more TDB

source/libs/tdb/src/db/tdbBtree.c

@@ -211,7 +211,7 @@ static int tdbBtCursorMoveToRoot(SBtCursor *pCur) {
   pBt = pCur->pBt;
   pPager = pBt->pPager;
 
-  pPage = tdbPagerGet(pPager, pBt->root);
+  pPage = tdbPagerGet(pPager, pBt->root, true);
   if (pPage == NULL) {
     // TODO: handle error
   }

source/libs/tdb/src/db/tdbPager.c

@@ -124,13 +124,15 @@ int tdbPagerOpenDB(SPager *pPager, SPgno *ppgno, bool toCreate) {
   return 0;
 }
 
-SPage *tdbPagerGet(SPager *pPager, SPgno pgno) {
+SPage *tdbPagerGet(SPager *pPager, SPgno pgno, bool toLoad) {
   SPgid  pgid;
   SPage *pPage;
+  int    ret;
 
   memcpy(pgid.fileid, pPager->fid, TDB_FILE_ID_LEN);
   pgid.pgno = pgno;
 
+  // Get page frame from the SPCache
   pPage = tdbPCacheFetch(pPager->pCache, &pgid, 1);
   if (pPage == NULL) {
     // TODO: handle error
@@ -138,6 +140,26 @@ SPage *tdbPagerGet(SPager *pPager, SPgno pgno) {
   }
   tdbPCacheFetchFinish(pPager->pCache, pPage);
 
+  // Zero the page or load page content from backend
+  // according to the options
+  if (pPage->pPager == NULL || !toLoad) {
+    if (!toLoad || pgno >= pPager->dbFileSize) {
+      memset(pPage->pData, 0, pPager->pageSize);
+    } else {
+      ret = tdbPagerReadPage(pPager, pPage);
+      if (ret < 0) {
+        // TODO: Need to drop the page
+        return NULL;
+      }
+    }
+
+    if (pPage->pPager) {
+      ASSERT(pPage->pPager == pPager);
+    } else {
+      pPage->pPager = pPager;
+    }
+  }
+
   return pPage;
 }
 
@@ -168,7 +190,7 @@ int tdbPagerAllocPage(SPager *pPager, SPage **ppPage, SPgno *ppgno) {
 
   if (1 /*TODO: no free page*/) {
     pgno = ++pPager->dbFileSize;
-    pPage = tdbPagerGet(pPager, pgno);
+    pPage = tdbPagerGet(pPager, pgno, false);
     ASSERT(pPage != NULL);
   } else {
     /* TODO: allocate from the free list */

source/libs/tdb/src/inc/tdbInt.h

@@ -132,6 +132,8 @@ typedef int (*FKeyComparator)(const void *pKey1, int kLen1, const void *pKey2, i
 
 #include "tdbPage.h"
 
+typedef struct SPager SPager;
+
 #include "tdbPCache.h"
 
 #include "tdbPager.h"

source/libs/tdb/src/inc/tdbPCache.h

@@ -37,7 +37,7 @@ struct SPage {
   SPage *  pLruNext;
   SPage *  pLruPrev;
   SPage *  pDirtyNext;
-  SPage *  pPager;
+  SPager * pPager;
 };
 
 int    tdbPCacheOpen(int pageSize, int cacheSize, int extraSize, SPCache **ppCache);

source/libs/tdb/src/inc/tdbPager.h

@@ -20,12 +20,10 @@
 extern "C" {
 #endif
 
-typedef struct SPager SPager;
-
 int    tdbPagerOpen(SPCache *pCache, const char *fileName, SPager **ppFile);
 int    tdbPagerClose(SPager *pFile);
 int    tdbPagerOpenDB(SPager *pFile, SPgno *ppgno, bool toCreate);
-SPage *tdbPagerGet(SPager *pFile, SPgno pgno);
+SPage *tdbPagerGet(SPager *pPager, SPgno pgno, bool toLoad);
 int    tdbPagerWrite(SPager *pFile, SPage *pPage);
 int    tdbPagerAllocPage(SPager *pFile, SPage **ppPage, SPgno *ppgno);
 int    tdbPagerBegin(SPager *pFile);