Another fix to [e33da6d5dc964db8]: Ensure that the EXISTS-to-JOIN break

happens even if the inner loop is a "no-op" loop that never executes more
than once because it is controlled by a UNIQUE index.  This resolves the
error reported in [forum:/forumpost/7992838ba2|forum post 7992838ba2].
Test cases are in TH3.

FossilOrigin-Name: bbded6477020af4d52253c5af2d33ec9b9cd619d33f744206f7420458bd84f12

manifest

@@ -1,5 +1,5 @@
-C Update\sthe\sautoconf\sMakefile.msc\sbased\son\sthe\sMakefile.msc\schanges\sin\sthe\nprevious\scheck-in.
-D 2025-12-05T00:56:51.025
+C Another\sfix\sto\s[e33da6d5dc964db8]:\sEnsure\sthat\sthe\sEXISTS-to-JOIN\sbreak\nhappens\seven\sif\sthe\sinner\sloop\sis\sa\s"no-op"\sloop\sthat\snever\sexecutes\smore\nthan\sonce\sbecause\sit\sis\scontrolled\sby\sa\sUNIQUE\sindex.\s\sThis\sresolves\sthe\nerror\sreported\sin\s[forum:/forumpost/7992838ba2|forum\spost\s7992838ba2].\nTest\scases\sare\sin\sTH3.
+D 2025-12-05T01:33:23.992
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -818,7 +818,7 @@ F src/vxworks.h 9d18819c5235b49c2340a8a4d48195ec5d5afb637b152406de95a9436beeaeab
 F src/wal.c 505a98fbc599a971d92cb90371cf54546c404cd61e04fd093e7b0c8ff978f9b6
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
-F src/where.c 1b554a868134cbc9ca2192385403c0b63e5073ff01a6cdd600a846c09f843165
+F src/where.c 287324fe73a0ae8e55b3be89bb2fe4148e3a8394e1e2f10ed2113713a037d8a3
 F src/whereInt.h 8d94cb116c9e06205c3d5ac87af065fc044f8cf08bfdccd94b6ea1c1308e65da
 F src/wherecode.c 71c5c6804b7f882dec8ec858758accae02fcfca13df3cc720f1f258e663ec7c5
 F src/whereexpr.c 5f412da6616e26b8000dd736a5ce5da0018dff0933cd656bbb25f407db16bf93
@@ -2184,8 +2184,8 @@ F tool/version-info.c 33d0390ef484b3b1cb685d59362be891ea162123cea181cb8e6d2cf6dd
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh d924598cf2f55a4ecbc2aeb055c10bd5f48114793e7ba25f9585435da29e7e98
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 0b75057d61ccd57fca19d49679f0ff99231595f619aa0c4310aa3180b8de08b7
-R 495edf45a012303eb9f0a754fea978ad
+P 8dce36698949f2e3a9948afc7c2b6c06f575d12033148e8c55fa79c03a73e2b4
+R 2440a17c53adf3cd06510dbc8328e330
 U drh
-Z 45c171a27a0a33e83f25884aef748799
+Z c606aa1c85654749574896aa57a1c98a
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-8dce36698949f2e3a9948afc7c2b6c06f575d12033148e8c55fa79c03a73e2b4
+bbded6477020af4d52253c5af2d33ec9b9cd619d33f744206f7420458bd84f12

src/where.c

@@ -7380,6 +7380,9 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
   sqlite3 *db = pParse->db;
   int iEnd = sqlite3VdbeCurrentAddr(v);
   int nRJ = 0;
+#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
+  int addrSeek = 0;
+#endif
 
   /* Generate loop termination code.
   */
@@ -7392,7 +7395,10 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
       ** the RIGHT JOIN table */
       WhereRightJoin *pRJ = pLevel->pRJ;
       sqlite3VdbeResolveLabel(v, pLevel->addrCont);
-      pLevel->addrCont = 0;
+      /* Replace addrCont with a new label that will never be used, just so
+      ** the subsequent call to resolve pLevel->addrCont will have something
+      ** to resolve. */
+      pLevel->addrCont = sqlite3VdbeMakeLabel(pParse);
       pRJ->endSubrtn = sqlite3VdbeCurrentAddr(v);
       sqlite3VdbeAddOp3(v, OP_Return, pRJ->regReturn, pRJ->addrSubrtn, 1);
       VdbeCoverage(v);
@@ -7401,7 +7407,6 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
     pLoop = pLevel->pWLoop;
     if( pLevel->op!=OP_Noop ){
 #ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
-      int addrSeek = 0;
       Index *pIdx;
       int n;
       if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
@@ -7424,25 +7429,26 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
         sqlite3VdbeAddOp2(v, OP_Goto, 1, pLevel->p2);
       }
 #endif /* SQLITE_DISABLE_SKIPAHEAD_DISTINCT */
-      if( pTabList->a[pLevel->iFrom].fg.fromExists && i==pWInfo->nLevel-1 ){
-        /* If the EXISTS-to-JOIN optimization was applied, then the EXISTS
-        ** loop(s) will be the inner-most loops of the join. There might be
-        ** multiple EXISTS loops, but they will all be nested, and the join
-        ** order will not have been changed by the query planner.  If the
-        ** inner-most EXISTS loop sees a single successful row, it should
-        ** break out of *all* EXISTS loops.  But only the inner-most of the
-        ** nested EXISTS loops should do this breakout. */
-        int nOuter = 0; /* Nr of outer EXISTS that this one is nested within */
-        while( nOuter<i ){
-          if( !pTabList->a[pLevel[-nOuter-1].iFrom].fg.fromExists ) break;
-          nOuter++;
-        }
-        testcase( nOuter>0 );
-        sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel[-nOuter].addrBrk);
-        VdbeComment((v, "EXISTS break"));
+    }
+    if( pTabList->a[pLevel->iFrom].fg.fromExists && i==pWInfo->nLevel-1 ){
+      /* If the EXISTS-to-JOIN optimization was applied, then the EXISTS
+      ** loop(s) will be the inner-most loops of the join. There might be
+      ** multiple EXISTS loops, but they will all be nested, and the join
+      ** order will not have been changed by the query planner.  If the
+      ** inner-most EXISTS loop sees a single successful row, it should
+      ** break out of *all* EXISTS loops.  But only the inner-most of the
+      ** nested EXISTS loops should do this breakout. */
+      int nOuter = 0; /* Nr of outer EXISTS that this one is nested within */
+      while( nOuter<i ){
+        if( !pTabList->a[pLevel[-nOuter-1].iFrom].fg.fromExists ) break;
+        nOuter++;
       }
-      /* The common case: Advance to the next row */
-      if( pLevel->addrCont ) sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+      testcase( nOuter>0 );
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel[-nOuter].addrBrk);
+      VdbeComment((v, "EXISTS break"));
+    }
+    sqlite3VdbeResolveLabel(v, pLevel->addrCont);
+    if( pLevel->op!=OP_Noop ){
       sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
       sqlite3VdbeChangeP5(v, pLevel->p5);
       VdbeCoverage(v);
@@ -7455,10 +7461,11 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
         VdbeCoverage(v);
       }
 #ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
-      if( addrSeek ) sqlite3VdbeJumpHere(v, addrSeek);
+      if( addrSeek ){
+        sqlite3VdbeJumpHere(v, addrSeek);
+        addrSeek = 0;
+      }
 #endif
-    }else if( pLevel->addrCont ){
-      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
     }
     if( (pLoop->wsFlags & WHERE_IN_ABLE)!=0 && pLevel->u.in.nIn>0 ){
       struct InLoop *pIn;