SQLite

/*
** Provide hints to the cursor.  The particular hint given (and the type
** and number of the varargs parameters) is determined by the eHintType
** parameter.  See the definitions of the BTREE_HINT_* macros for details.
*/
void sqlite3BtreeCursorHint(BtCursor *pCur, int eHintType, ...){
  /* Used only by system that substitute their own storage engine */
#ifdef SQLITE_DEBUG
  if( ALWAYS(eHintType==BTREE_HINT_RANGE) ){
    va_list ap;
    Expr *pExpr;
    Walker w;
    memset(&w, 0, sizeof(w));
    w.xExprCallback = sqlite3CursorRangeHintExprCheck;
    va_start(ap, eHintType);
    pExpr = va_arg(ap, Expr*);
    w.u.aMem = va_arg(ap, Mem*);
    va_end(ap);
    assert( pExpr!=0 );
    assert( w.u.aMem!=0 );
    sqlite3WalkExpr(&w, pExpr);
  }
#endif /* SQLITE_DEBUG */
}
#endif /* SQLITE_ENABLE_CURSOR_HINTS */


/*
** Provide flag hints to the cursor.
*/
void sqlite3BtreeCursorHintFlags(BtCursor *pCur, unsigned x){
  assert( x==BTREE_SEEK_EQ || x==BTREE_BULKLOAD || x==0 );
  pCur->hints = x;

    struct WindowRewrite *pRewrite;           /* Window rewrite context */
    struct WhereConst *pConst;                /* WHERE clause constants */
    struct RenameCtx *pRename;                /* RENAME COLUMN context */
    struct Table *pTab;                       /* Table of generated column */
    struct CoveringIndexCheck *pCovIdxCk;     /* Check for covering index */
    SrcItem *pSrcItem;                        /* A single FROM clause item */
    DbFixer *pFix;                            /* See sqlite3FixSelect() */
    Mem *aMem;                                /* See sqlite3BtreeCursorHint() */
  } u;
};

/*
** The following structure contains information used by the sqliteFix...
** routines as they walk the parse tree to make database references
** explicit.

# define sqlite3VdbeScanStatusRange(a,b,c,d)
# define sqlite3VdbeScanStatusCounters(a,b,c,d)
#endif

#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
void sqlite3VdbePrintOp(FILE*, int, VdbeOp*);
#endif

#if defined(SQLITE_ENABLE_CURSOR_HINTS) && defined(SQLITE_DEBUG)
int sqlite3CursorRangeHintExprCheck(Walker *pWalker, Expr *pExpr);
#endif

#endif /* SQLITE_VDBE_H */

                           pCtx->pFunc->zName, zContext);
    sqlite3_result_error(pCtx, zMsg, -1);
    sqlite3_free(zMsg);
    return 0;
  }
  return 1;
}

#if defined(SQLITE_ENABLE_CURSOR_HINTS) && defined(SQLITE_DEBUG)
/*
** This Walker callback is used to help verify that calls to
** sqlite3BtreeCursorHint() with opcode BTREE_HINT_RANGE have 
** byte-code register values correctly initialized.
*/
int sqlite3CursorRangeHintExprCheck(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_REGISTER ){
    assert( (pWalker->u.aMem[pExpr->iTable].flags & MEM_Undefined)==0 );
  }
  return WRC_Continue;
}
#endif /* SQLITE_ENABLE_CURSOR_HINTS && SQLITE_DEBUG */

#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Transfer error message text from an sqlite3_vtab.zErrMsg (text stored
** in memory obtained from sqlite3_malloc) into a Vdbe.zErrMsg (text stored
** in memory obtained from sqlite3DbMalloc).
*/

** Also, if the node is a TK_COLUMN that does access the table idenified
** by pCCurHint.iTabCur, and an index is being used (which we will
** know because CCurHint.pIdx!=0) then transform the TK_COLUMN into
** an access of the index rather than the original table.
*/
static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
  int rc = WRC_Continue;
  int reg;
  struct CCurHint *pHint = pWalker->u.pCCurHint;
  if( pExpr->op==TK_COLUMN ){
    if( pExpr->iTable!=pHint->iTabCur ){
      reg = ++pWalker->pParse->nMem;   /* Register for column value */
      reg = sqlite3ExprCodeTarget(pWalker->pParse, pExpr, reg);
      pExpr->op = TK_REGISTER;
      pExpr->iTable = reg;
    }else if( pHint->pIdx!=0 ){
      pExpr->iTable = pHint->iIdxCur;
      pExpr->iColumn = sqlite3TableColumnToIndex(pHint->pIdx, pExpr->iColumn);
      assert( pExpr->iColumn>=0 );
    }
  }else if( pExpr->pAggInfo ){







    rc = WRC_Prune;
    reg = ++pWalker->pParse->nMem;   /* Register for column value */
    reg = sqlite3ExprCodeTarget(pWalker->pParse, pExpr, reg);
    pExpr->op = TK_REGISTER;
    pExpr->iTable = reg;
  }
  return rc;
}

/*
** Insert an OP_CursorHint instruction if it is appropriate to do so.
*/

  CREATE VIEW   v2 AS SELECT 0 FROM v1 WHERE c1 IS '' OR c1 > '';
  CREATE VIEW   v3 AS SELECT 0 FROM v2 JOIN (v2 RIGHT JOIN v1);
  CREATE VIEW   v4 AS SELECT 0 FROM v3, v3;
  SELECT * FROM v3 JOIN v3 AS a0, v4 AS a1, v4 AS a2, v3 AS a3,
                v3 AS a4, v4 AS a5
    ORDER BY 1;
}

# 2023-04-10 https://sqlite.org/forum/forumpost/0b53708c95
#
do_execsql_test 6.0 {
  CREATE TABLE t6(a TEXT UNIQUE, b TEXT);
  INSERT INTO t6(a,b) VALUES('uvw','xyz'),('abc','def');
  WITH v1(a) AS (SELECT a COLLATE NOCASE FROM t6)
  SELECT v1.a, count(*) FROM t6 LEFT JOIN v1 ON true
   GROUP BY 1
  HAVING (SELECT true FROM t6 AS aa LEFT JOIN t6 AS bb ON length(v1.a)>5);
} {abc 2 uvw 2}

finish_test