RCORE-1952 Fsa/string interning

src/realm/CMakeLists.txt

@@ -62,6 +62,8 @@ set(REALM_SOURCES
     table.cpp
     table_ref.cpp
     obj_list.cpp
+    string_interner.cpp
+    string_compressor.cpp
     object_id.cpp
     table_view.cpp
     tokenizer.cpp
@@ -178,6 +180,8 @@ set(REALM_INSTALL_HEADERS
     null.hpp
     obj.hpp
     obj_list.hpp
+    string_interner.hpp
+    string_compressor.hpp
     object_id.hpp
     path.hpp
     owned_data.hpp

src/realm/array.cpp

@@ -294,7 +294,7 @@ void Array::set_type(Type type)
     set_hasrefs_in_header(init_has_refs, header);
 }
 
-void Array::destroy_children(size_t offset) noexcept
+void Array::destroy_children(size_t offset, bool ro_only) noexcept
 {
     for (size_t i = offset; i != m_size; ++i) {
         int64_t value = get(i);
@@ -310,7 +310,7 @@ void Array::destroy_children(size_t offset) noexcept
             continue;
 
         ref_type ref = to_ref(value);
-        destroy_deep(ref, m_alloc);
+        destroy_deep(ref, m_alloc, ro_only);
     }
 }
 
@@ -607,6 +607,14 @@ void Array::do_ensure_minimum_width(int_fast64_t value)
     }
 }
 
+size_t Array::size() const noexcept
+{
+    // in case the array is in compressed format. Never read directly
+    // from the header the size, since it will result very likely in a cache miss.
+    // For compressed arrays m_size should always be kept updated, due to init_from_mem
+    return m_size;
+}
+
 bool Array::compress_array(Array& arr) const
 {
     if (m_integer_compressor.get_encoding() == NodeHeader::Encoding::WTypBits) {

src/realm/array.hpp

@@ -117,7 +117,7 @@ class Array : public Node, public ArrayParent {
     /// pointer.
     void init_from_mem(MemRef) noexcept;
 
-    /// Same as `init_from_ref(get_ref_from_parent())`.
+    /// Same as `init_from_ref(ref_from_parent())`.
     void init_from_parent() noexcept
     {
         ref_type ref = get_ref_from_parent();
@@ -210,6 +210,8 @@ class Array : public Node, public ArrayParent {
         update_width_cache_from_header();
     }
 
+    size_t size() const noexcept;
+
     bool is_empty() const noexcept
     {
         return size() == 0;
@@ -362,7 +364,8 @@ class Array : public Node, public ArrayParent {
     /// state (as if calling detach()), then free the allocated memory. If this
     /// accessor is already in the detached state, this function has no effect
     /// (idempotency).
-    void destroy_deep() noexcept;
+    /// If 'ro_only', only free space in read-only memory (the file)
+    void destroy_deep(bool ro_only = false) noexcept;
 
     /// check if the array is encoded (in B format)
     inline bool is_compressed() const;
@@ -377,13 +380,13 @@ class Array : public Node, public ArrayParent {
     bool try_decompress();
 
     /// Shorthand for `destroy_deep(MemRef(ref, alloc), alloc)`.
-    static void destroy_deep(ref_type ref, Allocator& alloc) noexcept;
+    static void destroy_deep(ref_type ref, Allocator& alloc, bool ro_only = false) noexcept;
 
     /// Destroy the specified array node and all of its children, recursively.
     ///
     /// This is done by freeing the specified array node after calling
     /// destroy_deep() for every contained 'ref' element.
-    static void destroy_deep(MemRef, Allocator&) noexcept;
+    static void destroy_deep(MemRef, Allocator&, bool ro_only = false) noexcept;
 
     // Clone deep
     static MemRef clone(MemRef, Allocator& from_alloc, Allocator& target_alloc);
@@ -546,7 +549,7 @@ class Array : public Node, public ArrayParent {
     // Overriding method in ArrayParent
     ref_type get_child_ref(size_t) const noexcept override;
 
-    void destroy_children(size_t offset = 0) noexcept;
+    void destroy_children(size_t offset = 0, bool ro_only = false) noexcept;
 
 protected:
     // Getters and Setters for adaptive-packed arrays
@@ -918,16 +921,17 @@ inline void Array::set_context_flag(bool value) noexcept
     }
 }
 
-inline void Array::destroy_deep() noexcept
+inline void Array::destroy_deep(bool ro_only) noexcept
 {
     if (!is_attached())
         return;
 
     if (m_has_refs)
-        destroy_children();
+        destroy_children(0, ro_only);
 
     char* header = get_header_from_data(m_data);
-    m_alloc.free_(m_ref, header);
+    if (!ro_only || is_read_only())
+        m_alloc.free_(m_ref, header);
     m_data = nullptr;
 }
 
@@ -970,20 +974,21 @@ inline void Array::clear_and_destroy_children()
     truncate_and_destroy_children(0);
 }
 
-inline void Array::destroy_deep(ref_type ref, Allocator& alloc) noexcept
+inline void Array::destroy_deep(ref_type ref, Allocator& alloc, bool ro_only) noexcept
 {
-    destroy_deep(MemRef(ref, alloc), alloc);
+    destroy_deep(MemRef(ref, alloc), alloc, ro_only);
 }
 
-inline void Array::destroy_deep(MemRef mem, Allocator& alloc) noexcept
+inline void Array::destroy_deep(MemRef mem, Allocator& alloc, bool ro_only) noexcept
 {
     if (!get_hasrefs_from_header(mem.get_addr())) {
-        alloc.free_(mem);
+        if (!ro_only || alloc.is_read_only(mem.get_ref()))
+            alloc.free_(mem);
         return;
     }
     Array array(alloc);
     array.init_from_mem(mem);
-    array.destroy_deep();
+    array.destroy_deep(ro_only);
 }
 
 

src/realm/array_integer.cpp

@@ -22,6 +22,8 @@
 #include <realm/impl/destroy_guard.hpp>
 #include <realm/column_integer.hpp>
 
+#include <iostream>
+
 using namespace realm;
 
 ArrayInteger::ArrayInteger(Allocator& allocator) noexcept

src/realm/array_integer.hpp

@@ -174,6 +174,7 @@ inline ArrayIntNull::~ArrayIntNull() noexcept {}
 
 inline size_t ArrayIntNull::size() const noexcept
 {
+    // this cannot be right, what if size is 0
     return Array::size() - 1;
 }
 

src/realm/array_string.cpp

@@ -17,6 +17,7 @@
  **************************************************************************/
 
 #include <realm/array_string.hpp>
+#include <realm/impl/array_writer.hpp>
 #include <realm/spec.hpp>
 #include <realm/mixed.hpp>
 
@@ -52,14 +53,24 @@ void ArrayString::init_from_mem(MemRef mem) noexcept
         else {
             auto arr = new (&m_storage) Array(m_alloc);
             arr->init_from_mem(mem);
-            m_string_enum_values = std::make_unique<ArrayString>(m_alloc);
-            ArrayParent* p;
-            REALM_ASSERT(m_spec != nullptr);
-            REALM_ASSERT(m_col_ndx != realm::npos);
-            ref_type r = m_spec->get_enumkeys_ref(m_col_ndx, p);
-            m_string_enum_values->init_from_ref(r);
-            m_string_enum_values->set_parent(p, m_col_ndx);
-            m_type = Type::enum_strings;
+            // The context flag is used to indicate interned strings vs old enum strings
+            // (in conjunction with has_refs() == false)
+            if (arr->get_context_flag_from_header(arr->get_header())) {
+                // init for new interned strings (replacing old enum strings)
+                m_type = Type::interned_strings;
+                // consider if we want this invariant: REALM_ASSERT_DEBUG(m_string_interner);
+            }
+            else {
+                // init for old enum strings
+                m_string_enum_values = std::make_unique<ArrayString>(m_alloc);
+                ArrayParent* p;
+                REALM_ASSERT(m_spec != nullptr);
+                REALM_ASSERT(m_col_ndx != realm::npos);
+                ref_type r = m_spec->get_enumkeys_ref(m_col_ndx, p);
+                m_string_enum_values->init_from_ref(r);
+                m_string_enum_values->set_parent(p, m_col_ndx);
+                m_type = Type::enum_strings;
+            }
         }
     }
     else {
@@ -111,6 +122,7 @@ size_t ArrayString::size() const
         case Type::big_strings:
             return static_cast<ArrayBigBlobs*>(m_arr)->size();
         case Type::enum_strings:
+        case Type::interned_strings:
             return static_cast<Array*>(m_arr)->size();
     }
     return {};
@@ -128,7 +140,8 @@ void ArrayString::add(StringData value)
         case Type::big_strings:
             static_cast<ArrayBigBlobs*>(m_arr)->add_string(value);
             break;
-        case Type::enum_strings: {
+        case Type::enum_strings:
+        case Type::interned_strings: {
             auto a = static_cast<Array*>(m_arr);
             size_t ndx = a->size();
             a->add(0);
@@ -150,6 +163,11 @@ void ArrayString::set(size_t ndx, StringData value)
         case Type::big_strings:
             static_cast<ArrayBigBlobs*>(m_arr)->set_string(ndx, value);
             break;
+        case Type::interned_strings: {
+            auto id = m_string_interner->intern(value);
+            static_cast<Array*>(m_arr)->set(ndx, id);
+            break;
+        }
         case Type::enum_strings: {
             size_t sz = m_string_enum_values->size();
             size_t res = m_string_enum_values->find_first(value, 0, sz);
@@ -178,6 +196,12 @@ void ArrayString::insert(size_t ndx, StringData value)
         case Type::enum_strings: {
             static_cast<Array*>(m_arr)->insert(ndx, 0);
             set(ndx, value);
+            break;
+        }
+        case Type::interned_strings: {
+            static_cast<Array*>(m_arr)->insert(ndx, 0);
+            set(ndx, value);
+            break;
         }
     }
 }
@@ -195,6 +219,10 @@ StringData ArrayString::get(size_t ndx) const
             size_t index = size_t(static_cast<Array*>(m_arr)->get(ndx));
             return m_string_enum_values->get(index);
         }
+        case Type::interned_strings: {
+            size_t id = size_t(static_cast<Array*>(m_arr)->get(ndx));
+            return m_string_interner->get(id);
+        }
     }
     return {};
 }
@@ -212,6 +240,10 @@ StringData ArrayString::get_legacy(size_t ndx) const
             size_t index = size_t(static_cast<Array*>(m_arr)->get(ndx));
             return m_string_enum_values->get(index);
         }
+        case Type::interned_strings: {
+            size_t id = size_t(static_cast<Array*>(m_arr)->get(ndx));
+            return m_string_interner->get(id);
+        }
     }
     return {};
 }
@@ -231,8 +263,12 @@ bool ArrayString::is_null(size_t ndx) const
         case Type::big_strings:
             return static_cast<ArrayBigBlobs*>(m_arr)->is_null(ndx);
         case Type::enum_strings: {
-            size_t index = size_t(static_cast<Array*>(m_arr)->get(ndx));
-            return m_string_enum_values->is_null(index);
+            size_t id = size_t(static_cast<Array*>(m_arr)->get(ndx));
+            return m_string_enum_values->is_null(id);
+        }
+        case Type::interned_strings: {
+            size_t id = size_t(static_cast<Array*>(m_arr)->get(ndx));
+            return id == 0;
         }
     }
     return {};
@@ -250,6 +286,7 @@ void ArrayString::erase(size_t ndx)
         case Type::big_strings:
             static_cast<ArrayBigBlobs*>(m_arr)->erase(ndx);
             break;
+        case Type::interned_strings:
         case Type::enum_strings:
             static_cast<Array*>(m_arr)->erase(ndx);
             break;
@@ -277,6 +314,9 @@ void ArrayString::move(ArrayString& dst, size_t ndx)
             // this operation will never be called for enumerated columns
             REALM_UNREACHABLE();
             break;
+        case Type::interned_strings:
+            m_arr->truncate(ndx);
+            break;
     }
 }
 
@@ -293,6 +333,7 @@ void ArrayString::clear()
             static_cast<ArrayBigBlobs*>(m_arr)->clear();
             break;
         case Type::enum_strings:
+        case Type::interned_strings:
             static_cast<Array*>(m_arr)->clear();
             break;
     }
@@ -321,6 +362,15 @@ size_t ArrayString::find_first(StringData value, size_t begin, size_t end) const
             }
             break;
         }
+        case Type::interned_strings: {
+            // we need a way to avoid this lookup for each leaf array. The lookup must appear
+            // higher up the call stack and passed down.
+            auto id = m_string_interner->lookup(value);
+            if (id) {
+                return static_cast<Array*>(m_arr)->find_first(*id, begin, end);
+            }
+            break;
+        }
     }
     return not_found;
 }
@@ -371,6 +421,9 @@ size_t ArrayString::lower_bound(StringData value)
             return lower_bound_string(static_cast<ArrayBigBlobs*>(m_arr), value);
         case Type::enum_strings:
             break;
+        case Type::interned_strings:
+            REALM_UNREACHABLE();
+            break;
     }
     return realm::npos;
 }
@@ -383,6 +436,9 @@ ArrayString::Type ArrayString::upgrade_leaf(size_t value_size)
     if (m_type == Type::enum_strings)
         return Type::enum_strings;
 
+    if (m_type == Type::interned_strings)
+        return Type::interned_strings;
+
     if (m_type == Type::medium_strings) {
         if (value_size <= medium_string_max_size)
             return Type::medium_strings;
@@ -473,8 +529,25 @@ void ArrayString::verify() const
             static_cast<ArrayBigBlobs*>(m_arr)->verify();
             break;
         case Type::enum_strings:
+        case Type::interned_strings:
             static_cast<Array*>(m_arr)->verify();
             break;
     }
 #endif
 }
+
+ref_type ArrayString::write(_impl::ArrayWriterBase& out, StringInterner* interner)
+{
+    REALM_ASSERT(interner);
+    // we have to write out all, modified or not, to match the total cleanup
+    Array interned(Allocator::get_default());
+    auto sz = size();
+    interned.create(NodeHeader::type_Normal, true, sz);
+    for (size_t i = 0; i < sz; ++i) {
+        interned.set(i, interner->intern(get(i)));
+    }
+    auto retval = interned.write(out, false, false, out.compress);
+    interned.destroy();
+    return retval;
+    // return m_arr->write(out, true, false, false);
+}