getFirstUsedGeneration());
+    _genHandler.update_oldest_used_generation();
+    removeOldGenerations(_genHandler.get_oldest_used_generation());
 }
 
 
@@ -483,14 +483,12 @@ AttributeVector::compactLidSpace(uint32_t wantedLidLimit) {
     incGeneration();
 }
 
-
 bool
 AttributeVector::canShrinkLidSpace() const {
     return wantShrinkLidSpace() &&
-        _compactLidSpaceGeneration.load(std::memory_order_relaxed) < getFirstUsedGeneration();
+        _compactLidSpaceGeneration.load(std::memory_order_relaxed) < get_oldest_used_generation();
 }
 
-
 void
 AttributeVector::shrinkLidSpace()
 {
diff --git a/searchlib/src/vespa/searchlib/attribute/attributevector.h b/searchlib/src/vespa/searchlib/attribute/attributevector.h
index f245a216aeb..4d4cd8ac35f 100644
--- a/searchlib/src/vespa/searchlib/attribute/attributevector.h
+++ b/searchlib/src/vespa/searchlib/attribute/attributevector.h
@@ -158,8 +158,8 @@ public:
     void incGeneration();
     void removeAllOldGenerations();
 
-    generation_t getFirstUsedGeneration() const {
-        return _genHandler.getFirstUsedGeneration();
+    generation_t get_oldest_used_generation() const {
+        return _genHandler.get_oldest_used_generation();
     }
 
     generation_t getCurrentGeneration() const {
@@ -466,8 +466,8 @@ public:
     /**
      * Should be called by the writer thread.
      */
-    void updateFirstUsedGeneration() {
-        _genHandler.updateFirstUsedGeneration();
+    void update_oldest_used_generation() {
+        _genHandler.update_oldest_used_generation();
     }
 
     /**
diff --git a/searchlib/src/vespa/searchlib/docstore/logdatastore.cpp b/searchlib/src/vespa/searchlib/docstore/logdatastore.cpp
index 7036ef238b6..cdf7e5f5ea8 100644
--- a/searchlib/src/vespa/searchlib/docstore/logdatastore.cpp
+++ b/searchlib/src/vespa/searchlib/docstore/logdatastore.cpp
@@ -109,8 +109,8 @@ LogDataStore::~LogDataStore()
 {
     // Must be called before ending threads as there are sanity checks.
     _fileChunks.clear();
-    _genHandler.updateFirstUsedGeneration();
-    _lidInfo.removeOldGenerations(_genHandler.getFirstUsedGeneration());
+    _genHandler.update_oldest_used_generation();
+    _lidInfo.removeOldGenerations(_genHandler.get_oldest_used_generation());
 }
 
 void
@@ -485,8 +485,8 @@ void LogDataStore::compactFile(FileId fileId)
     FileChunk::UP toDie;
     for (;;) {
         MonitorGuard guard(_updateLock);
-        _genHandler.updateFirstUsedGeneration();
-        if (currentGeneration < _genHandler.getFirstUsedGeneration()) {
+        _genHandler.update_oldest_used_generation();
+        if (currentGeneration < _genHandler.get_oldest_used_generation()) {
             if (_holdFileChunks[fc->getFileId().getId()] == 0u) {
                 toDie = std::move(fc);
                 break;
@@ -939,8 +939,8 @@ LogDataStore::setLid(const MonitorGuard &guard, uint32_t lid, const LidInfo &met
 {
     (void) guard;
     if (lid < _lidInfo.size()) {
-        _genHandler.updateFirstUsedGeneration();
-        _lidInfo.removeOldGenerations(_genHandler.getFirstUsedGeneration());
+        _genHandler.update_oldest_used_generation();
+        _lidInfo.removeOldGenerations(_genHandler.get_oldest_used_generation());
         const LidInfo prev = vespalib::atomic::load_ref_relaxed(_lidInfo[lid]);
         if (prev.valid()) {
             _fileChunks[prev.getFileId()]->remove(lid, prev.size());
@@ -958,8 +958,8 @@ LogDataStore::incGeneration()
 {
     _lidInfo.setGeneration(_genHandler.getNextGeneration());
     _genHandler.incGeneration();
-    _genHandler.updateFirstUsedGeneration();
-    _lidInfo.removeOldGenerations(_genHandler.getFirstUsedGeneration());
+    _genHandler.update_oldest_used_generation();
+    _lidInfo.removeOldGenerations(_genHandler.get_oldest_used_generation());
 }
 
 size_t
@@ -1213,7 +1213,7 @@ LogDataStore::canShrinkLidSpace(const MonitorGuard &) const
 {
     // Update lock is held, allowing call to _lidInfo.get_size()
     return getDocIdLimit() < _lidInfo.get_size() &&
-           _compactLidSpaceGeneration < _genHandler.getFirstUsedGeneration();
+           _compactLidSpaceGeneration < _genHandler.get_oldest_used_generation();
 }
 
 size_t
diff --git a/searchlib/src/vespa/searchlib/memoryindex/field_index.h b/searchlib/src/vespa/searchlib/memoryindex/field_index.h
index fb02ed880b4..bd087c8eae1 100644
--- a/searchlib/src/vespa/searchlib/memoryindex/field_index.h
+++ b/searchlib/src/vespa/searchlib/memoryindex/field_index.h
@@ -54,7 +54,7 @@ private:
 
     void trimHoldLists() {
         GenerationHandler::generation_t usedGen =
-            _generationHandler.getFirstUsedGeneration();
+                _generationHandler.get_oldest_used_generation();
         _postingListStore.trimHoldLists(usedGen);
         _dict.getAllocator().trimHoldLists(usedGen);
         _featureStore.trimHoldLists(usedGen);
diff --git a/searchlib/src/vespa/searchlib/test/fakedata/fakememtreeocc.cpp b/searchlib/src/vespa/searchlib/test/fakedata/fakememtreeocc.cpp
index 6e86d70fe52..e13d746df49 100644
--- a/searchlib/src/vespa/searchlib/test/fakedata/fakememtreeocc.cpp
+++ b/searchlib/src/vespa/searchlib/test/fakedata/fakememtreeocc.cpp
@@ -184,7 +184,7 @@ FakeMemTreeOccMgr::incGeneration()
 void
 FakeMemTreeOccMgr::trimHoldLists()
 {
-    _allocator.trimHoldLists(_generationHandler.getFirstUsedGeneration());
+    _allocator.trimHoldLists(_generationHandler.get_oldest_used_generation());
 }
 
 
diff --git a/storage/src/vespa/storage/bucketdb/generic_btree_bucket_database.hpp b/storage/src/vespa/storage/bucketdb/generic_btree_bucket_database.hpp
index 9db36e96fc0..f3a16f5826e 100644
--- a/storage/src/vespa/storage/bucketdb/generic_btree_bucket_database.hpp
+++ b/storage/src/vespa/storage/bucketdb/generic_btree_bucket_database.hpp
@@ -43,7 +43,7 @@ void GenericBTreeBucketDatabase<DataStoreTraitsT>::commit_tree_changes() {
 
     _generation_handler.incGeneration();
 
-    auto used_gen = _generation_handler.getFirstUsedGeneration();
+    auto used_gen = _generation_handler.get_oldest_used_generation();
     _store.trimHoldLists(used_gen);
     _tree.getAllocator().trimHoldLists(used_gen);
 }
diff --git a/vespalib/src/tests/btree/btree-stress/btree_stress_test.cpp b/vespalib/src/tests/btree/btree-stress/btree_stress_test.cpp
index 3ba7bf85e42..2c9455701f7 100644
--- a/vespalib/src/tests/btree/btree-stress/btree_stress_test.cpp
+++ b/vespalib/src/tests/btree/btree-stress/btree_stress_test.cpp
@@ -279,7 +279,7 @@ Fixture<Params>::commit()
     _values.transfer_hold_lists(current_gen);
     allocator.transferHoldLists(_generationHandler.getCurrentGeneration());
     _generationHandler.incGeneration();
-    auto first_used_gen = _generationHandler.getFirstUsedGeneration();
+    auto first_used_gen = _generationHandler.get_oldest_used_generation();
     allocator.trimHoldLists(first_used_gen);
     _keys.trim_hold_lists(first_used_gen);
     _values.trim_hold_lists(first_used_gen);
diff --git a/vespalib/src/tests/btree/btree_store/btree_store_test.cpp b/vespalib/src/tests/btree/btree_store/btree_store_test.cpp
index 4da34c64ed9..5196d08aa1b 100644
--- a/vespalib/src/tests/btree/btree_store/btree_store_test.cpp
+++ b/vespalib/src/tests/btree/btree_store/btree_store_test.cpp
@@ -33,7 +33,7 @@ protected:
         _store.freeze();
         _store.transferHoldLists(_gen_handler.getCurrentGeneration());
         _gen_handler.incGeneration();
-        _store.trimHoldLists(_gen_handler.getFirstUsedGeneration());
+        _store.trimHoldLists(_gen_handler.get_oldest_used_generation());
     }
 
     EntryRef add_sequence(int start_key, int end_key)
diff --git a/vespalib/src/tests/btree/btree_test.cpp b/vespalib/src/tests/btree/btree_test.cpp
index 3fd00a26189..8aeef40c957 100644
--- a/vespalib/src/tests/btree/btree_test.cpp
+++ b/vespalib/src/tests/btree/btree_test.cpp
@@ -165,7 +165,7 @@ cleanup(GenerationHandler & g, ManagerType & m)
     m.freeze();
     m.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    m.trimHoldLists(g.getFirstUsedGeneration());
+    m.trimHoldLists(g.get_oldest_used_generation());
 }
 
 template <typename ManagerType, typename NodeType>
@@ -876,7 +876,7 @@ TEST_F(BTreeTest, require_that_we_can_insert_and_remove_from_tree)
         manager.freeze();
         manager.transferHoldLists(g.getCurrentGeneration());
         g.incGeneration();
-        manager.trimHoldLists(g.getFirstUsedGeneration());
+        manager.trimHoldLists(g.get_oldest_used_generation());
     }
     // remove entries
     for (size_t i = 0; i < numEntries; ++i) {
@@ -1108,7 +1108,7 @@ TEST_F(BTreeTest, require_that_memory_usage_is_calculated)
     // trim hold lists
     tm.transferHoldLists(gh.getCurrentGeneration());
     gh.incGeneration();
-    tm.trimHoldLists(gh.getFirstUsedGeneration());
+    tm.trimHoldLists(gh.get_oldest_used_generation());
     mu = vespalib::MemoryUsage();
     mu.incAllocatedBytes(adjustAllocatedBytes(initialInternalNodes, sizeof(INode)));
     mu.incAllocatedBytes(adjustAllocatedBytes(initialLeafNodes, sizeof(LNode)));
@@ -1284,7 +1284,7 @@ TEST_F(BTreeTest, require_that_small_nodes_works)
     s.freeze();
     s.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    s.trimHoldLists(g.getFirstUsedGeneration());
+    s.trimHoldLists(g.get_oldest_used_generation());
 }
 
 namespace {
@@ -1418,7 +1418,7 @@ TEST_F(BTreeTest, require_that_apply_works)
     s.freeze();
     s.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    s.trimHoldLists(g.getFirstUsedGeneration());
+    s.trimHoldLists(g.get_oldest_used_generation());
 }
 
 class MyTreeTestIterator : public MyTree::Iterator
@@ -1555,7 +1555,7 @@ inc_generation(GenerationHandler &g, Tree &t)
     s.freeze();
     s.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    s.trimHoldLists(g.getFirstUsedGeneration());
+    s.trimHoldLists(g.get_oldest_used_generation());
 }
 
 template <typename Tree>
diff --git a/vespalib/src/tests/btree/btreeaggregation_test.cpp b/vespalib/src/tests/btree/btreeaggregation_test.cpp
index dff7de6660f..fbe8e4c8424 100644
--- a/vespalib/src/tests/btree/btreeaggregation_test.cpp
+++ b/vespalib/src/tests/btree/btreeaggregation_test.cpp
@@ -274,7 +274,7 @@ freezeTree(GenerationHandler &g, ManagerType &m)
     m.freeze();
     m.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    m.trimHoldLists(g.getFirstUsedGeneration());
+    m.trimHoldLists(g.get_oldest_used_generation());
 }
 
 template <typename ManagerType>
@@ -893,7 +893,7 @@ Test::requireThatWeCanInsertAndRemoveFromTree()
         manager.freeze();
         manager.transferHoldLists(g.getCurrentGeneration());
         g.incGeneration();
-        manager.trimHoldLists(g.getFirstUsedGeneration());
+        manager.trimHoldLists(g.get_oldest_used_generation());
     }
     // remove entries
     for (size_t i = 0; i < numEntries; ++i) {
@@ -1192,7 +1192,7 @@ Test::requireThatSmallNodesWorks()
     s.freeze();
     s.transferHoldLists(g.getCurrentGeneration());
     g.incGeneration();
-    s.trimHoldLists(g.getFirstUsedGeneration());
+    s.trimHoldLists(g.get_oldest_used_generation());
 }
 
 void
diff --git a/vespalib/src/tests/btree/frozenbtree_test.cpp b/vespalib/src/tests/btree/frozenbtree_test.cpp
index 01748b9edeb..e031b759f62 100644
--- a/vespalib/src/tests/btree/frozenbtree_test.cpp
+++ b/vespalib/src/tests/btree/frozenbtree_test.cpp
@@ -136,7 +136,7 @@ FrozenBTreeTest::freeTree(bool verbose)
     _allocator->freeze();
     _allocator->transferHoldLists(_generationHandler->getCurrentGeneration());
     _generationHandler->incGeneration();
-    _allocator->trimHoldLists(_generationHandler->getFirstUsedGeneration());
+    _allocator->trimHoldLists(_generationHandler->get_oldest_used_generation());
     delete _tree;
     _tree = NULL;
     delete _allocator;
diff --git a/vespalib/src/tests/datastore/fixed_size_hash_map/fixed_size_hash_map_test.cpp b/vespalib/src/tests/datastore/fixed_size_hash_map/fixed_size_hash_map_test.cpp
index ad10bc5c7e6..6abfaced867 100644
--- a/vespalib/src/tests/datastore/fixed_size_hash_map/fixed_size_hash_map_test.cpp
+++ b/vespalib/src/tests/datastore/fixed_size_hash_map/fixed_size_hash_map_test.cpp
@@ -92,9 +92,9 @@ DataStoreFixedSizeHashTest::commit()
     _hash_map->transfer_hold_lists(_generation_handler.getCurrentGeneration());
     _generation_holder.assign_generation(_generation_handler.getCurrentGeneration());
     _generation_handler.incGeneration();
-    _store.trimHoldLists(_generation_handler.getFirstUsedGeneration());
-    _hash_map->trim_hold_lists(_generation_handler.getFirstUsedGeneration());
-    _generation_holder.reclaim(_generation_handler.getFirstUsedGeneration());
+    _store.trimHoldLists(_generation_handler.get_oldest_used_generation());
+    _hash_map->trim_hold_lists(_generation_handler.get_oldest_used_generation());
+    _generation_holder.reclaim(_generation_handler.get_oldest_used_generation());
 }
 
 size_t
diff --git a/vespalib/src/tests/datastore/sharded_hash_map/sharded_hash_map_test.cpp b/vespalib/src/tests/datastore/sharded_hash_map/sharded_hash_map_test.cpp
index d6970e20e8a..67357d780bc 100644
--- a/vespalib/src/tests/datastore/sharded_hash_map/sharded_hash_map_test.cpp
+++ b/vespalib/src/tests/datastore/sharded_hash_map/sharded_hash_map_test.cpp
@@ -171,8 +171,8 @@ DataStoreShardedHashTest::commit()
     _store.transferHoldLists(_generationHandler.getCurrentGeneration());
     _hash_map.transfer_hold_lists(_generationHandler.getCurrentGeneration());
     _generationHandler.incGeneration();
-    _store.trimHoldLists(_generationHandler.getFirstUsedGeneration());
-    _hash_map.trim_hold_lists(_generationHandler.getFirstUsedGeneration());
+    _store.trimHoldLists(_generationHandler.get_oldest_used_generation());
+    _hash_map.trim_hold_lists(_generationHandler.get_oldest_used_generation());
 }
 
 void
diff --git a/vespalib/src/tests/datastore/unique_store_dictionary/unique_store_dictionary_test.cpp b/vespalib/src/tests/datastore/unique_store_dictionary/unique_store_dictionary_test.cpp
index d0fede5c550..5948303c335 100644
--- a/vespalib/src/tests/datastore/unique_store_dictionary/unique_store_dictionary_test.cpp
+++ b/vespalib/src/tests/datastore/unique_store_dictionary/unique_store_dictionary_test.cpp
@@ -64,7 +64,7 @@ struct UniqueStoreDictionaryTest : public ::testing::Test {
         dict.freeze();
         dict.transfer_hold_lists(gen_handler.getCurrentGeneration());
         gen_handler.incGeneration();
-        dict.trim_hold_lists(gen_handler.getFirstUsedGeneration());
+        dict.trim_hold_lists(gen_handler.get_oldest_used_generation());
     }
     void take_snapshot() {
         dict.freeze();
diff --git a/vespalib/src/tests/util/generationhandler/generationhandler_test.cpp b/vespalib/src/tests/util/generationhandler/generationhandler_test.cpp
index 00da752a749..0bc72f93a9d 100644
--- a/vespalib/src/tests/util/generationhandler/generationhandler_test.cpp
+++ b/vespalib/src/tests/util/generationhandler/generationhandler_test.cpp
@@ -26,10 +26,10 @@ GenerationHandlerTest::~GenerationHandlerTest() = default;
 TEST_F(GenerationHandlerTest, require_that_generation_can_be_increased)
 {
     EXPECT_EQ(0u, gh.getCurrentGeneration());
-    EXPECT_EQ(0u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(0u, gh.get_oldest_used_generation());
     gh.incGeneration();
     EXPECT_EQ(1u, gh.getCurrentGeneration());
-    EXPECT_EQ(1u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(1u, gh.get_oldest_used_generation());
 }
 
 TEST_F(GenerationHandlerTest, require_that_readers_can_take_guards)
@@ -87,34 +87,34 @@ TEST_F(GenerationHandlerTest, require_that_guards_can_be_copied)
 
 TEST_F(GenerationHandlerTest, require_that_the_first_used_generation_is_correct)
 {
-    EXPECT_EQ(0u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(0u, gh.get_oldest_used_generation());
     gh.incGeneration();
-    EXPECT_EQ(1u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(1u, gh.get_oldest_used_generation());
     {
         GenGuard g1 = gh.takeGuard();
         gh.incGeneration();
         EXPECT_EQ(1u, gh.getGenerationRefCount());
-        EXPECT_EQ(1u, gh.getFirstUsedGeneration());
+        EXPECT_EQ(1u, gh.get_oldest_used_generation());
     }
-    EXPECT_EQ(1u, gh.getFirstUsedGeneration());
-    gh.updateFirstUsedGeneration();	// Only writer should call this
+    EXPECT_EQ(1u, gh.get_oldest_used_generation());
+    gh.update_oldest_used_generation();	// Only writer should call this
     EXPECT_EQ(0u, gh.getGenerationRefCount());
-    EXPECT_EQ(2u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(2u, gh.get_oldest_used_generation());
     {
         GenGuard g1 = gh.takeGuard();
         gh.incGeneration();
         gh.incGeneration();
         EXPECT_EQ(1u, gh.getGenerationRefCount());
-        EXPECT_EQ(2u, gh.getFirstUsedGeneration());
+        EXPECT_EQ(2u, gh.get_oldest_used_generation());
         {
             GenGuard g2 = gh.takeGuard();
-            EXPECT_EQ(2u, gh.getFirstUsedGeneration());
+            EXPECT_EQ(2u, gh.get_oldest_used_generation());
         }
     }
-    EXPECT_EQ(2u, gh.getFirstUsedGeneration());
-    gh.updateFirstUsedGeneration();	// Only writer should call this
+    EXPECT_EQ(2u, gh.get_oldest_used_generation());
+    gh.update_oldest_used_generation();	// Only writer should call this
     EXPECT_EQ(0u, gh.getGenerationRefCount());
-    EXPECT_EQ(4u, gh.getFirstUsedGeneration());
+    EXPECT_EQ(4u, gh.get_oldest_used_generation());
 }
 
 TEST_F(GenerationHandlerTest, require_that_generation_can_grow_large)
@@ -124,7 +124,7 @@ TEST_F(GenerationHandlerTest, require_that_generation_can_grow_large)
         EXPECT_EQ(i, gh.getCurrentGeneration());
         guards.push_back(gh.takeGuard()); // take guard on current generation
         if (i >= 128) {
-            EXPECT_EQ(i - 128, gh.getFirstUsedGeneration());
+            EXPECT_EQ(i - 128, gh.get_oldest_used_generation());
             guards.pop_front();
             EXPECT_EQ(128u, gh.getGenerationRefCount());
         }
diff --git a/vespalib/src/tests/util/generationhandler_stress/generation_handler_stress_test.cpp b/vespalib/src/tests/util/generationhandler_stress/generation_handler_stress_test.cpp
index 74af25b54a8..fd2769fd8b1 100644
--- a/vespalib/src/tests/util/generationhandler_stress/generation_handler_stress_test.cpp
+++ b/vespalib/src/tests/util/generationhandler_stress/generation_handler_stress_test.cpp
@@ -238,7 +238,7 @@ Fixture::write_indirect_work(uint64_t cnt, IndirectContext& context)
     ReadStopper read_stopper(_stopRead);
     uint32_t sleep_cnt = 0;
     ASSERT_EQ(0, _generationHandler.getCurrentGeneration());
-    auto oldest_gen = _generationHandler.getFirstUsedGeneration();
+    auto oldest_gen = _generationHandler.get_oldest_used_generation();
     for (uint64_t i = 0; i < cnt; ++i) {
         auto gen = _generationHandler.getCurrentGeneration();
         // Hold data for gen, write new data for next_gen
@@ -248,7 +248,7 @@ Fixture::write_indirect_work(uint64_t cnt, IndirectContext& context)
         *v_ptr = next_gen;
         context._value_ptr.store(v_ptr, std::memory_order_release);
         _generationHandler.incGeneration();
-        auto first_used_gen = _generationHandler.getFirstUsedGeneration();
+        auto first_used_gen = _generationHandler.get_oldest_used_generation();
         while (oldest_gen < first_used_gen) {
             // Clear data that readers should no longer have access to.
             *context.calc_value_ptr(oldest_gen) = 0;
@@ -258,8 +258,8 @@ Fixture::write_indirect_work(uint64_t cnt, IndirectContext& context)
             // Sleep if writer gets too much ahead of readers.
             std::this_thread::sleep_for(1ms);
             ++sleep_cnt;
-            _generationHandler.updateFirstUsedGeneration();
-            first_used_gen = _generationHandler.getFirstUsedGeneration();
+            _generationHandler.update_oldest_used_generation();
+            first_used_gen = _generationHandler.get_oldest_used_generation();
         }
     }
     _doneWriteWork += cnt;
diff --git a/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp b/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
index c23065b7468..48fc88ec86d 100644
--- a/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
+++ b/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
@@ -434,7 +434,7 @@ StressFixture::commit()
     auto current_gen = generation_handler.getCurrentGeneration();
     g.assign_generation(current_gen);
     generation_handler.incGeneration();
-    auto first_used_gen = generation_handler.getFirstUsedGeneration();
+    auto first_used_gen = generation_handler.get_oldest_used_generation();
     g.reclaim(first_used_gen);
 }
 
diff --git a/vespalib/src/vespa/vespalib/util/generationhandler.cpp b/vespalib/src/vespa/vespalib/util/generationhandler.cpp
index d1cc0271068..3562926d88d 100644
--- a/vespalib/src/vespa/vespalib/util/generationhandler.cpp
+++ b/vespalib/src/vespa/vespalib/util/generationhandler.cpp
@@ -111,7 +111,7 @@ GenerationHandler::Guard::operator=(Guard &&rhs)
 }
 
 void
-GenerationHandler::updateFirstUsedGeneration()
+GenerationHandler::update_oldest_used_generation()
 {
     for (;;) {
         if (_first == _last.load(std::memory_order_relaxed))
@@ -125,12 +125,12 @@ GenerationHandler::updateFirstUsedGeneration()
         toFree->_next = _free;
         _free = toFree;
     }
-    _firstUsedGeneration.store(_first->_generation, std::memory_order_relaxed);
+    _oldest_used_generation.store(_first->_generation, std::memory_order_relaxed);
 }
 
 GenerationHandler::GenerationHandler()
     : _generation(0),
-      _firstUsedGeneration(0),
+      _oldest_used_generation(0),
       _last(nullptr),
       _first(nullptr),
       _free(nullptr),
@@ -144,7 +144,7 @@ GenerationHandler::GenerationHandler()
 
 GenerationHandler::~GenerationHandler(void)
 {
-    updateFirstUsedGeneration();
+    update_oldest_used_generation();
     assert(_first == _last.load(std::memory_order_relaxed));
     while (_free != nullptr) {
         GenerationHold *toFree = _free;
@@ -190,7 +190,7 @@ GenerationHandler::incGeneration()
         // reader
         set_generation(ngen);
         last->_generation.store(ngen, std::memory_order_relaxed);
-        updateFirstUsedGeneration();
+        update_oldest_used_generation();
         return;
     }
     GenerationHold *nhold = nullptr;
@@ -207,7 +207,7 @@ GenerationHandler::incGeneration()
     last->_next = nhold;
     set_generation(ngen);
     _last.store(nhold, std::memory_order_release);
-    updateFirstUsedGeneration();
+    update_oldest_used_generation();
 }
 
 uint32_t
@@ -215,7 +215,7 @@ GenerationHandler::getGenerationRefCount(generation_t gen) const
 {
     if (static_cast<sgeneration_t>(gen - getCurrentGeneration()) > 0)
         return 0u;
-    if (static_cast<sgeneration_t>(getFirstUsedGeneration() - gen) > 0)
+    if (static_cast<sgeneration_t>(get_oldest_used_generation() - gen) > 0)
         return 0u;
     for (GenerationHold *hold = _first; hold != nullptr; hold = hold->_next) {
         if (hold->_generation.load(std::memory_order_relaxed) == gen)
diff --git a/vespalib/src/vespa/vespalib/util/generationhandler.h b/vespalib/src/vespa/vespalib/util/generationhandler.h
index 9637ad0e414..6ba71b7f5fb 100644
--- a/vespalib/src/vespa/vespalib/util/generationhandler.h
+++ b/vespalib/src/vespa/vespalib/util/generationhandler.h
@@ -73,7 +73,7 @@ public:
 
 private:
     std::atomic<generation_t>     _generation;
-    std::atomic<generation_t>     _firstUsedGeneration;
+    std::atomic<generation_t>     _oldest_used_generation;
     std::atomic<GenerationHold *> _last;      // Points to "current generation" entry
     GenerationHold *_first;     // Points to "firstUsedGeneration" entry
     GenerationHold *_free;      // List of free entries
@@ -101,17 +101,17 @@ public:
     void incGeneration();
 
     /**
-     * Update first used generation.
+     * Update the oldest used generation.
      * Should be called by the writer thread.
      */
-    void updateFirstUsedGeneration();
+    void update_oldest_used_generation();
 
     /**
-     * Returns the first generation guarded by a reader.  It might be too low
-     * if writer hasn't updated first used generation after last reader left.
+     * Returns the oldest generation guarded by a reader.
+     * It might be too low if writer hasn't updated oldest used generation after last reader left.
      */
-    generation_t getFirstUsedGeneration() const noexcept {
-        return _firstUsedGeneration.load(std::memory_order_relaxed);
+    generation_t get_oldest_used_generation() const noexcept {
+        return _oldest_used_generation.load(std::memory_order_relaxed);
     }
 
     /**