SQLite

    Window *pNext = p->pNextWin;
    sqlite3WindowDelete(db, p);
    p = pNext;
  }
}

/*
** The argument expression is an PRECEDING or FOLLOWING offset.  The
** value should be a non-negative integer.  If the value is not a
** constant, change it to NULL.  The fact that it is then a non-negative
** integer will be caught later.  But it is important not to leave
** variable values in the expression tree.
*/
static Expr *sqlite3WindowOffsetExpr(Parse *pParse, Expr *pExpr){
  if( 0==sqlite3ExprIsConstant(pExpr) ){
    sqlite3ExprDelete(pParse->db, pExpr);
    pExpr = sqlite3ExprAlloc(pParse->db, TK_NULL, 0, 0);
  }
  return pExpr;
}

/*
** Allocate and return a new Window object describing a Window Definition.
*/
Window *sqlite3WindowAlloc(
  Parse *pParse,    /* Parsing context */
  int eType,        /* Frame type. TK_RANGE or TK_ROWS */
  int eStart,       /* Start type: CURRENT, PRECEDING, FOLLOWING, UNBOUNDED */
  Expr *pStart,     /* Start window size if TK_PRECEDING or FOLLOWING */
  int eEnd,         /* End type: CURRENT, FOLLOWING, TK_UNBOUNDED, PRECEDING */
  Expr *pEnd        /* End window size if TK_FOLLOWING or PRECEDING */
){
  Window *pWin = 0;

  /* Parser assures the following: */
  assert( eType==TK_RANGE || eType==TK_ROWS );
  assert( eStart==TK_CURRENT || eStart==TK_PRECEDING
           || eStart==TK_UNBOUNDED || eStart==TK_FOLLOWING );
  assert( eEnd==TK_CURRENT || eEnd==TK_FOLLOWING
           || eEnd==TK_UNBOUNDED || eEnd==TK_PRECEDING );
  assert( (eStart==TK_PRECEDING || eStart==TK_FOLLOWING)==(pStart!=0) );
  assert( (eEnd==TK_FOLLOWING || eEnd==TK_PRECEDING)==(pEnd!=0) );


  /* If a frame is declared "RANGE" (not "ROWS"), then it may not use
  ** either "<expr> PRECEDING" or "<expr> FOLLOWING".
  */
  if( eType==TK_RANGE && (pStart!=0 || pEnd!=0) ){
    sqlite3ErrorMsg(pParse, "RANGE must use only UNBOUNDED or CURRENT ROW");
    goto windowAllocErr;
  }

  /* Additionally, the
  ** starting boundary type may not occur earlier in the following list than
  ** the ending boundary type:
  **
  **   UNBOUNDED PRECEDING
  **   <expr> PRECEDING
  **   CURRENT ROW
  **   <expr> FOLLOWING
  **   UNBOUNDED FOLLOWING
  **
  ** The parser ensures that "UNBOUNDED PRECEDING" cannot be used as an ending
  ** boundary, and than "UNBOUNDED FOLLOWING" cannot be used as a starting
  ** frame boundary.
  */

  if( (eStart==TK_CURRENT && eEnd==TK_PRECEDING)
   || (eStart==TK_FOLLOWING && (eEnd==TK_PRECEDING || eEnd==TK_CURRENT))


  ){
    sqlite3ErrorMsg(pParse, "unsupported frame delimiter for ROWS");

    goto windowAllocErr;
  }

  pWin = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
  if( pWin==0 ) goto windowAllocErr;

  pWin->eType = eType;
  pWin->eStart = eStart;
  pWin->eEnd = eEnd;
  pWin->pEnd = sqlite3WindowOffsetExpr(pParse, pEnd);
  pWin->pStart = sqlite3WindowOffsetExpr(pParse, pStart);
  return pWin;

windowAllocErr:
  sqlite3ExprDelete(pParse->db, pEnd);
  sqlite3ExprDelete(pParse->db, pStart);


  return 0;
}

/*
** Attach window object pWin to expression p.
*/
void sqlite3WindowAttach(Parse *pParse, Expr *p, Window *pWin){
  if( p ){
    if( pWin ){
      p->pWin = pWin;
      pWin->pOwner = p;
      if( p->flags & EP_Distinct ){
        sqlite3ErrorMsg(pParse,
           "DISTINCT is not supported for window functions");
      }
    }
  }else{
    sqlite3WindowDelete(pParse->db, pWin);
  }
}

/*
** A "PRECEDING <expr>" (bEnd==0) or "FOLLOWING <expr>" (bEnd==1) has just 
** been evaluated and the result left in register reg. This function generates
** VM code to check that the value is a non-negative integer and throws
** an exception if it is not.
*/
static void windowCheckFrameOffset(Parse *pParse, int reg, int bEnd){
  static const char *azErr[] = {
    "frame starting offset must be a non-negative integer",
    "frame ending offset must be a non-negative integer"
  };
  Vdbe *v = sqlite3GetVdbe(pParse);
  int regZero = sqlite3GetTempReg(pParse);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regZero);

  sqlite3VdbeAddOp2(v, OP_OpenDup, csrStart, pMWin->iEphCsr);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrEnd, pMWin->iEphCsr);

  /* If either regStart or regEnd are not non-negative integers, throw 
  ** an exception.  */
  if( pMWin->pStart ){
    sqlite3ExprCode(pParse, pMWin->pStart, regStart);
    windowCheckFrameOffset(pParse, regStart, 0);
  }
  if( pMWin->pEnd ){
    sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);
    windowCheckFrameOffset(pParse, regEnd, 1);
  }

  /* If this is "ROWS <expr1> FOLLOWING AND ROWS <expr2> FOLLOWING", do:
  **
  **   if( regEnd<regStart ){
  **     // The frame always consists of 0 rows
  **     regStart = regSize;

} {
  1 1  2 1,2  3 1,2,3  4 2,3,4  5 3,4,5
}
do_catchsql_test 9.1 {
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
  SELECT x, group_concat(x) OVER (ORDER BY x RANGE 2 PRECEDING)
  FROM c;
} {1 {RANGE must use only UNBOUNDED or CURRENT ROW}}

do_catchsql_test 9.2 {
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
  SELECT x, group_concat(x) OVER (ORDER BY x RANGE BETWEEN UNBOUNDED PRECEDING AND 2 FOLLOWING)
  FROM c;
} {1 {RANGE must use only UNBOUNDED or CURRENT ROW}}

do_catchsql_test 9.3 {
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
  SELECT count(DISTINCT x) OVER (ORDER BY x) FROM c;
} {1 {DISTINCT is not supported for window functions}}

do_catchsql_test 9.4 {

} {1 {near "PRECEDING": syntax error}}

foreach {tn frame} {
  1 "BETWEEN CURRENT ROW AND 4 PRECEDING"
  2 "4 FOLLOWING"
  3 "BETWEEN 4 FOLLOWING AND CURRENT ROW"
  4 "BETWEEN 4 FOLLOWING AND 2 PRECEDING"


} {
  do_catchsql_test 9.7.$tn "
    WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
    SELECT count() OVER (
        ORDER BY x ROWS $frame 
    ) FROM c;
  " {1 {unsupported frame delimiter for ROWS}}
}

do_catchsql_test 9.8.1 {
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
  SELECT count() OVER (
      ORDER BY x ROWS BETWEEN a PRECEDING AND 2 FOLLOWING
  ) FROM c;
} {1 {frame starting offset must be a non-negative integer}}
do_catchsql_test 9.8.2 {
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<5)
  SELECT count() OVER (
      ORDER BY x ROWS BETWEEN 2 PRECEDING AND a FOLLOWING
  ) FROM c;
} {1 {frame ending offset must be a non-negative integer}}


finish_test