Remove the unused PGHDR_NEED_READ flag. Add invariant checking (during

SQLITE_DEBUG builds only) for the PgHdr object.

FossilOrigin-Name: 771c5411e9ebcad00fb4b97556b519488284b87b

manifest

@@ -1,5 +1,5 @@
-C Clarification\sof\sthe\spagerFlushOnCommit()\slogic.
+C Remove\sthe\sunused\sPGHDR_NEED_READ\sflag.\s\sAdd\sinvariant\schecking\s(during\nSQLITE_DEBUG\sbuilds\sonly)\sfor\sthe\sPgHdr\sobject.
-D 2016-05-13T12:12:38.291
+D 2016-05-13T15:22:06.587
 F Makefile.in 9eda6e1c90d05c199c3ec8a7069b0682ad307657
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc db82b35aef27f412fef14d8534afc022138bcdfd
@@ -364,11 +364,11 @@ F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
 F src/os_unix.c a9443cdab41d7f3cdf0df3a5aab62fd6e1c9b234
 F src/os_win.c 852fc2ff6084296348ed3739c548b2cf32df394e
 F src/os_win.h eb7a47aa17b26b77eb97e4823f20a00b8bda12ca
-F src/pager.c 665c5a4da55952ac144c29d83e7f24393ce80dce
+F src/pager.c 3910579bfbe323dfabed2b95d201159b61b8ef42
 F src/pager.h 329bdf078a4e0a3b35084534d58625d21fd03681
 F src/parse.y 10eb2f3fb62341291528c7984498054731f9d31e
-F src/pcache.c ad5ce697dc5a734caddb2b1eac83b195da95ddbe
+F src/pcache.c e93f1e1b4c6134d59b4bd4f3f684f406987ef299
-F src/pcache.h 33b40350df1b6c278e019dee37f87e1bac276223
+F src/pcache.h 2cedcd8407eb23017d92790b112186886e179490
 F src/pcache1.c 7f51d2b541aab57596adf62db2c4bb025d34f04d
 F src/pragma.c faf42922bb7ab2f6672cb550356c1967abae3c84
 F src/pragma.h 64c78a648751b9f4f297276c4eb7507b14b4628c
@@ -1488,7 +1488,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9495d33879221c1821331dc72c61a6a3d182f526
+P 3401d9dcdbec390564574e8d2972c944c204e025
-R 6b2058239dcedcc73d7ba7314be4d002
+R 440a1b1b52d8bc83687d285c09ed1eae
 U drh
-Z 481738e778b68e5e24387a60a8825df4
+Z 63614a0e4a8fa1151ab9567f8bbeafca

manifest.uuid

@@ -1 +1 @@
-3401d9dcdbec390564574e8d2972c944c204e025
+771c5411e9ebcad00fb4b97556b519488284b87b

src/pager.c

@@ -2377,7 +2377,6 @@ static int pager_playback_one_page(
     assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
     pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
     if( rc!=SQLITE_OK ) return rc;
-    pPg->flags &= ~PGHDR_NEED_READ;
     sqlite3PcacheMakeDirty(pPg);
   }
   if( pPg ){
@@ -6005,6 +6004,7 @@ void sqlite3PagerDontWrite(PgHdr *pPg){
     IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
     pPg->flags |= PGHDR_DONT_WRITE;
     pPg->flags &= ~PGHDR_WRITEABLE;
+    testcase( pPg->flags & PGHDR_NEED_SYNC );
     pager_set_pagehash(pPg);
   }
 }

src/pcache.c

@@ -53,11 +53,18 @@ struct PCache {
   sqlite3_pcache *pCache;             /* Pluggable cache module */
 };
 
+/********************************** Test and Debug Logic **********************/
 /*
-** Debug tracing macros
+** Debug tracing macros.  Enable by by changing the "0" to "1" and
+** recompiling.
+**
+** When sqlite3PcacheTrace is 1, single line trace messages are issued.
+** When sqlite3PcacheTrace is 2, a dump of the pcache showing all cache entries
+** is displayed for many operations, resulting in a lot of output.
 */
 #if defined(SQLITE_DEBUG) && 0
-  int sqlite3PcacheTrace = 2;
+  int sqlite3PcacheTrace = 2;       /* 0: off  1: simple  2: cache dumps */
+  int sqlite3PcacheMxDump = 9999;   /* Max cache entries for pcacheDump() */
 # define pcacheTrace(X) if(sqlite3PcacheTrace){sqlite3DebugPrintf X;}
   void pcacheDump(PCache *pCache){
     int N;
@@ -69,7 +76,7 @@ struct PCache {
     if( sqlite3PcacheTrace<2 ) return;
     if( pCache->pCache==0 ) return;
     N = sqlite3PcachePagecount(pCache);
-    if( N>5 ) N = 5;
+    if( N>sqlite3PcacheMxDump ) N = sqlite3PcacheMxDump;
     for(i=1; i<=N; i++){
        pLower = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, i, 0);
        if( pLower==0 ) continue;
@@ -88,6 +95,46 @@ struct PCache {
 # define pcacheDump(X)
 #endif
 
+/*
+** Check invariants on a PgHdr entry.  Return true if everything is OK.
+** Return false if any invariant is violated.
+**
+** This routine is for use inside of assert() statements only.  For
+** example:
+**
+**          assert( sqlite3PcachePageSanity(pPg) );
+*/
+#if SQLITE_DEBUG
+int sqlite3PcachePageSanity(PgHdr *pPg){
+  PCache *pCache;
+  assert( pPg!=0 );
+  assert( pPg->pgno>0 );    /* Page number is 1 or more */
+  pCache = pPg->pCache;
+  assert( pCache!=0 );      /* Every page has an associated PCache */
+  if( pPg->flags & PGHDR_CLEAN ){
+    assert( (pPg->flags & PGHDR_DIRTY)==0 );/* Cannot be both CLEAN and DIRTY */
+    assert( pCache->pDirty!=pPg );          /* CLEAN pages not on dirty list */
+    assert( pCache->pDirtyTail!=pPg );
+  }
+  /* WRITEABLE pages must also be DIRTY */
+  if( pPg->flags & PGHDR_WRITEABLE ){
+    assert( pPg->flags & PGHDR_DIRTY );     /* WRITEABLE implies DIRTY */
+  }
+  /* NEED_SYNC can be set independently of WRITEABLE.  This can happen,
+  ** for example, when using the sqlite3PagerDontWrite() optimization:
+  **    (1)  Page X is journalled, and gets WRITEABLE and NEED_SEEK.
+  **    (2)  Page X moved to freelist, WRITEABLE is cleared
+  **    (3)  Page X reused, WRITEABLE is set again
+  ** If NEED_SYNC had been cleared in step 2, then it would not be reset
+  ** in step 3, and page might be written into the database without first
+  ** syncing the rollback journal, which might cause corruption on a power
+  ** loss.
+  */
+  return 1;
+}
+#endif /* SQLITE_DEBUG */
+
+
 /********************************** Linked List Management ********************/
 
 /* Allowed values for second argument to pcacheManageDirtyList() */
@@ -439,6 +486,7 @@ PgHdr *sqlite3PcacheFetchFinish(
   }
   pCache->nRefSum++;
   pPgHdr->nRef++;
+  assert( sqlite3PcachePageSanity(pPgHdr) );
   return pPgHdr;
 }
 
@@ -467,6 +515,7 @@ void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
 */
 void sqlite3PcacheRef(PgHdr *p){
   assert(p->nRef>0);
+  assert( sqlite3PcachePageSanity(p) );
   p->nRef++;
   p->pCache->nRefSum++;
 }
@@ -478,6 +527,7 @@ void sqlite3PcacheRef(PgHdr *p){
 */
 void sqlite3PcacheDrop(PgHdr *p){
   assert( p->nRef==1 );
+  assert( sqlite3PcachePageSanity(p) );
   if( p->flags&PGHDR_DIRTY ){
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
   }
@@ -491,6 +541,7 @@ void sqlite3PcacheDrop(PgHdr *p){
 */
 void sqlite3PcacheMakeDirty(PgHdr *p){
   assert( p->nRef>0 );
+  assert( sqlite3PcachePageSanity(p) );
   if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){    /*OPTIMIZATION-IF-FALSE*/
     p->flags &= ~PGHDR_DONT_WRITE;
     if( p->flags & PGHDR_CLEAN ){
@@ -499,6 +550,7 @@ void sqlite3PcacheMakeDirty(PgHdr *p){
       assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY );
       pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
     }
+    assert( sqlite3PcachePageSanity(p) );
   }
 }
 
@@ -507,12 +559,14 @@ void sqlite3PcacheMakeDirty(PgHdr *p){
 ** make it so.
 */
 void sqlite3PcacheMakeClean(PgHdr *p){
+  assert( sqlite3PcachePageSanity(p) );
   if( ALWAYS((p->flags & PGHDR_DIRTY)!=0) ){
     assert( (p->flags & PGHDR_CLEAN)==0 );
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
     p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
     p->flags |= PGHDR_CLEAN;
     pcacheTrace(("%p.CLEAN %d\n",p->pCache,p->pgno));
+    assert( sqlite3PcachePageSanity(p) );
     if( p->nRef==0 ){
       pcacheUnpin(p);
     }
@@ -560,6 +614,7 @@ void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
   PCache *pCache = p->pCache;
   assert( p->nRef>0 );
   assert( newPgno>0 );
+  assert( sqlite3PcachePageSanity(p) );
   pcacheTrace(("%p.MOVE %d -> %d\n",pCache,p->pgno,newPgno));
   sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);
   p->pgno = newPgno;

src/pcache.h

@@ -51,11 +51,10 @@ struct PgHdr {
 #define PGHDR_WRITEABLE       0x004  /* Journaled and ready to modify */
 #define PGHDR_NEED_SYNC       0x008  /* Fsync the rollback journal before
                                      ** writing this page to the database */
-#define PGHDR_NEED_READ       0x010  /* Content is unread */
+#define PGHDR_DONT_WRITE      0x010  /* Do not write content to disk */
-#define PGHDR_DONT_WRITE      0x020  /* Do not write content to disk */
+#define PGHDR_MMAP            0x020  /* This is an mmap page object */
-#define PGHDR_MMAP            0x040  /* This is an mmap page object */
 
-#define PGHDR_WAL_APPEND      0x080  /* Appended to wal file */
+#define PGHDR_WAL_APPEND      0x040  /* Appended to wal file */
 
 /* Initialize and shutdown the page cache subsystem */
 int sqlite3PcacheInitialize(void);
@@ -138,6 +137,11 @@ int sqlite3PcachePagecount(PCache*);
 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
 #endif
 
+#if defined(SQLITE_DEBUG)
+/* Check invariants on a PgHdr object */
+int sqlite3PcachePageSanity(PgHdr*);
+#endif
+
 /* Set and get the suggested cache-size for the specified pager-cache.
 **
 ** If no global maximum is configured, then the system attempts to limit