From: drh <drh@noemail.net>
Date: Tue, 13 Dec 2016 14:32:47 +0000 (+0000)
Subject: Make the sqlite3PagerGet() interface into a virtual method, with different
X-Git-Tag: version-3.16.0~48^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=12e6f682798853ab44a08ee4fd203d11d9899b47;p=thirdparty%2Fsqlite.git

Make the sqlite3PagerGet() interface into a virtual method, with different
implementations based on the current state of the pager.  This gives a small
performance increase by avoiding unnecessary branches inside the various
methods.

FossilOrigin-Name: df5bb90d208e0633056389e97696d260e3830e8d
---

diff --git a/manifest b/manifest
index 4a681af0fe..8e294defe8 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sthe\s--mmap\soption\sto\sthe\sspeedtest1\sprogram\sand\sto\sthe\sspeed-check.sh\nscript\sthat\sis\sfrequently\sused\sto\srun\sspeedtest1.
-D 2016-12-12T23:24:08.261
+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
 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 eaf8590131ab651420e86e89c3fd12d729f55ad3
+F src/pager.c e99f7edfab2441f55fc1a4f4dd05f3bf0f1a82cd
 F src/pager.h d1e944291030351f362a0a7da9b5c3e34e603e39
 F src/parse.y 29153738a7322054359320eb00b5a4cd44389f20
 F src/pcache.c 219fc5238d5c80e2990ab01e1459db3a96866447
@@ -1536,7 +1536,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 1b36fbb9f05f3a5844e198b489bff36ef6cd908c
-R 54a6c1795de20385060d3d26915836b2
+P 1a636d5e0eec0a4d968519d1dfd35a983e512c78
+R d5446ab8495308acac3b07699664fa42
+T *branch * pager-get-method
+T *sym-pager-get-method *
+T -sym-trunk *
 U drh
-Z 47f248a7928b3840fe2e23a9066d59e9
+Z 3a0d20f1bb36125dcd9d753c0baba230
diff --git a/manifest.uuid b/manifest.uuid
index 1f2e52b085..758ca3ddc7 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-1a636d5e0eec0a4d968519d1dfd35a983e512c78
\ No newline at end of file
+df5bb90d208e0633056389e97696d260e3830e8d
\ No newline at end of file
diff --git a/src/pager.c b/src/pager.c
index 02e9aac790..d8a2062282 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -693,6 +693,7 @@ struct Pager {
   int nRead;                  /* Database pages read */
 #endif
   void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
+  int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */
 #ifdef SQLITE_HAS_CODEC
   void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
   void (*xCodecSizeChng)(void*,int,int); /* Notify of page size changes */
@@ -1019,6 +1020,29 @@ static char *print_pager_state(Pager *p){
 }
 #endif
 
+/* 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);
+
+/*
+** Set the Pager.xGet method for the appropriate routine used to fetch
+** content from the pager.
+*/
+static void setGetterMethod(Pager *pPager){
+  if( pPager->errCode ){
+    pPager->xGet = getPageError;
+  }else if( USEFETCH(pPager)
+#ifdef SQLITE_HAS_CODEC
+   && pPager->xCodec==0
+#endif
+  ){
+    pPager->xGet = getPageMMap;
+  }else{
+    pPager->xGet = getPageNormal;
+  }
+}
+
 /*
 ** Return true if it is necessary to write page *pPg into the sub-journal.
 ** A page needs to be written into the sub-journal if there exists one
@@ -1833,6 +1857,7 @@ static void pager_unlock(Pager *pPager){
     }
     if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
     pPager->errCode = SQLITE_OK;
+    setGetterMethod(pPager);
   }
 
   pPager->journalOff = 0;
@@ -1870,6 +1895,7 @@ static int pager_error(Pager *pPager, int rc){
   if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
     pPager->errCode = rc;
     pPager->eState = PAGER_ERROR;
+    setGetterMethod(pPager);
   }
   return rc;
 }
@@ -3437,6 +3463,7 @@ static void pagerFixMaplimit(Pager *pPager){
     sqlite3_int64 sz;
     sz = pPager->szMmap;
     pPager->bUseFetch = (sz>0);
+    setGetterMethod(pPager);
     sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
   }
 #endif
@@ -4854,6 +4881,7 @@ act_like_temp_file:
   /* pPager->xBusyHandler = 0; */
   /* pPager->pBusyHandlerArg = 0; */
   pPager->xReiniter = xReinit;
+  setGetterMethod(pPager);
   /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
   /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
 
@@ -5316,7 +5344,7 @@ static void pagerUnlockIfUnused(Pager *pPager){
 ** Since Lookup() never goes to disk, it never has to deal with locks
 ** or journal files.
 */
-int sqlite3PagerGet(
+static int getPageNormal(
   Pager *pPager,      /* The pager open on the database file */
   Pgno pgno,          /* Page number to fetch */
   DbPage **ppPage,    /* Write a pointer to the page here */
@@ -5326,92 +5354,28 @@ int sqlite3PagerGet(
   PgHdr *pPg = 0;
   u32 iFrame = 0;                 /* Frame to read from WAL file */
   const int noContent = (flags & PAGER_GET_NOCONTENT);
+  sqlite3_pcache_page *pBase;
 
-  /* It is acceptable to use a read-only (mmap) page for any page except
-  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
-  ** flag was specified by the caller. And so long as the db is not a 
-  ** temporary or in-memory database.  */
-  const int bMmapOk = (pgno>1 && USEFETCH(pPager)
-   && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
-#ifdef SQLITE_HAS_CODEC
-   && pPager->xCodec==0
-#endif
-  );
-
-  /* Optimization note:  Adding the "pgno<=1" term before "pgno==0" here
-  ** allows the compiler optimizer to reuse the results of the "pgno>1"
-  ** test in the previous statement, and avoid testing pgno==0 in the
-  ** common case where pgno is large. */
-  if( pgno<=1 && pgno==0 ){
+  if( pgno==0 ){
     return SQLITE_CORRUPT_BKPT;
   }
+  assert( pPager->errCode==SQLITE_OK );
   assert( pPager->eState>=PAGER_READER );
   assert( assert_pager_state(pPager) );
-  assert( noContent==0 || bMmapOk==0 );
-
   assert( pPager->hasHeldSharedLock==1 );
 
-  /* If the pager is in the error state, return an error immediately. 
-  ** Otherwise, request the page from the PCache layer. */
-  if( pPager->errCode!=SQLITE_OK ){
-    rc = pPager->errCode;
-  }else{
-    if( bMmapOk && pagerUseWal(pPager) ){
-      rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-      if( rc!=SQLITE_OK ) goto pager_acquire_err;
-    }
-
-    if( bMmapOk && iFrame==0 ){
-      void *pData = 0;
-
-      rc = sqlite3OsFetch(pPager->fd, 
-          (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
-      );
-
-      if( rc==SQLITE_OK && pData ){
-        if( pPager->eState>PAGER_READER || pPager->tempFile ){
-          pPg = sqlite3PagerLookup(pPager, pgno);
-        }
-        if( pPg==0 ){
-          rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
-        }else{
-          sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
-        }
-        if( pPg ){
-          assert( rc==SQLITE_OK );
-          *ppPage = pPg;
-          return SQLITE_OK;
-        }
-      }
-      if( rc!=SQLITE_OK ){
-        goto pager_acquire_err;
-      }
-    }
 
-    {
-      sqlite3_pcache_page *pBase;
-      pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
-      if( pBase==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;
-        }
-      }
-      pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
-      assert( pPg!=0 );
+  pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
+  if( pBase==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;
     }
   }
-
-  if( rc!=SQLITE_OK ){
-    /* Either the call to sqlite3PcacheFetch() returned an error or the
-    ** pager was already in the error-state when this function was called.
-    ** Set pPg to 0 and jump to the exception handler.  */
-    pPg = 0;
-    goto pager_acquire_err;
-  }
+  pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
   assert( pPg==(*ppPage) );
   assert( pPg->pgno==pgno );
   assert( pPg->pPager==pPager || pPg->pPager==0 );
@@ -5461,7 +5425,7 @@ int sqlite3PagerGet(
       memset(pPg->pData, 0, pPager->pageSize);
       IOTRACE(("ZERO %p %d\n", pPager, pgno));
     }else{
-      if( pagerUseWal(pPager) && bMmapOk==0 ){
+      if( pagerUseWal(pPager) /*&& bMmapOk==0*/ ){
         rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
         if( rc!=SQLITE_OK ) goto pager_acquire_err;
       }
@@ -5474,7 +5438,6 @@ int sqlite3PagerGet(
     }
     pager_set_pagehash(pPg);
   }
-
   return SQLITE_OK;
 
 pager_acquire_err:
@@ -5483,11 +5446,105 @@ pager_acquire_err:
     sqlite3PcacheDrop(pPg);
   }
   pagerUnlockIfUnused(pPager);
-
   *ppPage = 0;
   return rc;
 }
 
+/* The page getter for when memory-mapped I/O is enabled */
+static int getPageMMap(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  int rc = SQLITE_OK;
+  PgHdr *pPg = 0;
+  u32 iFrame = 0;                 /* Frame to read from WAL file */
+
+  assert( USEFETCH(pPager) );
+#ifdef SQLITE_HAS_CODEC
+  assert( pPager->xCodec==0 );
+#endif
+
+  /* It is acceptable to use a read-only (mmap) page for any page except
+  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
+  ** flag was specified by the caller. And so long as the db is not a 
+  ** temporary or in-memory database.  */
+  const int bMmapOk = (pgno>1
+   && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
+  );
+
+  /* Optimization note:  Adding the "pgno<=1" term before "pgno==0" here
+  ** allows the compiler optimizer to reuse the results of the "pgno>1"
+  ** test in the previous statement, and avoid testing pgno==0 in the
+  ** common case where pgno is large. */
+  if( pgno<=1 && pgno==0 ){
+    return SQLITE_CORRUPT_BKPT;
+  }
+  assert( pPager->eState>=PAGER_READER );
+  assert( assert_pager_state(pPager) );
+  assert( pPager->hasHeldSharedLock==1 );
+  assert( pPager->errCode==SQLITE_OK );
+
+  if( bMmapOk && pagerUseWal(pPager) ){
+    rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
+    if( rc!=SQLITE_OK ){
+      *ppPage = 0;
+      return rc;
+    }
+  }
+  if( bMmapOk && iFrame==0 ){
+    void *pData = 0;
+    rc = sqlite3OsFetch(pPager->fd, 
+        (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
+    );
+    if( rc==SQLITE_OK && pData ){
+      if( pPager->eState>PAGER_READER || pPager->tempFile ){
+        pPg = sqlite3PagerLookup(pPager, pgno);
+      }
+      if( pPg==0 ){
+        rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
+     }else{
+        sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
+      }
+      if( pPg ){
+        assert( rc==SQLITE_OK );
+        *ppPage = pPg;
+        return SQLITE_OK;
+      }
+    }
+    if( rc!=SQLITE_OK ){
+      *ppPage = 0;
+      return rc;
+    }
+  }
+  return getPageNormal(pPager, pgno, ppPage, flags);
+}
+
+/* The page getter method for when the pager is an error state */
+static int getPageError(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  assert( pPager->errCode!=SQLITE_OK );
+  *ppPage = 0;
+  return pPager->errCode;
+}
+
+
+/* Dispatch all page fetch requests to the appropriate getter method.
+*/
+int sqlite3PagerGet(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  return pPager->xGet(pPager, pgno, ppPage, flags);
+}
+
 /*
 ** Acquire a page if it is already in the in-memory cache.  Do
 ** not read the page from disk.  Return a pointer to the page,
@@ -6460,6 +6517,7 @@ int sqlite3PagerRollback(Pager *pPager){
       */
       pPager->errCode = SQLITE_ABORT;
       pPager->eState = PAGER_ERROR;
+      setGetterMethod(pPager);
       return rc;
     }
   }else{
@@ -6721,6 +6779,7 @@ int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
     ){
       pPager->errCode = SQLITE_ABORT;
       pPager->eState = PAGER_ERROR;
+      setGettterMethod(pPager);
     }
 #endif
   }
@@ -6793,6 +6852,7 @@ void sqlite3PagerSetCodec(
   pPager->xCodecSizeChng = xCodecSizeChng;
   pPager->xCodecFree = xCodecFree;
   pPager->pCodec = pCodec;
+  setGetterMethod(pPager);
   pagerReportSize(pPager);
 }
 void *sqlite3PagerGetCodec(Pager *pPager){