Further simplifications to btree.c, especially the sqlite3BtreeKey() and

sqlite3BtreeData() functions.  New assert() statements added to verify
that these routines are called correctly. (CVS 6917)

FossilOrigin-Name: 96cfd079528501f6f1e658ce8a5a4e3bdea729be

manifest

@@ -1,5 +1,5 @@
-C Change\sgetAndInitPage()\s(btree.c)\sto\suse\sonly\sPagerAcquire(),\snot\sPagerLookup()\sand\sPagerAcquire().\s(CVS\s6916)
-D 2009-07-21T19:25:24
+C Further\ssimplifications\sto\sbtree.c,\sespecially\sthe\ssqlite3BtreeKey()\sand\nsqlite3BtreeData()\sfunctions.\s\sNew\sassert()\sstatements\sadded\sto\sverify\nthat\sthese\sroutines\sare\scalled\scorrectly.\s(CVS\s6917)
+D 2009-07-22T00:35:24
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -106,8 +106,8 @@ F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c cfbf6af5b0ababb4f06ed3e75c616dadaf47fcbd
 F src/btmutex.c 0f43a75bb5b8147b386e8e1c3e71ba734e3863b7
-F src/btree.c 710f95cf3816202c64a8639677a8d9691abefa83
-F src/btree.h e53a10fd31d16c60a86f03c9467a6f470aa3683b
+F src/btree.c ece7e39b72fb42af1811c3388bbd0724fec4a664
+F src/btree.h 577448a890c2ab9b21e6ab74f073526184bceebe
 F src/btreeInt.h 1c86297e69380f6577e7ae67452597dd8d5c2705
 F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
 F src/callback.c cb68b21b0d4ae7d11ae0e487933bce3323784dcf
@@ -204,11 +204,11 @@ F src/update.c a1bbe774bce495d62dce3df3f42a5f04c1de173a
 F src/utf.c 9541d28f40441812c0b40f00334372a0542c00ff
 F src/util.c 861d5b5c58be4921f0a254489ea94cb15f550ef8
 F src/vacuum.c 3fe0eebea6d2311c1c2ab2962887d11f7a4dcfb0
-F src/vdbe.c b6fadd91f509fbcb9108f1d1a5e0985735fb315d
+F src/vdbe.c 3f4b02f59287cc65583c0bba371e9c7d047abad2
 F src/vdbe.h 35a648bc3279a120da24f34d9a25213ec15daf8a
 F src/vdbeInt.h 831c254a6eef237ef4664c8381a0137586567007
 F src/vdbeapi.c 0ab8ada7260b32031ca97f338caecf0812460624
-F src/vdbeaux.c 017bd2774528220c0c7b85342ad6b114011dfb53
+F src/vdbeaux.c a1ed07f91a9d59d39e97b2844554a07c91c9b809
 F src/vdbeblob.c a3f3e0e877fc64ea50165eec2855f5ada4477611
 F src/vdbemem.c 50cc051619ba457d762e0f17dfe1d6c926c5c4d5
 F src/vtab.c 00902f289521041712fb0293d0bf8688c7af8e48
@@ -741,7 +741,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P 716fccea58c4c217e68e04e0776e44ae39c11950
-R 1ee5a6818bfe745a7b3a3e753bd0011a
-U danielk1977
-Z 0104982a535ea93c433ad3cd1f268c89
+P 0b41dfc066b60ccabbf1a9ab4db41ebcb73a2799
+R ec7248901916ae3e3f51419c6b86f672
+U drh
+Z e29c38deeafef8c5fb9e4e32f65332cb

manifest.uuid

@@ -1 +1 @@
-0b41dfc066b60ccabbf1a9ab4db41ebcb73a2799
+96cfd079528501f6f1e658ce8a5a4e3bdea729be

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.697 2009/07/21 19:25:24 danielk1977 Exp $
+** $Id: btree.c,v 1.698 2009/07/22 00:35:24 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -539,6 +539,9 @@ static void btreeClearHasContent(BtShared *pBt){
 /*
 ** Save the current cursor position in the variables BtCursor.nKey 
 ** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
+**
+** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
+** prior to calling this routine.  
 */
 static int saveCursorPosition(BtCursor *pCur){
   int rc;
@@ -548,7 +551,7 @@ static int saveCursorPosition(BtCursor *pCur){
   assert( cursorHoldsMutex(pCur) );
 
   rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);
-  assert( rc==SQLITE_OK );  /* Cannot fail since pCur->eState==VALID */
+  assert( rc==SQLITE_OK );  /* KeySize() cannot fail */
 
   /* If this is an intKey table, then the above call to BtreeKeySize()
   ** stores the integer key in pCur->nKey. In this case this value is
@@ -2707,11 +2710,14 @@ static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
 ** database so that the last page of the file currently in use
 ** is no longer in use.
 **
-** If the nFin parameter is non-zero, the implementation assumes
+** If the nFin parameter is non-zero, this function assumes
 ** that the caller will keep calling incrVacuumStep() until
 ** it returns SQLITE_DONE or an error, and that nFin is the
 ** number of pages the database file will contain after this 
-** process is complete.
+** process is complete.  If nFin is zero, it is assumed that
+** incrVacuumStep() will be called a finite amount of times
+** which may or may not empty the freelist.  A full autovacuum
+** has nFin>0.  A "PRAGMA incremental_vacuum" has nFin==0.
 */
 static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
   Pgno nFreeList;           /* Number of pages still on the free-list */
@@ -2855,8 +2861,8 @@ static int autoVacuumCommit(BtShared *pBt){
   invalidateAllOverflowCache(pBt);
   assert(pBt->autoVacuum);
   if( !pBt->incrVacuum ){
-    Pgno nFin;         /* Number of pages to be freed */
-    Pgno nFree;        /* Number of pages no the freelist */
+    Pgno nFin;         /* Number of pages in database after autovacuuming */
+    Pgno nFree;        /* Number of pages on the freelist initially */
     Pgno nPtrmap;      /* Number of PtrMap pages to be freed */
     Pgno iFree;        /* The next page to be freed */
     int nEntry;        /* Number of entries on one ptrmap page */
@@ -3441,6 +3447,17 @@ int sqlite3BtreeCloseCursor(BtCursor *pCur){
   }
 #endif /* _MSC_VER */
 
+#ifndef NDEBUG  /* The next routine used only within assert() statements */
+/*
+** Return true if the given BtCursor is valid.  A valid cursor is one
+** that is currently pointing to a row in a (non-empty) table.
+** This is a verification routine is used only within assert() statements.
+*/
+int sqlite3BtreeCursorIsValid(BtCursor *pCur){
+  return pCur && pCur->eState==CURSOR_VALID;
+}
+#endif /* NDEBUG */
+
 /*
 ** Set *pSize to the size of the buffer needed to hold the value of
 ** the key for the current entry.  If the cursor is not pointing
@@ -3448,47 +3465,41 @@ int sqlite3BtreeCloseCursor(BtCursor *pCur){
 **
 ** For a table with the INTKEY flag set, this routine returns the key
 ** itself, not the number of bytes in the key.
+**
+** The caller must position the cursor prior to invoking this routine.
+** 
+** This routine cannot fail.  It always returns SQLITE_OK.  
 */
 int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
-  int rc;
-
   assert( cursorHoldsMutex(pCur) );
-  rc = restoreCursorPosition(pCur);
-  if( rc==SQLITE_OK ){
   assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
-    if( pCur->eState==CURSOR_INVALID ){
+  if( pCur->eState!=CURSOR_VALID ){
     *pSize = 0;
   }else{
     getCellInfo(pCur);
     *pSize = pCur->info.nKey;
   }
-  }
-  return rc;
+  return SQLITE_OK;
 }
 
 /*
 ** Set *pSize to the number of bytes of data in the entry the
-** cursor currently points to.  Always return SQLITE_OK.
-** Failure is not possible.  If the cursor is not currently
-** pointing to an entry (which can happen, for example, if
-** the database is empty) then *pSize is set to 0.
+** cursor currently points to.
+**
+** The caller must guarantee that the cursor is pointing to a non-NULL
+** valid entry.  In other words, the calling procedure must guarantee
+** that the cursor has Cursor.eState==CURSOR_VALID.
+**
+** Failure is not possible.  This function always returns SQLITE_OK.
+** It might just as well be a procedure (returning void) but we continue
+** to return an integer result code for historical reasons.
 */
 int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
-  int rc;
-
   assert( cursorHoldsMutex(pCur) );
-  rc = restoreCursorPosition(pCur);
-  if( rc==SQLITE_OK ){
-    assert( pCur->eState==CURSOR_INVALID || pCur->eState==CURSOR_VALID );
-    if( pCur->eState==CURSOR_INVALID ){
-      /* Not pointing at a valid entry - set *pSize to 0. */
-      *pSize = 0;
-    }else{
+  assert( pCur->eState==CURSOR_VALID );
   getCellInfo(pCur);
   *pSize = pCur->info.nData;
-    }
-  }
-  return rc;
+  return SQLITE_OK;
 }
 
 /*

src/btree.h

@@ -13,7 +13,7 @@
 ** subsystem.  See comments in the source code for a detailed description
 ** of what each interface routine does.
 **
-** @(#) $Id: btree.h,v 1.119 2009/07/09 05:07:38 danielk1977 Exp $
+** @(#) $Id: btree.h,v 1.120 2009/07/22 00:35:24 drh Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -185,6 +185,10 @@ int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
 void sqlite3BtreeCacheOverflow(BtCursor *);
 void sqlite3BtreeClearCursor(BtCursor *);
 
+#ifndef NDEBUG
+int sqlite3BtreeCursorIsValid(BtCursor*);
+#endif
+
 #ifndef SQLITE_OMIT_BTREECOUNT
 int sqlite3BtreeCount(BtCursor *, i64 *);
 #endif

src/vdbe.c

@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.872 2009/07/14 18:35:45 drh Exp $
+** $Id: vdbe.c,v 1.873 2009/07/22 00:35:24 drh Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -2055,6 +2055,7 @@ case OP_Column: {
       payloadSize = pC->payloadSize;
       zRec = (char*)pC->aRow;
     }else if( pC->isIndex ){
+      assert( sqlite3BtreeCursorIsValid(pCrsr) );
       rc = sqlite3BtreeKeySize(pCrsr, &payloadSize64);
       assert( rc==SQLITE_OK );   /* True because of CursorMoveto() call above */
       /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
@@ -2063,8 +2064,9 @@ case OP_Column: {
       assert( (payloadSize64 & SQLITE_MAX_U32)==(u64)payloadSize64 );
       payloadSize = (u32)payloadSize64;
     }else{
+      assert( sqlite3BtreeCursorIsValid(pCrsr) );
       rc = sqlite3BtreeDataSize(pCrsr, &payloadSize);
-      assert( rc==SQLITE_OK );   /* True because of CursorMoveto() call above */
+      assert( rc==SQLITE_OK );   /* DataSize() cannot fail */
     }
   }else if( pC->pseudoTable ){
     /* The record is the sole entry of a pseudo-table */
@@ -3593,6 +3595,7 @@ case OP_NewRowid: {           /* out2-prerelease */
         if( res ){
           v = 1;
         }else{
+          assert( sqlite3BtreeCursorIsValid(pC->pCursor) );
           rc = sqlite3BtreeKeySize(pC->pCursor, &v);
           assert( rc==SQLITE_OK );   /* Cannot fail following BtreeLast() */
           if( v==MAX_ROWID ){
@@ -3879,6 +3882,7 @@ case OP_RowData: {
   assert( pC->pseudoTable==0 );
   assert( pC->pCursor!=0 );
   pCrsr = pC->pCursor;
+  assert( sqlite3BtreeCursorIsValid(pCrsr) );
 
   /* The OP_RowKey and OP_RowData opcodes always follow OP_NotExists or
   ** OP_Rewind/Op_Next with no intervening instructions that might invalidate
@@ -3899,7 +3903,7 @@ case OP_RowData: {
     n = (u32)n64;
   }else{
     rc = sqlite3BtreeDataSize(pCrsr, &n);
-    assert( rc==SQLITE_OK );    /* True because of CursorMoveto() call above */
+    assert( rc==SQLITE_OK );    /* DataSize() cannot fail */
     if( n>(u32)db->aLimit[SQLITE_LIMIT_LENGTH] ){
       goto too_big;
     }

src/vdbeaux.c

@@ -14,7 +14,7 @@
 ** to version 2.8.7, all this code was combined into the vdbe.c source file.
 ** But that file was getting too big so this subroutines were split out.
 **
-** $Id: vdbeaux.c,v 1.476 2009/07/17 17:25:43 danielk1977 Exp $
+** $Id: vdbeaux.c,v 1.477 2009/07/22 00:35:24 drh Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -2599,6 +2599,7 @@ int sqlite3VdbeIdxRowid(sqlite3 *db, BtCursor *pCur, i64 *rowid){
   ** Any corruption is detected in sqlite3BtreeParseCellPtr(), though, so
   ** this code can safely assume that nCellKey is 32-bits  
   */
+  assert( sqlite3BtreeCursorIsValid(pCur) );
   rc = sqlite3BtreeKeySize(pCur, &nCellKey);
   assert( rc==SQLITE_OK );     /* pCur is always valid so KeySize cannot fail */
   assert( (nCellKey & SQLITE_MAX_U32)==(u64)nCellKey );
@@ -2675,6 +2676,7 @@ int sqlite3VdbeIdxKeyCompare(
   BtCursor *pCur = pC->pCursor;
   Mem m;
 
+  assert( sqlite3BtreeCursorIsValid(pCur) );
   rc = sqlite3BtreeKeySize(pCur, &nCellKey);
   assert( rc==SQLITE_OK );    /* pCur is always valid so KeySize cannot fail */
   /* nCellKey will always be between 0 and 0xffffffff because of the say