dht: auto_refreshing_sharder.hh: don't include database.hh

database.hh is a heavyweight include file with a lot of fan-in.
auto_refreshing_sharder.hh has a lot of fan out. The combination
means a large dependency load.

Deinline the class and use forward declarations to avoid the #include.

There is no expected performance impact because all the functions are
virtual.

Ref #1

Note: this shouldn't belong in dht, but be injected by a higher layer,
but this isn't addressed by the patch.

Closes scylladb/scylladb#21768

dht/auto_refreshing_sharder.hh

@@ -8,7 +8,15 @@
 
 #pragma once
 
-#include "replica/database.hh"
+#include "dht/sharder.hh"
+#include "locator/abstract_replication_strategy.hh"
+
+#include <seastar/core/abort_source.hh>
+#include <seastar/core/shared_ptr.hh>
+
+namespace replica {
+class table;
+}
 
 namespace dht {
 
@@ -27,41 +35,19 @@ class auto_refreshing_sharder : public dht::sharder {
     optimized_optional<seastar::abort_source::subscription> _callback;
     std::optional<write_replica_set_selector> _sel;
 private:
-    void refresh() {
-        _erm = _table->get_effective_replication_map();
-        _sharder = &_erm->get_sharder(*_table->schema());
-        _callback = _erm->get_validity_abort_source().subscribe([this] () noexcept {
-            refresh();
-        });
-    }
+    void refresh();
 public:
-    auto_refreshing_sharder(lw_shared_ptr<replica::table> table, std::optional<write_replica_set_selector> sel = std::nullopt)
-        : _table(std::move(table))
-        , _sel(sel)
-    {
-        refresh();
-    }
+    auto_refreshing_sharder(lw_shared_ptr<replica::table> table, std::optional<write_replica_set_selector> sel = std::nullopt);
 
-    virtual ~auto_refreshing_sharder() = default;
+    virtual ~auto_refreshing_sharder();
 
-    virtual unsigned shard_for_reads(const token& t) const override {
-        return _sharder->shard_for_reads(t);
-    }
+    virtual unsigned shard_for_reads(const token& t) const override;
 
-    virtual dht::shard_replica_set shard_for_writes(const token& t, std::optional<write_replica_set_selector> sel) const override {
-        if (!sel) {
-            sel = _sel;
-        }
-        return _sharder->shard_for_writes(t, sel);
-    }
+    virtual dht::shard_replica_set shard_for_writes(const token& t, std::optional<write_replica_set_selector> sel) const override;
 
-    virtual std::optional<dht::shard_and_token> next_shard_for_reads(const dht::token& t) const override {
-        return _sharder->next_shard_for_reads(t);
-    }
+    virtual std::optional<dht::shard_and_token> next_shard_for_reads(const dht::token& t) const override;
 
-    virtual dht::token token_for_next_shard_for_reads(const dht::token& t, shard_id shard, unsigned spans = 1) const override {
-        return _sharder->token_for_next_shard_for_reads(t, shard, spans);
-    }
+    virtual dht::token token_for_next_shard_for_reads(const dht::token& t, shard_id shard, unsigned spans = 1) const override;
 };
 
 } // namespace dht

dht/i_partitioner.cc

@@ -8,6 +8,7 @@
 
 #include "i_partitioner.hh"
 #include "sharder.hh"
+#include "auto_refreshing_sharder.hh"
 #include <seastar/core/seastar.hh>
 #include <seastar/coroutine/maybe_yield.hh>
 #include "dht/ring_position.hh"
@@ -15,6 +16,7 @@
 #include "utils/assert.hh"
 #include "utils/class_registrator.hh"
 #include "sstables/key.hh"
+#include "replica/database.hh"
 #include <seastar/core/thread.hh>
 #include <seastar/core/on_internal_error.hh>
 #include "utils/log.hh"
@@ -492,6 +494,46 @@ std::optional<shard_id> is_single_shard(const dht::sharder& sharder, const schem
     return shard;
 }
 
+auto_refreshing_sharder::auto_refreshing_sharder(lw_shared_ptr<replica::table> table, std::optional<write_replica_set_selector> sel)
+    : _table(std::move(table))
+    , _sel(sel)
+{
+    refresh();
+}
+
+auto_refreshing_sharder::~auto_refreshing_sharder() = default;
+
+void
+auto_refreshing_sharder::refresh() {
+    _erm = _table->get_effective_replication_map();
+    _sharder = &_erm->get_sharder(*_table->schema());
+    _callback = _erm->get_validity_abort_source().subscribe([this] () noexcept {
+        refresh();
+    });
+}
+
+unsigned auto_refreshing_sharder::shard_for_reads(const token& t) const {
+    return _sharder->shard_for_reads(t);
+}
+
+dht::shard_replica_set
+auto_refreshing_sharder::shard_for_writes(const token& t, std::optional<write_replica_set_selector> sel) const {
+    if (!sel) {
+        sel = _sel;
+    }
+    return _sharder->shard_for_writes(t, sel);
+}
+
+std::optional<dht::shard_and_token>
+auto_refreshing_sharder::next_shard_for_reads(const dht::token& t) const {
+    return _sharder->next_shard_for_reads(t);
+}
+
+dht::token
+auto_refreshing_sharder::token_for_next_shard_for_reads(const dht::token& t, shard_id shard, unsigned spans) const {
+    return _sharder->token_for_next_shard_for_reads(t, shard, spans);
+}
+
 }
 
 auto fmt::formatter<dht::ring_position_view>::format(const dht::ring_position_view& pos, fmt::format_context& ctx) const