storage: rename delta() to offset_delta()

Just delta() isn't necessarily clear what it is a delta of.

src/v/archival/ntp_archiver_service.cc

@@ -1471,7 +1471,7 @@ ntp_archiver::do_schedule_single_upload(
     auto base = upload.starting_offset;
     auto log = _parent.log();
     auto delta = base - model::offset_cast(log->from_log_offset(base));
-    auto delta_offset_next = log->delta(
+    auto delta_offset_next = log->offset_delta(
       model::next_offset(upload.final_offset));
 
     // The upload is successful only if the segment, and tx_range are
@@ -2927,7 +2927,7 @@ ss::future<bool> ntp_archiver::do_upload_local(
     auto base = upload.starting_offset;
     auto log = _parent.log();
     auto delta = base - model::offset_cast(log->from_log_offset(base));
-    auto delta_offset_next = log->delta(
+    auto delta_offset_next = log->offset_delta(
       model::next_offset(upload.final_offset));
     auto archiver_term = _start_term;
 

src/v/raft/consensus.cc

@@ -2462,7 +2462,7 @@ consensus::do_write_snapshot(model::offset last_included_index, iobuf&& data) {
       .latest_configuration = *config,
       .cluster_time = clock_type::time_point::min(),
       .log_start_delta = offset_translator_delta(
-        _log->delta(model::next_offset(last_included_index))()),
+        _log->offset_delta(model::next_offset(last_included_index))()),
     };
 
     return details::persist_snapshot(

src/v/raft/recovery_stm.cc

@@ -490,7 +490,7 @@ recovery_stm::take_on_demand_snapshot(model::offset last_included_offset) {
       .last_included_term = *term,
       .latest_configuration = std::move(*cfg),
       .log_start_delta = offset_translator_delta(
-        _ptr->log()->delta(model::next_offset(last_included_offset))),
+        _ptr->log()->offset_delta(model::next_offset(last_included_offset))),
     };
 
     co_await writer.write_metadata(reflection::to_iobuf(std::move(metadata)));

src/v/raft/tests/raft_reconfiguration_test.cc

@@ -145,14 +145,15 @@ void assert_offset_translator_state_is_consistent(
     std::vector<int64_t> deltas;
     for (model::offset o :
          boost::irange<model::offset>(start_offset, dirty_offset)) {
-        deltas.push_back(first_raft->log()->delta(o));
+        deltas.push_back(first_raft->log()->offset_delta(o));
     }
 
     for (auto it = std::next(nodes.begin()); it != nodes.end(); ++it) {
         auto idx = 0;
         for (model::offset o :
              boost::irange<model::offset>(start_offset, dirty_offset)) {
-            ASSERT_EQ(it->second->raft()->log()->delta(o), deltas[idx++]);
+            ASSERT_EQ(
+              it->second->raft()->log()->offset_delta(o), deltas[idx++]);
         }
     }
 }

src/v/storage/disk_log_impl.cc

@@ -1425,7 +1425,7 @@ bool disk_log_impl::is_new_log() const {
            && os.start_offset == not_initialized;
 }
 
-model::offset_delta disk_log_impl::delta(model::offset o) const {
+model::offset_delta disk_log_impl::offset_delta(model::offset o) const {
     return model::offset_delta{_offset_translator.state()->delta(o)};
 }
 

src/v/storage/disk_log_impl.h

@@ -116,7 +116,7 @@ class disk_log_impl final : public log {
         return _offset_translator.state();
     }
     raft::offset_translator& offset_translator() { return _offset_translator; }
-    model::offset_delta delta(model::offset) const final;
+    model::offset_delta offset_delta(model::offset) const final;
     model::offset from_log_offset(model::offset) const final;
     model::offset to_log_offset(model::offset) const final;
     model::offset find_last_term_start_offset() const final;

src/v/storage/log.h

@@ -99,15 +99,15 @@ class log {
     virtual ss::future<std::optional<timequery_result>>
       timequery(timequery_config) = 0;
 
-    // Prefer to use delta() or from/to_log_offset().
+    // Prefer to use offset_delta() or from/to_log_offset().
     // TODO: remove direct access to the translator state and instead rely on
     // the translation/delta interface.
     virtual ss::lw_shared_ptr<const storage::offset_translator_state>
     get_offset_translator_state() const = 0;
 
     // Returns the offset delta for a given offset. This can be used for
     // example to translate a Raft offset to a data offset.
-    virtual model::offset_delta delta(model::offset) const = 0;
+    virtual model::offset_delta offset_delta(model::offset) const = 0;
 
     // Translate the given log offset into a data offset.
     virtual model::offset from_log_offset(model::offset) const = 0;