Fix a problem with using streaming iterators with sqlite3changegroup_add_change().

FossilOrigin-Name: 3dbde727146d28c316df47c7b5116be7f2476a0a0c893207c2a4ca3ab285cb5e

ext/session/sessionchange.test

@@ -96,6 +96,22 @@ do_test 1.5 {
 $iter finalize
 grp delete
 
+do_test 1.6 { 
+  set C [changeset_from_sql {
+    INSERT INTO t1 VALUES(1001, hex(randomblob(10000)), hex(randomblob(10000)));
+    INSERT INTO t1 VALUES(2001, hex(randomblob(10000)), hex(randomblob(10000)));
+    INSERT INTO t1 VALUES(3001, hex(randomblob(10000)), hex(randomblob(10000)));
+  }]
+
+  sqlite3changegroup grp
+  set iter [sqlite3changeset_start $C]
+  while {[$iter next]=="SQLITE_ROW"} {
+    grp add_change $iter
+  }
+  $iter finalize
+} SQLITE_OK
+
+grp delete
 
 
 finish_test

ext/session/sqlite3session.c

@@ -3396,14 +3396,15 @@ int sqlite3changeset_start_v2_strm(
 ** object and the buffer is full, discard some data to free up space.
 */
 static void sessionDiscardData(SessionInput *pIn){
-  if( pIn->xInput && pIn->iNext>=sessions_strm_chunk_size ){
-    int nMove = pIn->buf.nBuf - pIn->iNext;
+  if( pIn->xInput && pIn->iCurrent>=sessions_strm_chunk_size ){
+    int nMove = pIn->buf.nBuf - pIn->iCurrent;
     assert( nMove>=0 );
     if( nMove>0 ){
-      memmove(pIn->buf.aBuf, &pIn->buf.aBuf[pIn->iNext], nMove);
+      memmove(pIn->buf.aBuf, &pIn->buf.aBuf[pIn->iCurrent], nMove);
     }
-    pIn->buf.nBuf -= pIn->iNext;
-    pIn->iNext = 0;
+    pIn->buf.nBuf -= pIn->iCurrent;
+    pIn->iNext -= pIn->iCurrent;
+    pIn->iCurrent = 0;
     pIn->nData = pIn->buf.nBuf;
   }
 }
@@ -3757,8 +3758,8 @@ static int sessionChangesetNextOne(
   p->rc = sessionInputBuffer(&p->in, 2);
   if( p->rc!=SQLITE_OK ) return p->rc;
 
-  sessionDiscardData(&p->in);
   p->in.iCurrent = p->in.iNext;
+  sessionDiscardData(&p->in);
 
   /* If the iterator is already at the end of the changeset, return DONE. */
   if( p->in.iNext>=p->in.nData ){
@@ -6117,14 +6118,19 @@ int sqlite3changegroup_add_change(
   sqlite3_changegroup *pGrp,
   sqlite3_changeset_iter *pIter
 ){
+  int rc = SQLITE_OK;
+
   if( pIter->in.iCurrent==pIter->in.iNext 
    || pIter->rc!=SQLITE_OK 
    || pIter->bInvert
   ){
     /* Iterator does not point to any valid entry or is an INVERT iterator. */
-    return SQLITE_ERROR;
+    rc = SQLITE_ERROR;
+  }else{
+    pIter->in.bNoDiscard = 1;
+    rc = sessionOneChangeToHash(pGrp, pIter, 0);
   }
-  return sessionOneChangeToHash(pGrp, pIter, 0);
+  return rc;
 }
 
 /*

ext/session/test_session.c

@@ -1459,6 +1459,9 @@ struct TestChangegroup {
 typedef struct TestChangeIter TestChangeIter;
 struct TestChangeIter {
   sqlite3_changeset_iter *pIter;
+
+  /* If this iter uses streaming. */
+  TestStreamInput in;
 };
 
 
@@ -1681,6 +1684,7 @@ static int SQLITE_TCLAPI test_sqlite3changeset_start(
   sqlite3_changeset_iter *pIter = 0;
   int flags = 0;
   int rc = SQLITE_OK;
+  int nAlloc = 0;                 /* Bytes of space to allocate */
 
   static int iCmd = 1;
   char zCmd[64];
@@ -1696,18 +1700,36 @@ static int SQLITE_TCLAPI test_sqlite3changeset_start(
     return TCL_ERROR;
   }
 
-  flags = isInvert ? SQLITE_CHANGESETSTART_INVERT : 0;
   pChangeset = (void *)Tcl_GetByteArrayFromObj(objv[objc-1], &nChangeset);
-  rc = sqlite3changeset_start_v2(&pIter, (int)nChangeset, pChangeset, flags);
+  flags = isInvert ? SQLITE_CHANGESETSTART_INVERT : 0;
+
+  nAlloc = sizeof(TestChangeIter);
+  if( test_tcl_integer(interp, SESSION_STREAM_TCL_VAR) ){
+    nAlloc += nChangeset;
+  }
+  pNew = (TestChangeIter*)ckalloc(nAlloc);
+  memset(pNew, 0, nAlloc);
+  if( test_tcl_integer(interp, SESSION_STREAM_TCL_VAR) ){
+    pNew->in.nStream = test_tcl_integer(interp, SESSION_STREAM_TCL_VAR);
+    pNew->in.nData = nChangeset;
+    pNew->in.aData = (unsigned char*)&pNew[1];
+    memcpy(pNew->in.aData, pChangeset, nChangeset);
+  }
+
+  if( pNew->in.nStream ){
+    void *pCtx = (void*)&pNew->in;
+    rc = sqlite3changeset_start_v2_strm(&pIter, testStreamInput, pCtx, flags);
+  }else{
+    rc = sqlite3changeset_start_v2(&pIter, (int)nChangeset, pChangeset, flags);
+  }
   if( rc!=SQLITE_OK ){
     char *zErr = sqlite3_mprintf(
         "error in sqlite3changeset_start_v2() - %d", rc
     );
     Tcl_AppendResult(interp, zErr, (char*)0);
+    ckfree(pNew);
     return TCL_ERROR;
   }
-
-  pNew = (TestChangeIter*)ckalloc(sizeof(TestChangeIter));
   pNew->pIter = pIter;
 
   sprintf(zCmd, "csiter%d", iCmd++);

manifest

@@ -1,5 +1,5 @@
-C Clarify\ssome\smalloc\ssize\scomputations\sto\ssimplify\sthe\sproof\sthat\sthey\nare\ssafe.\s\sRemove\ssome\scode\sassociated\swith\scygwin\sthat\sis\smarked\s"#if\s0".
-D 2025-05-19T14:50:36.906
+C Fix\sa\sproblem\swith\susing\sstreaming\siterators\swith\ssqlite3changegroup_add_change().
+D 2025-05-22T18:04:48.757
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -601,7 +601,7 @@ F ext/session/sessionalter.test e852acb3d2357aac7d0b920a2109da758c4331bfdf85b41d
 F ext/session/sessionat.test 00c8badb35e43a2f12a716d2734a44d614ff62361979b6b85419035bc04b45ee
 F ext/session/sessionbig.test 47c381e7acfabeef17d98519a3080d69151723354d220afa2053852182ca7adf
 F ext/session/sessionblob.test 87faf667870b72f08e91969abd9f52a383ab7b514506ee194d64a39d8faff00a
-F ext/session/sessionchange.test 77c4702050f24270b58070e2cf01c95c3d232a3ef164b70f31974b386ce69903
+F ext/session/sessionchange.test 6618cb1c1338a4b6df173b6ac42d09623fb71269962abf23ebb7617fe9f45a50
 F ext/session/sessionconflict.test 19e4a53795c4c930bfec49e809311e09b2a9e202d9446e56d7a8b139046a0c07 x
 F ext/session/sessiondiff.test e89f7aedcdd89e5ebac3a455224eb553a171e9586fc3e1e6a7b3388d2648ba8d
 F ext/session/sessionfault.test c2b43d01213b389a3f518e90775fca2120812ba51e50444c4066962263e45c11
@@ -617,9 +617,9 @@ F ext/session/sessionrowid.test 85187c2f1b38861a5844868126f69f9ec62223a03449a98a
 F ext/session/sessionsize.test 8fcf4685993c3dbaa46a24183940ab9f5aa9ed0d23e5fb63bfffbdb56134b795
 F ext/session/sessionstat1.test 5e718d5888c0c49bbb33a7a4f816366db85f59f6a4f97544a806421b85dc2dec
 F ext/session/sessionwor.test 6fd9a2256442cebde5b2284936ae9e0d54bde692d0f5fd009ecef8511f4cf3fc
-F ext/session/sqlite3session.c 7a8816d56940c464c74706dfb02f18129b290655df1ccb8648228a7d436141f2
+F ext/session/sqlite3session.c 6b0877fe1ab832aa4b85eaca72606dfd1630a1363a1be7af10ee1042a5ec719e
 F ext/session/sqlite3session.h 9bb1a6687b467764b35178dc29bbd2c57ab8cd3acdc8a62f088c34ad17e4fe2b
-F ext/session/test_session.c af162108e8dc40cb9fe0e876e0155cecabcb49e82e5939677d21451e36160283
+F ext/session/test_session.c 2ddff73ea368d827028c32851b291416e1008845832feb27b751d15e57e13cc3
 F ext/wasm/EXPORTED_FUNCTIONS.fiddle.in 27450c8b8c70875a260aca55435ec927068b34cef801a96205adb81bdcefc65c
 F ext/wasm/GNUmakefile 24d7e6f446528fa67f5ade6c3c7d7e46e1ac52649d6264cbe24539c1dab608e1
 F ext/wasm/README-dist.txt f01081a850ce38a56706af6b481e3a7878e24e42b314cfcd4b129f0f8427066a
@@ -2207,8 +2207,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 1ad0169b022b280bcaaf94a7fa231591be96b514230ab5c98fbf15cd7df842dd
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 8819b7285b71932327f47d29fa575cfb338e2fccd3f7c2023faf0575bfdb0079
-R 946ad68930588fd8088439cf4ef3fb55
-U drh
-Z 28d57a56afcfa879aa70c91fd7351c46
+P ba8184d132a935aa1980fbfb61ff308b93d433d559db4968f9014f7653ac9c6e
+R 6545703450e23e51a4d8ba6cf71d201b
+U dan
+Z e2a99740785b40c0ced82e554792c0ed
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-ba8184d132a935aa1980fbfb61ff308b93d433d559db4968f9014f7653ac9c6e
+3dbde727146d28c316df47c7b5116be7f2476a0a0c893207c2a4ca3ab285cb5e