Fix the preupdate hook so that it works when the "old.*" row has a column with a non-NULL default value that was added by ALTER TABLE ADD COLUMN after the current record was created.

FossilOrigin-Name: 00a398cf900179aa5a8aab09fe4a671d99e7a31583282848ef39390f2ef246eb

3 files changed, 30 insertions, 1 deletions

diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index 2a23c3f28..b26860f3a 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -543,6 +543,7 @@ struct PreUpdate {
   Mem *aNew;                      /* Array of new.* values */
   Table *pTab;                    /* Schema object being updated */
   Index *pPk;                     /* PK index if pTab is WITHOUT ROWID */
+  sqlite3_value **apDflt;         /* Array of default values, if required */
 };
 
 /*
diff --git a/src/vdbeapi.c b/src/vdbeapi.c
index bf185dd3a..c129b9465 100644
--- a/src/vdbeapi.c
+++ b/src/vdbeapi.c
@@ -2222,7 +2222,28 @@ int sqlite3_preupdate_old(sqlite3 *db, int iIdx, sqlite3_value **ppValue){
   if( iIdx==p->pTab->iPKey ){
     sqlite3VdbeMemSetInt64(pMem, p->iKey1);
   }else if( iIdx>=p->pUnpacked->nField ){
-    *ppValue = (sqlite3_value *)columnNullValue();
+    /* This occurs when the table has been extended using ALTER TABLE
+    ** ADD COLUMN. The value to return is the default value of the column. */
+    Column *pCol = &p->pTab->aCol[iIdx];
+    if( pCol->iDflt>0 ){
+      if( p->apDflt==0 ){
+        int nByte = sizeof(sqlite3_value*)*p->pTab->nCol;
+        p->apDflt = (sqlite3_value**)sqlite3DbMallocZero(db, nByte);
+        if( p->apDflt==0 ) goto preupdate_old_out;
+      }
+      if( p->apDflt[iIdx]==0 ){
+        Expr *pDflt = p->pTab->u.tab.pDfltList->a[pCol->iDflt-1].pExpr;
+        sqlite3_value *pVal = 0;
+        rc = sqlite3ValueFromExpr(db, pDflt, ENC(db), pCol->affinity, &pVal);
+        if( rc==SQLITE_OK && pVal==0 ){
+          rc = SQLITE_CORRUPT_BKPT;
+        }
+        p->apDflt[iIdx] = pVal;
+      }
+      *ppValue = p->apDflt[iIdx];
+    }else{
+      *ppValue = (sqlite3_value *)columnNullValue();
+    }
   }else if( p->pTab->aCol[iIdx].affinity==SQLITE_AFF_REAL ){
     if( pMem->flags & (MEM_Int|MEM_IntReal) ){
       testcase( pMem->flags & MEM_Int );
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index f1e0cccdc..a66bdecff 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -5543,5 +5543,12 @@ void sqlite3VdbePreUpdateHook(
     }
     sqlite3DbNNFreeNN(db, preupdate.aNew);
   }
+  if( preupdate.apDflt ){
+    int i;
+    for(i=0; i<pTab->nCol; i++){
+      sqlite3ValueFree(preupdate.apDflt[i]);
+    }
+    sqlite3DbFree(db, preupdate.apDflt);
+  }
 }
 #endif /* SQLITE_ENABLE_PREUPDATE_HOOK */