SQLite

      int addrRewind;
      int i;
      int reg;

      if( pReturning->nRetCol==0 ){
        assert( CORRUPT_DB );
      }else{
        sqlite3VdbeAddOp0(v, OP_FkCheck);
        addrRewind =
           sqlite3VdbeAddOp1(v, OP_Rewind, pReturning->iRetCur);
        VdbeCoverage(v);
        reg = pReturning->iRetReg;
        for(i=0; i<pReturning->nRetCol; i++){
          sqlite3VdbeAddOp3(v, OP_Column, pReturning->iRetCur, i, reg+i);
        }

    pTab->nTabRef++;
    if( pItem->fg.isIndexedBy && sqlite3IndexedByLookup(pParse, pItem) ){
      pTab = 0;
    }
  }
  return pTab;
}

/* Generate byte-code that will report the number of rows modified 
** by a DELETE, INSERT, or UPDATE statement.
*/
void sqlite3CodeChangeCount(Vdbe *v, int regCounter, const char *zColName){
  sqlite3VdbeAddOp0(v, OP_FkCheck);
  sqlite3VdbeAddOp2(v, OP_ResultRow, regCounter, 1);
  sqlite3VdbeSetNumCols(v, 1);
  sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zColName, SQLITE_STATIC);
}

/* Return true if table pTab is read-only.
**
** A table is read-only if any of the following are true:
**
**   1) It is a virtual table and no implementation of the xUpdate method
**      has been provided

  }

  /* Return the number of rows that were deleted. If this routine is 
  ** generating code because of a call to sqlite3NestedParse(), do not
  ** invoke the callback function.
  */
  if( memCnt ){


    sqlite3CodeChangeCount(v, memCnt, "rows deleted");
  }

delete_from_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprDelete(db, pWhere);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) 

  /*
  ** Return the number of rows inserted. If this routine is 
  ** generating code because of a call to sqlite3NestedParse(), do not
  ** invoke the callback function.
  */
  if( regRowCount ){
    sqlite3CodeChangeCount(v, regRowCount, "rows inserted");


  }

insert_cleanup:
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprListDelete(db, pList);
  sqlite3UpsertDelete(db, pUpsert);
  sqlite3SelectDelete(db, pSelect);

void sqlite3SelectDelete(sqlite3*, Select*);
Table *sqlite3SrcListLookup(Parse*, SrcList*);
int sqlite3IsReadOnly(Parse*, Table*, int);
void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
Expr *sqlite3LimitWhere(Parse*,SrcList*,Expr*,ExprList*,Expr*,char*);
#endif
void sqlite3CodeChangeCount(Vdbe*,int,const char*);
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*, ExprList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*,Expr*,int,ExprList*,Expr*,
                   Upsert*);
WhereInfo *sqlite3WhereBegin(Parse*,SrcList*,Expr*,ExprList*,ExprList*,u16,int);
void sqlite3WhereEnd(WhereInfo*);
LogEst sqlite3WhereOutputRowCount(WhereInfo*);
int sqlite3WhereIsDistinct(WhereInfo*);

  }

  /*
  ** Return the number of rows that were changed, if we are tracking
  ** that information.
  */
  if( regRowCount ){
    sqlite3CodeChangeCount(v, regRowCount, "rows updated");


  }

update_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3DbFree(db, aXRef); /* Also frees aRegIdx[] and aToOpen[] */
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprListDelete(db, pChanges);

  pIn1 = &aMem[pOp->p1];
  assert( (pIn1->flags & MEM_Int)!=0 );
  pOut = &aMem[pOp->p2];
  sqlite3VdbeMemSetInt64(pOut, pIn1->u.i);
  break;
}

/* Opcode: FkCheck * * * * *

**

** Halt with an SQLITE_CONSTRAINT error if there are any unresolved
** foreign key constraint violations.  If there are no foreign key
** constraint violations, this is a no-op.
**
** FK constraint violations are also checked when the prepared statement
** exits.  This opcode is used to raise foreign key constraint errors prior
** to returning results such as a row change count or the result of a 
** RETURNING clause.
*/
case OP_FkCheck: {

  if( (rc = sqlite3VdbeCheckFk(p,0))!=SQLITE_OK ){
    goto abort_due_to_error;
  }

  break;
}

/* Opcode: ResultRow P1 P2 * * *
** Synopsis: output=r[P1@P2]
**
** The registers P1 through P1+P2-1 contain a single row of
** results. This opcode causes the sqlite3_step() call to terminate

}

do_execsql_test 13.1 {
  INSERT INTO t1(a,b,c) VALUES(1,2,3) 
  RETURNING (SELECT b FROM t2);
} {{}}
} ;# end ifcapable rtree

# 2021-12-01 Forum post https://sqlite.org/forum/forumpost/793beaf322
# Need to report foreign key constraint errors prior to RETURNING
#
reset_db
do_execsql_test 14.0 {
  PRAGMA foreign_keys(1);
  CREATE TABLE Parent(id INTEGER PRIMARY KEY);
  CREATE TABLE Child(id INTEGER PRIMARY KEY, parent_id INTEGER REFERENCES Parent(id));
} {}
do_catchsql_test 14.1 {
  INSERT INTO child(parent_id) VALUES(123) RETURNING id;
} {1 {FOREIGN KEY constraint failed}}

finish_test