Index: src/sqlite.h.in
==================================================================
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -8295,10 +8295,22 @@
 ** of the SQL statement that triggered the call to the [xUpdate] method of the
 ** [virtual table].
 */
 int sqlite3_vtab_on_conflict(sqlite3 *);
 
+/*
+** CAPI3REF: Determine If Virtual Table Column Access Is For UPDATE
+**
+** If the sqlite3_vtab_nochange(X) routine is called within the [xColumn]
+** method of a [virtual table], then it returns true if and only if the
+** column is being fetched as part of an UPDATE operation during which the
+** column value will not change.  Applications might use this to substitute
+** a lighter-weight value to return that the corresponding [xUpdate] method
+** understands as a "no-change" value.
+*/
+int sqlite3_vtab_nochange(sqlite3_context*);
+
 /*
 ** CAPI3REF: Determine The Collation For a Virtual Table Constraint
 **
 ** This function may only be called from within a call to the [xBestIndex]
 ** method of a [virtual table]. 

Index: src/update.c
==================================================================
--- src/update.c
+++ src/update.c
@@ -825,11 +825,11 @@
   /* Populate the argument registers. */
   for(i=0; i<pTab->nCol; i++){
     if( aXRef[i]>=0 ){
       sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
     }else{
-      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
+      sqlite3VdbeAddOp4Int(v, OP_VColumn, iCsr, i, regArg+2+i, 1);
     }
   }
   if( HasRowid(pTab) ){
     sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
     if( pRowid ){

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -6691,16 +6691,22 @@
   break;
 }
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-/* Opcode: VColumn P1 P2 P3 * *
+/* Opcode: VColumn P1 P2 P3 P4 *
 ** Synopsis: r[P3]=vcolumn(P2)
 **
-** Store the value of the P2-th column of
-** the row of the virtual-table that the 
-** P1 cursor is pointing to into register P3.
+** Store in register P3 the value of the P2-th column of
+** the current row of the virtual-table of cursor P1.
+**
+** If the VColumn opcode is being used to fetch the value of
+** an unchanging column during an UPDATE operation, then the P4
+** value is 1.  Otherwise, P4 is 0.  The P4 value is returned
+** by sqlite3_vtab_nochange() routine can can be used
+** by virtual table implementations to return special "no-change"
+** marks which can be more efficient, depending on the virtual table.
 */
 case OP_VColumn: {
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
   Mem *pDest;
@@ -6718,10 +6724,11 @@
   pVtab = pCur->uc.pVCur->pVtab;
   pModule = pVtab->pModule;
   assert( pModule->xColumn );
   memset(&sContext, 0, sizeof(sContext));
   sContext.pOut = pDest;
+  sContext.bVtabNoChng = pOp->p4.i!=0;
   MemSetTypeFlag(pDest, MEM_Null);
   rc = pModule->xColumn(pCur->uc.pVCur, &sContext, pOp->p2);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( sContext.isError ){
     rc = sContext.isError;

Index: src/vdbeInt.h
==================================================================
--- src/vdbeInt.h
+++ src/vdbeInt.h
@@ -316,10 +316,11 @@
   Vdbe *pVdbe;            /* The VM that owns this context */
   int iOp;                /* Instruction number of OP_Function */
   int isError;            /* Error code returned by the function. */
   u8 skipFlag;            /* Skip accumulator loading if true */
   u8 fErrorOrAux;         /* isError!=0 or pVdbe->pAuxData modified */
+  u8 bVtabNoChng;         /* Fetching an unchanging column in a vtab UPDATE */
   u8 argc;                /* Number of arguments */
   sqlite3_value *argv[1]; /* Argument set */
 };
 
 /* A bitfield type for use inside of structures.  Always follow with :N where

Index: src/vdbeapi.c
==================================================================
--- src/vdbeapi.c
+++ src/vdbeapi.c
@@ -742,10 +742,29 @@
 */
 sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
   assert( p && p->pOut );
   return p->pOut->db;
 }
+
+/*
+** If this routine is invoked from within an xColumn method of a virtual
+** table, then it returns true if and only if the the call is during an
+** UPDATE operation and the value of the column will not be modified
+** by the UPDATE.
+**
+** If this routine is called from any context other than within the
+** xColumn method of a virtual table, then the return value is meaningless
+** and arbitrary.
+**
+** Virtual table implements might use this routine to optimize their
+** performance by substituting a NULL result, or some other light-weight
+** value, as a signal to the xUpdate routine that the column is unchanged.
+*/
+int sqlite3_vtab_nochange(sqlite3_context *p){
+  assert( p );
+  return p->bVtabNoChng;
+}
 
 /*
 ** Return the current time for a statement.  If the current time
 ** is requested more than once within the same run of a single prepared
 ** statement, the exact same time is returned for each invocation regardless