Index: src/upsert.c
==================================================================
--- src/upsert.c
+++ src/upsert.c
@@ -224,10 +224,11 @@
       for(i=0; i<nPk; i++){
         int k;
         assert( pPk->aiColumn[i]>=0 );
         k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[i]);
         sqlite3VdbeAddOp3(v, OP_Column, iCur, k, iPk+i);
+        VdbeComment((v, "%s.%s", pIdx->zName, pTab->aCol[i].zName));
       }
       i = sqlite3VdbeAddOp4Int(v, OP_Found, iDataCur, 0, iPk, nPk);
       VdbeCoverage(v);
       sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_CORRUPT, OE_Abort);
       sqlite3VdbeJumpHere(v, i);