From d8c0ba3b02aa16e9f248db1acc6a233eef62cc4e Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Tue, 30 Jun 2015 03:57:59 +0000
Subject: [PATCH] Optimization to the sqlite3PcacheFetch() logic.

FossilOrigin-Name: d9a0481ce0fd9824b1566f182d68ec46ef091b1b
---
 manifest      | 14 +++++++-------
 manifest.uuid |  2 +-
 src/pager.c   |  6 ++++++
 src/pcache.c  |  4 ++--
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/manifest b/manifest
index 4773cc0264..6a222cd1bf 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Put\sall\svariable\sdeclarations\sfor\ssqlite3PagerWrite()\nat\sthe\sbeginning\sof\sthe\sblock.\s\sSyntax\sonly\s-\sno\slogic\schanges.
-D 2015-06-30T03:34:13.376
+C Optimization\sto\sthe\ssqlite3PcacheFetch()\slogic.
+D 2015-06-30T03:57:59.045
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 285a0a234ed7610d431d91671c136098c2bd86a9
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -314,10 +314,10 @@ F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
 F src/os_unix.c 23eb5f56fac54d8fe0cb204291f3b3b2d94f23fc
 F src/os_win.c 27cc135e2d0b8b1e2e4944db1e2669a6a18fa0f8
 F src/os_win.h eb7a47aa17b26b77eb97e4823f20a00b8bda12ca
-F src/pager.c fbd0dd63da21d62c51e845b919548d6eb14dd2ff
+F src/pager.c 3fa869dafdb59ece9d318177e3b9972039dfee39
 F src/pager.h c3476e7c89cdf1c6914e50a11f3714e30b4e0a77
 F src/parse.y 6d60dda8f8d418b6dc034f1fbccd816c459983a8
-F src/pcache.c 379fd77feb732b39750eb733260d9c227d8a4314
+F src/pcache.c cde06aa50962595e412d497e22fd2e07878ba1f0
 F src/pcache.h 9968603796240cdf83da7e7bef76edf90619cea9
 F src/pcache1.c 9ec20f98f50ed7415019303ae9bd3745d4b7bd9b
 F src/pragma.c c1f4d012ea9f6b1ce52d341b2cd0ad72d560afd7
@@ -1364,7 +1364,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 8001aa52bd12f900092387fe3571463e89efd977
-R 3ab730a0fd8ce3dab29c0f5735db472f
+P a0fa6b3ba59716e53b8c035b497602050ed0ccb8
+R ef96145c17347794d738ef415b1d0f04
 U drh
-Z 2e2284bbdb4fcaa6c0dd63e70a1d9358
+Z a3fb1d60e02fc08f324c2aa0fa9d650d
diff --git a/manifest.uuid b/manifest.uuid
index c6fb62560a..caf2e1d807 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-a0fa6b3ba59716e53b8c035b497602050ed0ccb8
\ No newline at end of file
+d9a0481ce0fd9824b1566f182d68ec46ef091b1b
\ No newline at end of file
diff --git a/src/pager.c b/src/pager.c
index dd3cac40a1..0ac05f715b 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -5312,6 +5312,11 @@ int sqlite3PagerAcquire(
       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;
+          goto pager_acquire_err;
+        }
       }
       pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
       if( pPg==0 ) rc = SQLITE_NOMEM;
@@ -5418,6 +5423,7 @@ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
   assert( pPager->pPCache!=0 );
   pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
   assert( pPage==0 || pPager->hasBeenUsed );
+  if( pPage==0 ) return 0;
   return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
 }
 
diff --git a/src/pcache.c b/src/pcache.c
index 9b23bd8433..58c05ac2a4 100644
--- a/src/pcache.c
+++ b/src/pcache.c
@@ -321,7 +321,7 @@ static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
   assert( pPage!=0 );
   pPgHdr = (PgHdr*)pPage->pExtra;
   assert( pPgHdr->pPage==0 );
- memset(pPgHdr, 0, sizeof(PgHdr));
+  memset(pPgHdr, 0, sizeof(PgHdr));
   pPgHdr->pPage = pPage;
   pPgHdr->pData = pPage->pBuf;
   pPgHdr->pExtra = (void *)&pPgHdr[1];
@@ -345,7 +345,7 @@ PgHdr *sqlite3PcacheFetchFinish(
 ){
   PgHdr *pPgHdr;
 
-  if( pPage==0 ) return 0;
+  assert( pPage!=0 );
   pPgHdr = (PgHdr *)pPage->pExtra;
 
   if( !pPgHdr->pPage ){