Simplify the accessPayload() routine so that it always populates the overflow

page cache.  In the one case where populating the page cache can lead to
problems, simply invalidate the cache as soon as accessPayload() returns.
This simplification reduces code size and helps accessPayload() to run a
little faster.  This backs out the eOp==2 mode of accessPayload() added by
check-in [da59198505].

FossilOrigin-Name: 68e7a8c6765649195ef1ad9407d87d44a307b462

diff --git a/manifest b/manifest
index 1a7e283a21d7d01dc30b15aa690a13da8c6dad6e..0ab648517ffe32a0214ef132e5c00621b1e5daf5 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Remove\san\sunreachable\sbranch\sin\sthe\serror\shandling\slogic\sfor\nsqlite3BtreePayloadChecked().
-D 2017-01-26T21:30:00.788
+C Simplify\sthe\saccessPayload()\sroutine\sso\sthat\sit\salways\spopulates\sthe\soverflow\npage\scache.\s\sIn\sthe\sone\scase\swhere\spopulating\sthe\spage\scache\scan\slead\sto\s\nproblems,\ssimply\sinvalidate\sthe\scache\sas\ssoon\sas\saccessPayload()\sreturns.\s\s\nThis\ssimplification\sreduces\scode\ssize\sand\shelps\saccessPayload()\sto\srun\sa\s\nlittle\sfaster.\s\sThis\sbacks\sout\sthe\seOp==2\smode\sof\saccessPayload()\sadded\sby\s\ncheck-in\s[da59198505].
+D 2017-01-27T00:31:59.289
 F Makefile.in 5f415e7867296d678fed2e6779aea10c1318b4bc
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@ -333,7 +333,7 @@ F src/auth.c 930b376a9c56998557367e6f7f8aaeac82a2a792
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c bd72bb69abc7f3f3513308b9dd3749194b5d66d1
+F src/btree.c d42f290214e6615020b61866fe0747f02614964e
 F src/btree.h e6d352808956ec163a17f832193a3e198b3fb0ac
 F src/btreeInt.h 10c4b77c2fb399580babbcc7cf652ac10dba796e
 F src/build.c 9e799f1edd910dfa8a0bc29bd390d35d310596af
@@ -1547,7 +1547,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P b4a98f65564a0d9fba2fef95ebd00a39b3e1e572
-R 9abdd03cd61c16f0272c0fd74c72cba7
+P 293bf3ed7e40745349c83b202b27ed1b48517e1a
+R ec063431f8eb3294f488a586b69214cb
 U drh
-Z 4b9455997c313589c1136c73cb07a07d
+Z 81eb07f579988e3e7128daaaea36d064

diff --git a/manifest.uuid b/manifest.uuid
index f992289f0125cedff8031bf77216f5ab236baf42..6d62a1cc6dcfa79fd77379d040707ab4ac0151a5 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-293bf3ed7e40745349c83b202b27ed1b48517e1a
\ No newline at end of file
+68e7a8c6765649195ef1ad9407d87d44a307b462
\ No newline at end of file

diff --git a/src/btree.c b/src/btree.c
index e4a7aa160fc6ccac7d1f7c24f998d00d1f0cbe69..2575c774cf43970cacd0a984ab36769a1b9534d7 100644 (file)
--- a/src/btree.c
+++ b/src/btree.c
@@ -4424,7 +4424,6 @@ static int copyPayload(
 **
 **   0: The operation is a read. Populate the overflow cache.
 **   1: The operation is a write. Populate the overflow cache.
-**   2: The operation is a read. Do not populate the overflow cache.
 **
 ** A total of "amt" bytes are read or written beginning at "offset".
 ** Data is read to or from the buffer pBuf.
@@ -4432,13 +4431,13 @@ static int copyPayload(
 ** The content being read or written might appear on the main page
 ** or be scattered out on multiple overflow pages.
 **
-** If the current cursor entry uses one or more overflow pages and the
-** eOp argument is not 2, this function may allocate space for and lazily 
-** populates the overflow page-list cache array (BtCursor.aOverflow). 
+** If the current cursor entry uses one or more overflow pages
+** this function may allocate space for and lazily populate
+** the overflow page-list cache array (BtCursor.aOverflow). 
 ** Subsequent calls use this cache to make seeking to the supplied offset 
 ** more efficient.
 **
-** Once an overflow page-list cache has been allocated, it may be
+** Once an overflow page-list cache has been allocated, it must be
 ** invalidated if some other cursor writes to the same table, or if
 ** the cursor is moved to a different row. Additionally, in auto-vacuum
 ** mode, the following events may invalidate an overflow page-list cache.
@@ -4464,10 +4463,10 @@ static int accessPayload(
 #endif
 
   assert( pPage );
+  assert( eOp==0 || eOp==1 );
   assert( pCur->eState==CURSOR_VALID );
   assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
   assert( cursorHoldsMutex(pCur) );
-  assert( eOp!=2 || offset==0 );    /* Always start from beginning for eOp==2 */
 
   getCellInfo(pCur);
   aPayload = pCur->info.pPayload;
@@ -4489,7 +4488,7 @@ static int accessPayload(
     if( a+offset>pCur->info.nLocal ){
       a = pCur->info.nLocal - offset;
     }
-    rc = copyPayload(&aPayload[offset], pBuf, a, (eOp & 0x01), pPage->pDbPage);
+    rc = copyPayload(&aPayload[offset], pBuf, a, eOp, pPage->pDbPage);
     offset = 0;
     pBuf += a;
     amt -= a;
@@ -4505,14 +4504,13 @@ static int accessPayload(
     nextPage = get4byte(&aPayload[pCur->info.nLocal]);
 
     /* If the BtCursor.aOverflow[] has not been allocated, allocate it now.
-    ** Except, do not allocate aOverflow[] for eOp==2.
     **
     ** The aOverflow[] array is sized at one entry for each overflow page
     ** in the overflow chain. The page number of the first overflow page is
     ** stored in aOverflow[0], etc. A value of 0 in the aOverflow[] array
     ** means "not yet known" (the cache is lazily populated).
     */
-    if( eOp!=2 && (pCur->curFlags & BTCF_ValidOvfl)==0 ){
+    if( (pCur->curFlags & BTCF_ValidOvfl)==0 ){
       int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
       if( nOvfl>pCur->nOvflAlloc ){
         Pgno *aNew = (Pgno*)sqlite3Realloc(
@@ -4533,9 +4531,7 @@ static int accessPayload(
     ** entry for the first required overflow page is valid, skip
     ** directly to it.
     */
-    if( (pCur->curFlags & BTCF_ValidOvfl)!=0
-     && pCur->aOverflow[offset/ovflSize]
-    ){
+    if( pCur->aOverflow[offset/ovflSize] ){
       iIdx = (offset/ovflSize);
       nextPage = pCur->aOverflow[iIdx];
       offset = (offset%ovflSize);
@@ -4544,12 +4540,10 @@ static int accessPayload(
     assert( rc==SQLITE_OK && amt>0 );
     while( nextPage ){
       /* If required, populate the overflow page-list cache. */
-      if( (pCur->curFlags & BTCF_ValidOvfl)!=0 ){
-        assert( pCur->aOverflow[iIdx]==0
-                || pCur->aOverflow[iIdx]==nextPage
-                || CORRUPT_DB );
-        pCur->aOverflow[iIdx] = nextPage;
-      }
+      assert( pCur->aOverflow[iIdx]==0
+              || pCur->aOverflow[iIdx]==nextPage
+              || CORRUPT_DB );
+      pCur->aOverflow[iIdx] = nextPage;
 
       if( offset>=ovflSize ){
         /* The only reason to read this page is to obtain the page
@@ -4557,11 +4551,7 @@ static int accessPayload(
         ** data is not required. So first try to lookup the overflow
         ** page-list cache, if any, then fall back to the getOverflowPage()
         ** function.
-        **
-        ** Note that the aOverflow[] array must be allocated because eOp!=2
-        ** here.  If eOp==2, then offset==0 and this branch is never taken.
         */
-        assert( eOp!=2 );
         assert( pCur->curFlags & BTCF_ValidOvfl );
         assert( pCur->pBtree->db==pBt->db );
         if( pCur->aOverflow[iIdx+1] ){
@@ -4596,7 +4586,7 @@ static int accessPayload(
         ** output buffer, bypassing the page-cache altogether. This speeds
         ** up loading large records that span many overflow pages.
         */
-        if( (eOp&0x01)==0                                      /* (1) */
+        if( eOp==0                                             /* (1) */
          && offset==0                                          /* (2) */
          && pBt->inTransaction==TRANS_READ                     /* (3) */
          && (fd = sqlite3PagerFile(pBt->pPager))->pMethods     /* (4) */
@@ -4616,12 +4606,12 @@ static int accessPayload(
         {
           DbPage *pDbPage;
           rc = sqlite3PagerGet(pBt->pPager, nextPage, &pDbPage,
-              ((eOp&0x01)==0 ? PAGER_GET_READONLY : 0)
+              (eOp==0 ? PAGER_GET_READONLY : 0)
           );
           if( rc==SQLITE_OK ){
             aPayload = sqlite3PagerGetData(pDbPage);
             nextPage = get4byte(aPayload);
-            rc = copyPayload(&aPayload[offset+4], pBuf, a, (eOp&0x01), pDbPage);
+            rc = copyPayload(&aPayload[offset+4], pBuf, a, eOp, pDbPage);
             sqlite3PagerUnref(pDbPage);
             offset = 0;
           }
@@ -5253,7 +5243,8 @@ int sqlite3BtreeMovetoUnpacked(
             goto moveto_finish;
           }
           pCur->aiIdx[pCur->iPage] = (u16)idx;
-          rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 2);
+          rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0);
+          pCur->curFlags &= ~BTCF_ValidOvfl;
           if( rc ){
             sqlite3_free(pCellKey);
             goto moveto_finish;