[FLASH-318/319/343/344] PageStorage: RefPages, MVCC && Snapshot read

dbms/CMakeLists.txt

@@ -59,6 +59,7 @@ add_headers_and_sources(dbms src/Storages/Distributed)
 add_headers_and_sources(dbms src/Storages/MergeTree)
 add_headers_and_sources(dbms src/Storages/Transaction)
 add_headers_and_sources(dbms src/Storages/Page)
+add_headers_and_sources(dbms src/Storages/Page/VersionSet)
 add_headers_and_sources(dbms src/Raft)
 add_headers_and_sources(dbms src/TiDB)
 add_headers_and_sources(dbms src/Client)

dbms/src/Common/ProfileEvents.cpp

@@ -162,6 +162,13 @@
     M(PSMWriteFailed) \
     M(PSMReadFailed) \
     \
+    M(PSMVCCApplyOnCurrentBase) \
+    M(PSMVCCApplyOnCurrentDelta) \
+    M(PSMVCCApplyOnNewDelta) \
+    M(PSMVCCCompactOnDelta) \
+    M(PSMVCCCompactOnDeltaRebaseRejected) \
+    M(PSMVCCCompactOnBase) \
+    \
     M(DMWriteBlock) \
     M(DMWriteBlockNS) \
     M(DMAppendDelta) \

dbms/src/IO/WriteHelpers.h

@@ -816,4 +816,12 @@ toString(const T & x, int precision)
     return ss.str();
 }
 
+/// Pointer to a string
+inline String ptrToString(const void * const p)
+{
+    std::stringstream ss;
+    ss << p;
+    return ss.str();
+}
+
 }

dbms/src/Storages/Page/Page.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <map>
 #include <unordered_map>
 
 #include <IO/BufferBase.h>
@@ -27,8 +28,8 @@ using Pages       = std::vector<Page>;
 using PageMap     = std::map<PageId, Page>;
 using PageHandler = std::function<void(PageId page_id, const Page &)>;
 
-// Indicate the page size && offset in PageFile. TODO: rename to `PageEntry`?
-struct PageCache
+// Indicate the page size && offset in PageFile.
+struct PageEntry
 {
     // if file_id == 0, means it is invalid
     PageFileId file_id  = 0;
@@ -37,15 +38,15 @@ struct PageCache
     UInt64     offset   = 0;
     UInt64     tag      = 0;
     UInt64     checksum = 0;
+    UInt32     ref      = 1; // for ref counting
 
-    bool               isValid() const { return file_id != 0; }
-    PageFileIdAndLevel fileIdLevel() const { return std::make_pair(file_id, level); }
+    inline bool               isValid() const { return file_id != 0; }
+    inline bool               isTombstone() const { return ref == 0; }
+    inline PageFileIdAndLevel fileIdLevel() const { return std::make_pair(file_id, level); }
 };
-static_assert(std::is_trivially_copyable_v<PageCache>);
+static_assert(std::is_trivially_copyable_v<PageEntry>);
 
-using PageCacheMap    = std::unordered_map<PageId, PageCache>;
-using PageCaches      = std::vector<PageCache>;
-using PageIdAndCache  = std::pair<PageId, PageCache>;
-using PageIdAndCaches = std::vector<PageIdAndCache>;
+using PageIdAndEntry   = std::pair<PageId, PageEntry>;
+using PageIdAndEntries = std::vector<PageIdAndEntry>;
 
 } // namespace DB

dbms/src/Storages/Page/PageDefines.h

@@ -3,6 +3,7 @@
 #include <unordered_set>
 #include <vector>
 
+#include <Core/Defines.h>
 #include <Core/Types.h>
 
 namespace DB