No Unique PTRs for string interner and string compressor (#7807)

* No unique ptrs for string interner + limit number of interners

* point fix client-reset test

* code review

Author: nicola-cab

src/realm/array.cpp

@@ -314,18 +314,6 @@ void Array::destroy_children(size_t offset, bool ro_only) noexcept
     }
 }
 
-// size_t Array::get_byte_size() const noexcept
-//{
-//     const auto header = get_header();
-//     auto num_bytes = get_byte_size_from_header(header);
-//     auto read_only = m_alloc.is_read_only(m_ref) == true;
-//     auto capacity = get_capacity_from_header(header);
-//     auto bytes_ok = num_bytes <= capacity;
-//     REALM_ASSERT(read_only || bytes_ok);
-//     REALM_ASSERT_7(m_alloc.is_read_only(m_ref), ==, true, ||, num_bytes, <=, get_capacity_from_header(header));
-//     return num_bytes;
-// }
-
 ref_type Array::do_write_shallow(_impl::ArrayWriterBase& out) const
 {
     // here we might want to compress the array and write down.
@@ -607,14 +595,6 @@ 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

@@ -210,8 +210,6 @@ class Array : public Node, public ArrayParent {
         update_width_cache_from_header();
     }
 
-    size_t size() const noexcept;
-
     bool is_empty() const noexcept
     {
         return size() == 0;

src/realm/array_string.cpp

@@ -18,6 +18,7 @@
 
 #include <realm/array_string.hpp>
 #include <realm/impl/array_writer.hpp>
+#include <realm/string_interner.hpp>
 #include <realm/spec.hpp>
 #include <realm/mixed.hpp>
 
@@ -549,5 +550,4 @@ ref_type ArrayString::write(_impl::ArrayWriterBase& out, StringInterner* interne
     auto retval = interned.write(out, false, false, out.compress);
     interned.destroy();
     return retval;
-    // return m_arr->write(out, true, false, false);
 }

src/realm/node.hpp

@@ -21,7 +21,6 @@
 
 #include <realm/node_header.hpp>
 #include <realm/alloc.hpp>
-#include <realm/string_interner.hpp>
 
 #include <iostream>
 
@@ -352,6 +351,7 @@ class ArrayWriterBase;
 }
 
 /// Base class for all nodes holding user data
+class StringInterner;
 class ArrayPayload {
 public:
     virtual ~ArrayPayload();

src/realm/string_compressor.cpp

@@ -17,36 +17,35 @@
  **************************************************************************/
 
 #include <realm/string_compressor.hpp>
+#include <realm/string_interner.hpp>
 #include <realm/string_data.hpp>
 
-#include <realm/array_unsigned.hpp>
-
 #include <iostream>
 namespace realm {
 
 StringCompressor::StringCompressor(Allocator& alloc, Array& parent, size_t index, bool writable)
+    : m_data(alloc)
 {
     m_compression_map.resize(16); // start with a very small compression map
     m_symbols.reserve(65536);
-    m_data = std::make_unique<ArrayUnsigned>(alloc);
-    m_data->set_parent(&parent, index);
+    m_data.set_parent(&parent, index);
     refresh(writable);
 }
 
 void StringCompressor::refresh(bool writable)
 {
     // we assume that compressors are only created from a valid parent.
     // String interners in 'dead' mode should never instantiate a string compressor.
-    if (m_data->get_ref_from_parent() == 0) {
+    if (m_data.get_ref_from_parent() == 0) {
         REALM_ASSERT(writable);
-        m_data->create(0, 65535);
-        m_data->update_parent();
+        m_data.create(0, 65535);
+        m_data.update_parent();
     }
     else {
-        if (m_data->is_attached())
-            m_data->update_from_parent();
+        if (m_data.is_attached())
+            m_data.update_from_parent();
         else
-            m_data->init_from_ref(m_data->get_ref_from_parent());
+            m_data.init_from_ref(m_data.get_ref_from_parent());
     }
     rebuild_internal();
 }
@@ -111,7 +110,7 @@ void StringCompressor::expand_compression_map()
 
 void StringCompressor::rebuild_internal()
 {
-    auto num_symbols = m_data->size();
+    auto num_symbols = m_data.size();
     if (num_symbols == m_symbols.size())
         return;
     if (num_symbols < m_symbols.size()) {
@@ -132,7 +131,7 @@ void StringCompressor::rebuild_internal()
     }
     // we have new symbols to add
     for (size_t i = m_symbols.size(); i < num_symbols; ++i) {
-        auto pair = m_data->get(i);
+        auto pair = m_data.get(i);
         SymbolDef def;
         def.id = (CompressionSymbol)(i + 256);
         def.expansion_a = 0xFFFF & (pair >> 16);
@@ -198,13 +197,13 @@ CompressedString StringCompressor::compress(StringData sd, bool learn)
                 if (m_symbols.size() < (65536 - 256) && learn) {
                     // define a new symbol for this entry and use it.
                     REALM_ASSERT_DEBUG(m_compression_map[hash].id == 0);
-                    REALM_ASSERT_DEBUG(m_symbols.size() == m_data->size());
-                    REALM_ASSERT_DEBUG(m_data->is_attached());
+                    REALM_ASSERT_DEBUG(m_symbols.size() == m_data.size());
+                    REALM_ASSERT_DEBUG(m_data.is_attached());
                     CompressionSymbol id = (CompressionSymbol)(256 + m_symbols.size());
                     SymbolDef def{id, from[0], from[1]};
                     m_compression_map[hash] = def;
                     add_expansion(def);
-                    m_data->add(((uint64_t)from[0]) << 16 | from[1]);
+                    m_data.add(((uint64_t)from[0]) << 16 | from[1]);
                     // std::cerr << id << " = {" << from[0] << ", " << from[1] << "}" << std::endl;
                     *to++ = id;
                     from += 2;

src/realm/string_compressor.hpp

@@ -19,11 +19,13 @@
 #ifndef REALM_STRING_COMPRESSOR_HPP
 #define REALM_STRING_COMPRESSOR_HPP
 
+#include <realm/array_unsigned.hpp>
 #include <realm/utilities.hpp>
 #include <vector>
 
 using CompressionSymbol = uint16_t;
 using CompressedString = std::vector<CompressionSymbol>;
+
 struct CompressedStringView {
     CompressionSymbol* data = 0;
     uint32_t size = 0;
@@ -51,11 +53,6 @@ struct CompressedStringView {
 };
 
 namespace realm {
-
-class ArrayUnsigned;
-class Array;
-class Allocator;
-
 class StringCompressor {
 public:
     StringCompressor(Allocator& alloc, Array& parent, size_t index, bool writable);
@@ -90,7 +87,7 @@ class StringCompressor {
     std::vector<ExpandedSymbolDef> m_symbols; // map from symbol -> symbolpair, 2 elements pr entry
     std::vector<SymbolDef> m_compression_map; // perfect hash from symbolpair to its symbol
 
-    std::unique_ptr<ArrayUnsigned> m_data;
+    ArrayUnsigned m_data;
     constexpr static size_t storage_chunk_size = 4096;
     std::vector<std::string> m_expansion_storage;
 };