re-organize code

Author: Banyc

README.md

@@ -56,6 +56,10 @@ exit
 
 ## Spec
 
+### Database File Format
+
+The database file format mimicked that of SQLite but with some differences. 
+
 ### 数据类型
 
 只要求支持三种基本数据类型：int，char(n)，float，其中char(n)满足 1 <= n <= 255 。
@@ -78,7 +82,7 @@ exit
 
 ## Architecture
 
-![](img/2020-06-15-21-29-42.png)
+![](img/2020-06-16-14-33-06.png)
 
 ### Interpreter
 

img/2020-06-15-21-29-42.png

@@ -160,8 +160,6 @@ private SelectResult HandleSelectStatement(SelectStatement statement)
                     {
                         isIndexTreeAvailable = true;
                         // find out the primary key
-                        // List<AtomValue> indexPrimaryKeyPair = _recordManager.SelectRecord(statement.Condition.Ands[indexSchema.Name].RightOperand.ConcreteValue, indexSchema.RootPage);
-                        // primaryKey = indexPrimaryKeyPair[1];
                         List<AtomValue> wrappedPrimaryKey = _recordManager.SelectRecord(statement.Condition.Ands[indexSchema.SQL.AttributeName].RightOperand.ConcreteValue, indexSchema.RootPage);
                         primaryKey = wrappedPrimaryKey?[0];
                         break;
@@ -190,8 +188,8 @@ private SelectResult HandleSelectStatement(SelectStatement statement)
                 }
                 else  // the primary key is null.
                 // if primaryKey is null, 
-                // it means from the index tree could not find the primary key.
-                // in order words, there is not a row with the condition existing in table tree.
+                // it means that from the index tree it could not find the primary key.
+                // in order words, there is not a row existing in the table tree satisfying the condition.
                 // thus, no need to visit the table tree
                 {
                     // assign an empty list

img/2020-06-16-14-33-06.png

@@ -37,7 +37,6 @@ public View(IIndexManager bTreeController, IInterpreter interpreter, ICatalogMan
             _bTreeController = bTreeController;
             _interpreter = interpreter;
             _catalogManager = catalogManager;
-            // IIndexManager indexManager = new IndexManager();
             _recordManager = recordManager;
             _api = api;
         }

src/MiniSQL.Api/Api.cs

@@ -1,11 +1,7 @@
 using System;
-using System.Collections;
-using System.Collections.Generic;
-using MiniSQL.BufferManager.Controllers;
 using MiniSQL.BufferManager.Models;
-using MiniSQL.IndexManager.Models;
 
-namespace MiniSQL.IndexManager.Controllers
+namespace MiniSQL.BufferManager.Controllers
 {
     // a link list recording all free pages
     public class FreeList

src/MiniSQL.Api/Controllers/View.cs

@@ -170,7 +170,8 @@ public void WritePage(MemoryPage page)
 
             this.Stream.Seek((page.PageNumber - 1) * this.PageSize, SeekOrigin.Begin);
             this.Stream.Write(page.Data, 0, page.PageSize);
-            this.Stream.Flush(true);
+            // WORK AROUND: make good use of OS-level buffer XD
+            // this.Stream.Flush(true);
             page.IsDirty = false;
         }
 

src/MiniSQL.IndexManager/Controllers/FreeList.cs renamed to src/MiniSQL.BufferManager/Controllers/FreeList.cs

@@ -1,7 +1,6 @@
 using System;
-using MiniSQL.BufferManager.Models;
 
-namespace MiniSQL.IndexManager.Models
+namespace MiniSQL.BufferManager.Models
 {
     public class FreeListTruck
     {

src/MiniSQL.BufferManager/Controllers/Pager.cs

@@ -18,9 +18,57 @@ static void Main(string[] args)
 
             // TestPagerSwapping();
 
+            // TestFreeList();
+
             Console.WriteLine("[BufferManager] Test End");
         }
 
+        static void TestFreeList()
+        {
+            string dbPath = "./testdbfile.minidb";
+            File.Delete(dbPath);
+
+            Pager pager = new Pager(dbPath, 4096, 100);
+
+            List<MemoryPage> pageList = new List<MemoryPage>();
+            pageList.Add(pager.GetNewPage());  // page #2
+            pageList.Add(pager.GetNewPage());  // page #3
+            pageList.Add(pager.GetNewPage());  // page #4
+            pageList.Add(pager.GetNewPage());  // page #5
+
+            FreeList freeList = new FreeList(pager);
+
+            // test initialization
+            MemoryPage newPage = null;
+            newPage = freeList.AllocatePage();  // freeList is now empty
+            Debug.Assert(newPage == null);
+
+            // recycle pages
+            // MemoryPage tempPage = pager.ReadPage(3);
+            freeList.RecyclePage(pageList[2]);  // freeList->4
+            freeList.RecyclePage(pageList[1]);  // freeList->3->4
+            freeList.RecyclePage(pageList[3]);  // freeList->5->3->4
+
+            // fetch page from free list
+            newPage = freeList.AllocatePage();  // freeList->3->4
+            Debug.Assert(newPage.PageNumber == 5);
+            newPage = freeList.AllocatePage();  // freeList->4
+            Debug.Assert(newPage.PageNumber == 3);
+
+            // recycle a page
+            freeList.RecyclePage(pageList[3]);  // freeList->5->4
+
+            // fetch remaining pages
+            newPage = freeList.AllocatePage();  // freeList->4
+            Debug.Assert(newPage.PageNumber == 5);
+            newPage = freeList.AllocatePage();  // freeList->null
+            Debug.Assert(newPage.PageNumber == 4);
+            newPage = freeList.AllocatePage();  // freeList->null
+            Debug.Assert(newPage == null);
+
+            pager.Close();
+        }
+
         private static Expression GetAndsExpression()
         {
             // __tree structure__

src/MiniSQL.IndexManager/Models/FreeListTruck.cs renamed to src/MiniSQL.BufferManager/Models/FreeListTruck.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Runtime;
 using MiniSQL.BufferManager.Controllers;
 using MiniSQL.IndexManager.Models;
 using MiniSQL.BufferManager.Models;

src/MiniSQL.BufferManager/Program.cs

@@ -36,4 +36,5 @@ delete from person where age <= 20 and height < 170 and name = "Person16";
 
 select * from person;
 
-drop table persion;
+-- drop table persion;
+drop table person;