Add the new sqlite3PagerUnrefPageOne() pager method to deal with the special

case of unreferencing page1.

FossilOrigin-Name: b2e2100cf766da1cb499aec0ca0a9969d7af5d93312ab8cf895fbf4a6ffb9b2f

diff --git a/manifest b/manifest
index 082580d908241f901621fc327136c5ef19603493..633c8bc7120f81e0b3df13b1d0f603bfa254255d 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Remove\san\sobsolete\soptimization\sin\spcache\sthat\sdue\sto\smore\srecent\schanges\nwas\srecently\smaking\sthe\scode\sa\slittle\sslower.
-D 2017-09-01T12:57:33.041
+C Add\sthe\snew\ssqlite3PagerUnrefPageOne()\spager\smethod\sto\sdeal\swith\sthe\sspecial\ncase\sof\sunreferencing\spage1.
+D 2017-09-01T14:50:19.167
 F Makefile.in c644bbe8ebe4aae82ad6783eae6b6beea4c727b99ff97568b847ced5e2ac7afb
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 25b154da7f0b3d4924f27378c1f8d006285b80811f1ccf3ed953dbebf6282136
@@ -399,7 +399,7 @@ F src/auth.c 6277d63837357549fe14e723490d6dc1a38768d71c795c5eb5c0f8a99f918f73
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c 1033b88fe50aba7d364b5a19666a9a274caa8d4c25ab7f3914221997b46af44a
+F src/btree.c f1ac9509f4595d034fe432982c39d51ac2bfc9bd83136d16255aede35c526b45
 F src/btree.h 32ef5d3f25dc70ef1ee9cecf84a023c21378f06a57cd701d2e866e141b150f09
 F src/btreeInt.h 55b702efce17e5d1941865464227d3802cfc9c7c832fac81d4c94dced47a71fc
 F src/build.c e71e96a67daf3d1dd23188423e66cd6af38017e2ec73fead5d2b57da2d3c7e16
@@ -443,8 +443,8 @@ F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
 F src/os_unix.c 489aa972ccc34f7b4770b891694b32101c59ddd4be4ef0ddd9a4da58c145c1a6
 F src/os_win.c 964165b66cde03abc72fe948198b01be608436894732eadb94c8720d2467f223
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c bf51378c57c8e05d7f4d7bb9861f403a2e40cde82e25513401216d1ed30bc3e5
-F src/pager.h f2a99646c5533ffe11afa43e9e0bea74054e4efa
+F src/pager.c 3936b32a0a45f1b80462b38ba1ed0556e62843554a089ab9c4be1a35c97f23bc
+F src/pager.h 581698f2177e8bd4008fe4760898ce20b6133d1df22139b9101b5155f900df7a
 F src/parse.y 52ef3cecd0934e9da4a45b585883a03243ad615d338ad94f44501a05891dcdfa
 F src/pcache.c 4bada070456980c3c1f16d58ec2e64e389ad77b935e3d77e0c96e7bbd397289c
 F src/pcache.h 072f94d29281cffd99e46c1539849f248c4b56ae7684c1f36626797fee375170
@@ -1651,7 +1651,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 919863b14859d958d6c078097faae02070c7bd082e2814cf3f84bd84921e4419
-R 0eee553fc228f3f42e4580f46005e756
+P c4e7e175eecfd79015f4fae99618dfce6baf97c21bf3c909ea535d4e12dcaaad
+R 6f9a52521f107a3c330b7cfcb23523cf
 U drh
-Z 71c472332c9be0857de95ba6da186b34
+Z f39368718f6b0d67941da00fc11a34d5

diff --git a/manifest.uuid b/manifest.uuid
index e4cecf80a42b9113e06b71a41cefbe8a40c059c4..1aa72acac969237b711e508827db105737ba8022 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-c4e7e175eecfd79015f4fae99618dfce6baf97c21bf3c909ea535d4e12dcaaad
\ No newline at end of file
+b2e2100cf766da1cb499aec0ca0a9969d7af5d93312ab8cf895fbf4a6ffb9b2f
\ No newline at end of file

diff --git a/src/btree.c b/src/btree.c
index 9ec61507cbf9ae388dcb16e7408e7e062b3958bf..3ca0037e9dd4cd2cd2153ff4738eea4ba8bdc697 100644 (file)
--- a/src/btree.c
+++ b/src/btree.c
@@ -439,7 +439,8 @@ static void downgradeAllSharedCacheTableLocks(Btree *p){
 
 #endif /* SQLITE_OMIT_SHARED_CACHE */
 
-static void releasePage(MemPage *pPage);
+static void releasePage(MemPage *pPage);         /* Forward reference */
+static void releasePageOne(MemPage *pPage);      /* Forward reference */
 static void releasePageNotNull(MemPage *pPage);  /* Forward reference */
 
 /*
@@ -2109,6 +2110,8 @@ getAndInitPage_error:
 /*
 ** Release a MemPage.  This should be called once for each prior
 ** call to btreeGetPage.
+**
+** Page1 is a special case and must be released using releasePageOne().
 */
 static void releasePageNotNull(MemPage *pPage){
   assert( pPage->aData );
@@ -2122,6 +2125,16 @@ static void releasePageNotNull(MemPage *pPage){
 static void releasePage(MemPage *pPage){
   if( pPage ) releasePageNotNull(pPage);
 }
+static void releasePageOne(MemPage *pPage){
+  assert( pPage!=0 );
+  assert( pPage->aData );
+  assert( pPage->pBt );
+  assert( pPage->pDbPage!=0 );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  sqlite3PagerUnrefPageOne(pPage->pDbPage);
+}
 
 /*
 ** Get an unused page.
@@ -3000,7 +3013,7 @@ static int lockBtree(BtShared *pBt){
       }else{
         setDefaultSyncFlag(pBt, SQLITE_DEFAULT_WAL_SYNCHRONOUS+1);
         if( isOpen==0 ){
-          releasePage(pPage1);
+          releasePageOne(pPage1);
           return SQLITE_OK;
         }
       }
@@ -3047,7 +3060,7 @@ static int lockBtree(BtShared *pBt){
       ** zero and return SQLITE_OK. The caller will call this function
       ** again with the correct page-size.
       */
-      releasePage(pPage1);
+      releasePageOne(pPage1);
       pBt->usableSize = usableSize;
       pBt->pageSize = pageSize;
       freeTempSpace(pBt);
@@ -3101,7 +3114,7 @@ static int lockBtree(BtShared *pBt){
   return SQLITE_OK;
 
 page1_init_failed:
-  releasePage(pPage1);
+  releasePageOne(pPage1);
   pBt->pPage1 = 0;
   return rc;
 }
@@ -3146,7 +3159,7 @@ static void unlockBtreeIfUnused(BtShared *pBt){
     assert( pPage1->aData );
     assert( sqlite3PagerRefcount(pBt->pPager)==1 );
     pBt->pPage1 = 0;
-    releasePageNotNull(pPage1);
+    releasePageOne(pPage1);
   }
 }
 
@@ -4068,7 +4081,7 @@ int sqlite3BtreeRollback(Btree *p, int tripCode, int writeOnly){
       if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
       testcase( pBt->nPage!=nPage );
       pBt->nPage = nPage;
-      releasePage(pPage1);
+      releasePageOne(pPage1);
     }
     assert( countValidCursors(pBt, 1)==0 );
     pBt->inTransaction = TRANS_READ;

diff --git a/src/pager.c b/src/pager.c
index 2e5977fe43e7b741ba2301276bd824edce0d21db..b3ec03bd952a07f0a674cf81424b83ffc4f78efa 100644 (file)
--- a/src/pager.c
+++ b/src/pager.c
@@ -5350,7 +5350,8 @@ int sqlite3PagerSharedLock(Pager *pPager){
 ** nothing to rollback, so this routine is a no-op.
 */ 
 static void pagerUnlockIfUnused(Pager *pPager){
-  if( pPager->nMmapOut==0 && (sqlite3PcacheRefCount(pPager->pPCache)==0) ){
+  if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){
+    assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */
     pagerUnlockAndRollback(pPager);
   }
 }
@@ -5636,25 +5637,39 @@ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
 /*
 ** Release a page reference.
 **
-** If the number of references to the page drop to zero, then the
-** page is added to the LRU list.  When all references to all pages
-** are released, a rollback occurs and the lock on the database is
-** removed.
+** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be
+** used if we know that the page being released is not the last page.
+** The btree layer always holds page1 open until the end, so these first
+** to routines can be used to release any page other than BtShared.pPage1.
+**
+** Use sqlite3PagerUnrefPageOne() to release page1.  This latter routine
+** checks the total number of outstanding pages and if the number of
+** pages reaches zero it drops the database lock.
 */
 void sqlite3PagerUnrefNotNull(DbPage *pPg){
-  Pager *pPager;
+  TESTONLY( Pager *pPager = pPg->pPager; )
   assert( pPg!=0 );
-  pPager = pPg->pPager;
   if( pPg->flags & PGHDR_MMAP ){
+    assert( pPg->pgno!=1 );  /* Page1 is never memory mapped */
     pagerReleaseMapPage(pPg);
   }else{
     sqlite3PcacheRelease(pPg);
   }
-  pagerUnlockIfUnused(pPager);
+  /* Do not use this routine to release the last reference to page1 */
+  assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
 }
 void sqlite3PagerUnref(DbPage *pPg){
   if( pPg ) sqlite3PagerUnrefNotNull(pPg);
 }
+void sqlite3PagerUnrefPageOne(DbPage *pPg){
+  Pager *pPager;
+  assert( pPg!=0 );
+  assert( pPg->pgno==1 );
+  assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */
+  pPager = pPg->pPager;
+  sqlite3PcacheRelease(pPg);
+  pagerUnlockIfUnused(pPager);
+}
 
 /*
 ** This function is called at the start of every write transaction.

diff --git a/src/pager.h b/src/pager.h
index 585ef2949794f910fdd15dcbb966b292147fa12a..126267bcc80f0703bf913b71536cb6557bb71baa 100644 (file)
--- a/src/pager.h
+++ b/src/pager.h
@@ -151,6 +151,7 @@ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno);
 void sqlite3PagerRef(DbPage*);
 void sqlite3PagerUnref(DbPage*);
 void sqlite3PagerUnrefNotNull(DbPage*);
+void sqlite3PagerUnrefPageOne(DbPage*);
 
 /* Operations on page references. */
 int sqlite3PagerWrite(DbPage*);