Further refinements to the virtual method implementation of

sqlite3PagerGet().

FossilOrigin-Name: 67df44464847b43f8c0b186157e31cc66c1e5796

diff --git a/manifest b/manifest
index 8e294defe8e2b00971068f78f7e039a567664d52..a88cc6c349331ae058735ac8762ac7b4f5fc8d18 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Make\sthe\ssqlite3PagerGet()\sinterface\sinto\sa\svirtual\smethod,\swith\sdifferent\nimplementations\sbased\son\sthe\scurrent\sstate\sof\sthe\spager.\s\sThis\sgives\sa\ssmall\nperformance\sincrease\sby\savoiding\sunnecessary\sbranches\sinside\sthe\svarious\nmethods.
-D 2016-12-13T14:32:47.273
+C Further\srefinements\sto\sthe\svirtual\smethod\simplementation\sof\s\nsqlite3PagerGet().
+D 2016-12-13T15:53:22.192
 F Makefile.in 7639c6a09da11a9c7c6f2630fc981ee588d1072d
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@ -375,7 +375,7 @@ F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
 F src/os_unix.c 30e2c43e4955db990e5b5a81e901f8aa74cc8820
 F src/os_win.c cf90abd4e50d9f56d2c20ce8e005aff55d7bd8e9
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c e99f7edfab2441f55fc1a4f4dd05f3bf0f1a82cd
+F src/pager.c 642b1968fdaa6219aa562ae17b9a3745dfca10f5
 F src/pager.h d1e944291030351f362a0a7da9b5c3e34e603e39
 F src/parse.y 29153738a7322054359320eb00b5a4cd44389f20
 F src/pcache.c 219fc5238d5c80e2990ab01e1459db3a96866447
@@ -1536,10 +1536,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 1a636d5e0eec0a4d968519d1dfd35a983e512c78
-R d5446ab8495308acac3b07699664fa42
-T *branch * pager-get-method
-T *sym-pager-get-method *
-T -sym-trunk *
+P df5bb90d208e0633056389e97696d260e3830e8d
+R f50bcbf9b53ee7a4a76924f315bdb191
 U drh
-Z 3a0d20f1bb36125dcd9d753c0baba230
+Z 01ed48a40bff392ec009867b80e6ecce

diff --git a/manifest.uuid b/manifest.uuid
index 758ca3ddc782cece74811820536825d76f1fd359..be9ae7f0eb4c18b5f444c7130cd562a616b222df 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-df5bb90d208e0633056389e97696d260e3830e8d
\ No newline at end of file
+67df44464847b43f8c0b186157e31cc66c1e5796
\ No newline at end of file

diff --git a/src/pager.c b/src/pager.c
index d8a2062282a1fcb2d2751cf434d8f7b14451a131..4cda7c92ced5b1b15648905f5756bc5abc4d6be3 100644 (file)
--- a/src/pager.c
+++ b/src/pager.c
@@ -1022,8 +1022,10 @@ static char *print_pager_state(Pager *p){
 
 /* Forward references to the various page getters */
 static int getPageNormal(Pager*,Pgno,DbPage**,int);
-static int getPageMMap(Pager*,Pgno,DbPage**,int);
 static int getPageError(Pager*,Pgno,DbPage**,int);
+#if SQLITE_MAX_MMAP_SIZE>0
+static int getPageMMap(Pager*,Pgno,DbPage**,int);
+#endif
 
 /*
 ** Set the Pager.xGet method for the appropriate routine used to fetch
@@ -1032,12 +1034,14 @@ static int getPageError(Pager*,Pgno,DbPage**,int);
 static void setGetterMethod(Pager *pPager){
   if( pPager->errCode ){
     pPager->xGet = getPageError;
+#if SQLITE_MAX_MMAP_SIZE>0
   }else if( USEFETCH(pPager)
 #ifdef SQLITE_HAS_CODEC
    && pPager->xCodec==0
 #endif
   ){
     pPager->xGet = getPageMMap;
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
   }else{
     pPager->xGet = getPageNormal;
   }
@@ -5295,10 +5299,17 @@ static void pagerUnlockIfUnused(Pager *pPager){
 }
 
 /*
-** Acquire a reference to page number pgno in pager pPager (a page
-** reference has type DbPage*). If the requested reference is 
+** The page getter methods each try to acquire a reference to a
+** page with page number pgno. If the requested reference is 
 ** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
 **
+** There are different implementations of the getter method depending
+** on the current state of the pager.
+**
+**     getPageNormal()         --  The normal getter
+**     getPageError()          --  Used if the pager is in an error state
+**     getPageMmap()           --  Used if memory-mapped I/O is enabled
+**
 ** If the requested page is already in the cache, it is returned. 
 ** Otherwise, a new page object is allocated and populated with data
 ** read from the database file. In some cases, the pcache module may
@@ -5310,14 +5321,14 @@ static void pagerUnlockIfUnused(Pager *pPager){
 ** already in the cache when this function is called, then the extra
 ** data is left as it was when the page object was last used.
 **
-** If the database image is smaller than the requested page or if a 
-** non-zero value is passed as the noContent parameter and the 
+** If the database image is smaller than the requested page or if 
+** the flags parameter contains the PAGER_GET_NOCONTENT bit and the 
 ** requested page is not already stored in the cache, then no 
 ** actual disk read occurs. In this case the memory image of the 
 ** page is initialized to all zeros. 
 **
-** If noContent is true, it means that we do not care about the contents
-** of the page. This occurs in two scenarios:
+** If PAGER_GET_NOCONTENT is true, it means that we do not care about
+** the contents of the page. This occurs in two scenarios:
 **
 **   a) When reading a free-list leaf page from the database, and
 **
@@ -5325,8 +5336,8 @@ static void pagerUnlockIfUnused(Pager *pPager){
 **      a new page into the cache to be filled with the data read
 **      from the savepoint journal.
 **
-** If noContent is true, then the data returned is zeroed instead of
-** being read from the database. Additionally, the bits corresponding
+** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead
+** of being read from the database. Additionally, the bits corresponding
 ** to pgno in Pager.pInJournal (bitvec of pages already written to the
 ** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
 ** savepoints are set. This means if the page is made writable at any
@@ -5351,9 +5362,8 @@ static int getPageNormal(
   int flags           /* PAGER_GET_XXX flags */
 ){
   int rc = SQLITE_OK;
-  PgHdr *pPg = 0;
-  u32 iFrame = 0;                 /* Frame to read from WAL file */
-  const int noContent = (flags & PAGER_GET_NOCONTENT);
+  PgHdr *pPg;
+  u8 noContent;                   /* True if PAGER_GET_NOCONTENT is set */
   sqlite3_pcache_page *pBase;
 
   if( pgno==0 ){
@@ -5367,10 +5377,10 @@ static int getPageNormal(
 
   pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
   if( pBase==0 ){
+    pPg = 0;
     rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
     if( rc!=SQLITE_OK ) goto pager_acquire_err;
     if( pBase==0 ){
-      pPg = *ppPage = 0;
       rc = SQLITE_NOMEM_BKPT;
       goto pager_acquire_err;
     }
@@ -5380,7 +5390,7 @@ static int getPageNormal(
   assert( pPg->pgno==pgno );
   assert( pPg->pPager==pPager || pPg->pPager==0 );
 
-  if( pPg->pPager && !noContent ){
+  if( pPg->pPager ){
     /* In this case the pcache already contains an initialized copy of
     ** the page. Return without further ado.  */
     assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
@@ -5401,6 +5411,7 @@ static int getPageNormal(
     }
 
     assert( !isOpen(pPager->fd) || !MEMDB );
+    noContent = (flags & PAGER_GET_NOCONTENT)!=0;
     if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){
       if( pgno>pPager->mxPgno ){
         rc = SQLITE_FULL;
@@ -5425,7 +5436,8 @@ static int getPageNormal(
       memset(pPg->pData, 0, pPager->pageSize);
       IOTRACE(("ZERO %p %d\n", pPager, pgno));
     }else{
-      if( pagerUseWal(pPager) /*&& bMmapOk==0*/ ){
+      u32 iFrame = 0;                 /* Frame to read from WAL file */
+      if( pagerUseWal(pPager) ){
         rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
         if( rc!=SQLITE_OK ) goto pager_acquire_err;
       }
@@ -5450,6 +5462,7 @@ pager_acquire_err:
   return rc;
 }
 
+#if SQLITE_MAX_MMAP_SIZE>0
 /* The page getter for when memory-mapped I/O is enabled */
 static int getPageMMap(
   Pager *pPager,      /* The pager open on the database file */
@@ -5520,6 +5533,7 @@ static int getPageMMap(
   }
   return getPageNormal(pPager, pgno, ppPage, flags);
 }
+#endif /* SQLITE_MAX_MMAP_SIZE>0 */
 
 /* The page getter method for when the pager is an error state */
 static int getPageError(