In UPDATE processing, include generated columns in the set of columns being

updated if and only if their generator expressions reference some other
column that is being updated.

FossilOrigin-Name: d38176e93a628e03f1bd8b689fbc4152a1495388da917c2d89cefed04353d2d6

2 files changed, 36 insertions, 2 deletions

diff --git a/src/build.c b/src/build.c
index 2ba939822..efdcb59b1 100644
--- a/src/build.c
+++ b/src/build.c
@@ -1405,6 +1405,12 @@ void sqlite3AddDefaultValue(
     if( !sqlite3ExprIsConstantOrFunction(pExpr, db->init.busy) ){
       sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
           pCol->zName);
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+    }else if( pCol->colFlags & COLFLAG_GENERATED ){
+      testcase( pCol->colflags & COLFLAG_VIRTUAL );
+      testcase( pCol->colflags & COLFLAG_STORED );
+      sqlite3ErrorMsg(pParse, "cannot use DEFAULT on a generated column");
+#endif
     }else{
       /* A copy of pExpr is used instead of the original, as pExpr contains
       ** tokens that point to volatile memory.
@@ -1633,14 +1639,14 @@ void sqlite3AddGenerated(Parse *pParse, Expr *pExpr, Token *pType){
   goto generated_done;
 
 generated_error:
-  sqlite3ErrorMsg(pParse, "incorrect GENERATED ALWAYS AS on column \"%s\"",
+  sqlite3ErrorMsg(pParse, "error in generated column \"%s\"",
                   pCol->zName);
 generated_done:
   sqlite3ExprDelete(pParse->db, pExpr);
 #else
   /* Throw and error for the GENERATED ALWAYS AS clause if the
   ** SQLITE_OMIT_GENERATED_COLUMNS compile-time option is used. */
-  sqlite3ErrorMsg(pParse, "GENERATED ALWAYS AS not supported");
+  sqlite3ErrorMsg(pParse, "generated columns not supported");
   sqlite3ExprDelete(pParse->db, pExpr);
 #endif
 }
diff --git a/src/update.c b/src/update.c
index 48413a0df..d690b69f9 100644
--- a/src/update.c
+++ b/src/update.c
@@ -356,6 +356,33 @@ void sqlite3Update(
   assert( chngPk==0 || chngPk==1 );
   chngKey = chngRowid + chngPk;
 
+#ifndef SQLITE_OMIT_GENERATED_COLUMNS
+  /* Mark generated columns as changing if their generator expressions
+  ** reference any changing column.  The actual aXRef[] value for 
+  ** generated expressions is not used, other than to check to see that it
+  ** is non-negative, so the value of aXRef[] for generated columns can be
+  ** set to any non-negative number.  We use 99999 so that the value is
+  ** obvious when looking at aXRef[] in a symbolic debugger. 
+  */
+  if( pTab->tabFlags & TF_HasGenerated ){
+    int bProgress;
+    testcase( pTab->tabFlags & TF_HasVirtual );
+    testcase( pTab->tabFlags & TF_HasStored );
+    do{
+      bProgress = 0;
+      for(i=0; i<pTab->nCol; i++){
+        if( aXRef[i]>=0 ) continue;
+        if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 ) continue;
+        if( sqlite3ExprReferencesUpdatedColumn(pTab->aCol[i].pDflt,
+                                               aXRef, chngRowid) ){
+          aXRef[i] = 99999;
+          bProgress = 1;
+        }
+      }
+    }while( bProgress );
+  }
+#endif
+
   /* The SET expressions are not actually used inside the WHERE loop.  
   ** So reset the colUsed mask. Unless this is a virtual table. In that
   ** case, set all bits of the colUsed mask (to ensure that the virtual
@@ -952,6 +979,7 @@ static void updateVirtualTable(
 
   /* Populate the argument registers. */
   for(i=0; i<pTab->nCol; i++){
+    assert( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 );
     if( aXRef[i]>=0 ){
       sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
     }else{