SQLite

  }
  sqlite3VdbeResolveLabel(v, lblDone);
  if( addrGoto ) sqlite3VdbeJumpHere(v, addrGoto);
  if( addrIf ) sqlite3VdbeJumpHere(v, addrIf);
  return ret;
}


/*
** Allocate and return a duplicate of the Window object indicated by the
** third argument. Set the Window.pOwner field of the new object to
** pOwner.
*/
Window *sqlite3WindowDup(sqlite3 *db, Expr *pOwner, Window *p){
  Window *pNew = 0;
  if( ALWAYS(p) ){
    pNew = sqlite3DbMallocZero(db, sizeof(Window));
    if( pNew ){
      pNew->zName = sqlite3DbStrDup(db, p->zName);
      pNew->pFilter = sqlite3ExprDup(db, p->pFilter, 0);
      pNew->pFunc = p->pFunc;
      pNew->pPartition = sqlite3ExprListDup(db, p->pPartition, 0);
      pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, 0);
      pNew->eType = p->eType;
      pNew->eEnd = p->eEnd;
      pNew->eStart = p->eStart;
      pNew->pStart = sqlite3ExprDup(db, p->pStart, 0);
      pNew->pEnd = sqlite3ExprDup(db, p->pEnd, 0);
      pNew->pOwner = pOwner;
    }
  }
  return pNew;
}

/*
** Return a copy of the linked list of Window objects passed as the
** second argument.
*/
Window *sqlite3WindowListDup(sqlite3 *db, Window *p){
  Window *pWin;
  Window *pRet = 0;
  Window **pp = &pRet;

  for(pWin=p; pWin; pWin=pWin->pNextWin){
    *pp = sqlite3WindowDup(db, 0, pWin);
    if( *pp==0 ) break;
    pp = &((*pp)->pNextWin);
  }

  return pRet;
}

/*
** sqlite3WhereBegin() has already been called for the SELECT statement 
** passed as the second argument when this function is invoked. It generates
** code to populate the Window.regResult register for each window function 
** and invoke the sub-routine at instruction addrGosub once for each row.
** sqlite3WhereEnd() is always called before returning. 
**
** This function handles several different types of window frames, which
** require slightly different processing. The following pseudo code is
** used to implement window frames of the form:
**
**   ROWS BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
**
** Other window frame types use variants of the following:
**
**     ... loop started by sqlite3WhereBegin() ...
**       if( new partition ){
**         Gosub flush
**       }
**       Insert new row into eph table.
**       
**       if( first row of partition ){
**         // Rewind three cursors, all open on the eph table.
**         Rewind(csrEnd);
**         Rewind(csrStart);
**         Rewind(csrCurrent);
**       
**         regEnd = <expr2>          // FOLLOWING expression
**         regStart = <expr1>        // PRECEDING expression
**       }else{
**         // First time this branch is taken, the eph table contains two 
**         // rows. The first row in the partition, which all three cursors
**         // currently point to, and the following row.
**         AGGSTEP
**         if( (regEnd--)<=0 ){

**           RETURN_ROW
**           if( (regStart--)<=0 ){
**             AGGINVERSE

**           }
**         }
**       }

**     }

**     flush:
**       AGGSTEP
**       while( 1 ){
**         RETURN ROW
**         if( csrCurrent is EOF ) break;

**         if( (regStart--)<=0 ){

**           AggInverse(csrStart)
**           Next(csrStart)
**         }
**       }
**
** The pseudo-code above uses the following shorthand:
**
**   AGGSTEP:    invoke the aggregate xStep() function for each window function
**               with arguments read from the current row of cursor csrEnd, then
**               step cursor csrEnd forward one row (i.e. sqlite3BtreeNext()).
**
**   RETURN_ROW: return a row to the caller based on the contents of the 
**               current row of csrCurrent and the current state of all 
**               aggregates. Then step cursor csrCurrent forward one row.
**
**   AGGINVERSE: invoke the aggregate xInverse() function for each window 
**               functions with arguments read from the current row of cursor
**               csrStart. Then step csrStart forward one row.
**
** There are two other ROWS window frames that are handled significantly
** differently from the above - "BETWEEN <expr> PRECEDING AND <expr> PRECEDING"
** and "BETWEEN <expr> FOLLOWING AND <expr> FOLLOWING". These are special 
** cases because they change the order in which the three cursors (csrStart,
** csrCurrent and csrEnd) iterate through the ephemeral table. Cases that
** use UNBOUNDED or CURRENT ROW are much simpler variations on one of these
** three.
**
**   ROWS BETWEEN <expr1> PRECEDING AND <expr2> PRECEDING
**
**     ... loop started by sqlite3WhereBegin() ...
**       if( new partition ){
**         Gosub flush
**       }
**       Insert new row into eph table.
**       if( first row of partition ){
**         Rewind(csrEnd)
**         Rewind(csrStart)
**         Rewind(csrCurrent)
**         regEnd = <expr2>
**         regStart = <expr1>
**       }else{
**         if( (regEnd--)<=0 ){
**           AGGSTEP
**         }
**         RETURN_ROW
**         if( (regStart--)<=0 ){
**           AGGINVERSE
**         }
**       }
**     }
**     flush:
**       if( (regEnd--)<=0 ){
**         AGGSTEP
**       }
**       RETURN_ROW
**
**
**   ROWS BETWEEN <expr1> FOLLOWING AND <expr2> FOLLOWING
**
**     ... loop started by sqlite3WhereBegin() ...
**     if( new partition ){
**       Gosub flush
**     }
**     Insert new row into eph table.
**     if( first row of partition ){
**       Rewind(csrEnd)
**       Rewind(csrStart)
**       Rewind(csrCurrent)
**       regEnd = <expr2>
**       regStart = regEnd - <expr1>
**     }else{
**       AGGSTEP
**       if( (regEnd--)<=0 ){
**         RETURN_ROW
**       }
**       if( (regStart--)<=0 ){
**         AGGINVERSE
**       }
**     }
**   }
**   flush:
**     AGGSTEP
**     while( 1 ){
**       if( (regEnd--)<=0 ){
**         RETURN_ROW
**         if( eof ) break;
**       }
**       if( (regStart--)<=0 ){
**         AGGINVERSE
**         if( eof ) break
**       }
**     }
**     while( !eof csrCurrent ){
**       RETURN_ROW
**     }
**
** For the most part, the patterns above are adapted to support UNBOUNDED by
** assuming that it is equivalent to "infinity PRECEDING/FOLLOWING" and
** CURRENT ROW by assuming that it is equivilent to "0 PRECEDING/FOLLOWING".
** This is optimized of course - branches that will never be taken and
** conditions that are always true are omitted from the VM code. The only
** exceptional case is:
**
**   ROWS BETWEEN <expr1> FOLLOWING AND UNBOUNDED FOLLOWING
**
**     ... loop started by sqlite3WhereBegin() ...
**     if( new partition ){
**       Gosub flush
**     }
**     Insert new row into eph table.
**     if( first row of partition ){
**       Rewind(csrEnd)
**       Rewind(csrStart)
**       Rewind(csrCurrent)
**       regStart = <expr1>
**     }else{
**       AGGSTEP
**     }
**   }
**   flush:
**     AGGSTEP
**     while( 1 ){
**       if( (regStart--)<=0 ){
**         AGGINVERSE
**         if( eof ) break
**       }
**       RETURN_ROW
**     }
**     while( !eof csrCurrent ){
**       RETURN_ROW
**     }
**
** Sometimes, this function generates code to run in "cache mode" - meaning
** the entire partition is cached in the ephemeral table before any of its
** rows are processed, instead of processing rows as the sub-select delivers
** them. This is required by certain built-in window functions, for example
** percent_rank() or lead(). In that case, the relevant pseudo-code above
** is modified to:
**
**     ... loop started by sqlite3WhereBegin() ...
**     if( new partition ){
**       Gosub flush
**     }
**     Insert new row into eph table.
**   }
**   flush:
**     for each row in eph table {
**
** followed immediately by the code that usually follows the "Insert new row
** into eph table." line.
**
*/
void sqlite3WindowCodeStep(
    Parse *pParse,                  /* Parse context */
  Select *p,                      /* Rewritten SELECT statement */
  WhereInfo *pWInfo,              /* Context returned by sqlite3WhereBegin() */
  int regGosub,                   /* Register for OP_Gosub */
  int addrGosub                   /* OP_Gosub here to return each row */
){
  Window *pMWin = p->pWin;
  ExprList *pOrderBy = pMWin->pOrderBy;
  Vdbe *v = sqlite3GetVdbe(pParse);
  int bCache;                     /* True if generating "cache-mode" code */
  int regFlushPart;               /* Register for "Gosub flush_partition" */
  int csrWrite;                   /* Cursor used to write to eph. table */



  int csrInput = p->pSrc->a[0].iCursor;     /* Cursor of sub-select */
  int nInput = p->pSrc->a[0].pTab->nCol;    /* Number of cols returned by sub */
  int iInput;                               /* To iterate through sub cols */

  int addrGoto;                   /* Address of OP_Goto */
  int addrIfNot;                  /* Address of OP_IfNot */
  int addrGosubFlush;             /* Address of OP_Gosub to flush: */
  int addrInteger;                /* Address of OP_Integer */
  int addrCacheRewind;            /* Address of OP_Rewind used in cache-mode */
  int addrCacheNext;              /* Jump here for next row in cache-mode */

  int addrShortcut = 0;
  int addrEmpty = 0;              /* Address of OP_Rewind in flush: */
  int addrPeerJump = 0;           /* Address of jump taken if not new peer */



  int regStart = 0;               /* Value of <expr> PRECEDING */
  int regEnd = 0;                 /* Value of <expr> FOLLOWING */
  int regNew;                     /* Array of registers holding new input row */

  int regRecord;                  /* regNew array in record form */
  int regRowid;                   /* Rowid for regRecord in eph table */
  int regNewPeer = 0;             /* Peer values for new row (part of regNew) */
  int regPeer = 0;                /* Peer values for current row */

  WindowCodeArg s;                /* Context object for sub-routines */

  assert( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_CURRENT 
       || pMWin->eStart==TK_FOLLOWING || pMWin->eStart==TK_UNBOUNDED 
  );
  assert( pMWin->eEnd==TK_FOLLOWING || pMWin->eEnd==TK_CURRENT 
       || pMWin->eEnd==TK_UNBOUNDED || pMWin->eEnd==TK_PRECEDING 
  );

  /* Determine whether or not each partition will be cached before beginning
  ** to process rows within it.  */
  bCache = windowCachePartition(pMWin);

  /* Fill in the context object */
  memset(&s, 0, sizeof(WindowCodeArg));
  s.pParse = pParse;
  s.pMWin = pMWin;
  s.pVdbe = v;
  s.regGosub = regGosub;
  s.addrGosub = addrGosub;
  s.current.csr = pMWin->iEphCsr;
  csrWrite = s.current.csr+1;
  s.start.csr = s.current.csr+2;
  s.end.csr = s.current.csr+3;

  regNew = pParse->nMem+1;
  pParse->nMem += nInput;
  regRecord = ++pParse->nMem;
  regRowid = ++pParse->nMem;
  regFlushPart = ++pParse->nMem;

  /* If the window frame contains an "<expr> PRECEDING" or "<expr> FOLLOWING"
  ** clause, allocate registers to store the results of evaluating each
  ** <expr>.  */
  if( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_FOLLOWING ){
    regStart = ++pParse->nMem;
  }
  if( pMWin->eEnd==TK_PRECEDING || pMWin->eEnd==TK_FOLLOWING ){
    regEnd = ++pParse->nMem;
  }

  /* If this is not a "ROWS BETWEEN ..." frame, then allocate arrays of
  ** registers to store copies of the ORDER BY expressions (peer values) 
  ** for the main loop, and for each cursor (start, current and end). */
  if( pMWin->eType!=TK_ROWS ){
    int nPeer = (pOrderBy ? pOrderBy->nExpr : 0);
    regNewPeer = regNew + pMWin->nBufferCol;
    if( pMWin->pPartition ) regNewPeer += pMWin->pPartition->nExpr;

    regPeer = pParse->nMem+1;       pParse->nMem += nPeer;
    s.start.reg = pParse->nMem+1;   pParse->nMem += nPeer;
    s.current.reg = pParse->nMem+1; pParse->nMem += nPeer;
    s.end.reg = pParse->nMem+1;     pParse->nMem += nPeer;
  }

  /* Load the column values for the row returned by the sub-select
  ** into an array of registers starting at regNew. Assemble them into
  ** a record in register regRecord. */
  for(iInput=0; iInput<nInput; iInput++){
    sqlite3VdbeAddOp3(v, OP_Column, csrInput, iInput, regNew+iInput);
  }
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regNew, nInput, regRecord);

  /* An input row has just been read into an array of registers starting
  ** at regNew. If the window has a PARTITION clause, this block generates 
  ** VM code to check if the input row is the start of a new partition.
  ** If so, it does an OP_Gosub to an address to be filled in later. The
  ** address of the OP_Gosub is stored in local variable addrGosubFlush. */

  if( pMWin->pPartition ){
    int addr;
    ExprList *pPart = pMWin->pPartition;
    int nPart = pPart->nExpr;
    int regNewPart = regNew + pMWin->nBufferCol;
    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);

    addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart, nPart);
    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
    sqlite3VdbeAddOp3(v, OP_Jump, addr+2, addr+4, addr+2);
    VdbeCoverageEqNe(v);
    addrGosubFlush = sqlite3VdbeAddOp1(v, OP_Gosub, regFlushPart);

    sqlite3WhereEnd(pWInfo);
    addrInteger = sqlite3VdbeAddOp2(v, OP_Integer, 0, regFlushPart);
    if( pMWin->pPartition ){
      sqlite3VdbeJumpHere(v, addrGosubFlush);
    }
    addrCacheRewind = sqlite3VdbeAddOp1(v, OP_Rewind, csrWrite);
  }else{
    addrIfNot = sqlite3VdbeAddOp1(v, OP_IfNot, pMWin->regFirst);
  }

  /* This block is run for the first row of each partition */
  s.regArg = windowInitAccum(pParse, pMWin);

  if( regStart ){
    sqlite3ExprCode(pParse, pMWin->pStart, regStart);
    windowCheckIntValue(pParse, regStart, 0);
  }
  if( regEnd ){
    sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);

    sqlite3VdbeAddOp3(v, OP_Copy, regPeer, s.end.reg, pOrderBy->nExpr-1);
  }

  sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regFirst);
  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Begin generating SECOND_ROW_CODE */
  VdbeModuleComment((pParse->pVdbe, "Begin WindowCodeStep.SECOND_ROW"));
  if( bCache ){
    addrCacheNext = sqlite3VdbeCurrentAddr(v);
    if( pMWin->eType!=TK_ROWS ){
      windowReadPeerValues(&s, csrWrite, regNewPeer);
    }
  }else{
    sqlite3VdbeJumpHere(v, addrIfNot);
  }
  if( regPeer ){
    addrPeerJump = windowIfNewPeer(pParse, pOrderBy, regNewPeer, regPeer);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, 0, 0);
    if( pMWin->eEnd!=TK_UNBOUNDED ){

        if( regEnd ) sqlite3VdbeJumpHere(v, addr);
      }
    }
  }
  if( addrPeerJump ){
    sqlite3VdbeJumpHere(v, addrPeerJump);
  }
  VdbeModuleComment((pParse->pVdbe, "End WindowCodeStep.SECOND_ROW"));

  /* End of the main input loop */
  sqlite3VdbeJumpHere(v, addrGoto);
  if( bCache ){
    sqlite3VdbeAddOp2(v, OP_Next, csrWrite, addrCacheNext);
    sqlite3VdbeJumpHere(v, addrCacheRewind); 
  }else{
    if( addrShortcut>0 ) sqlite3VdbeJumpHere(v, addrShortcut);
    sqlite3WhereEnd(pWInfo);
  }

  /* Fall through */
  if( pMWin->pPartition && bCache==0 ){
    addrInteger = sqlite3VdbeAddOp2(v, OP_Integer, 0, regFlushPart);
    sqlite3VdbeJumpHere(v, addrGosubFlush);
  }

  VdbeModuleComment((pParse->pVdbe, "Begin WindowCodeStep.FLUSH"));
  addrEmpty = sqlite3VdbeAddOp1(v, OP_Rewind, csrWrite);
  if( pMWin->eEnd==TK_PRECEDING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, regEnd, 0);
    windowCodeOp(&s, WINDOW_RETURN_ROW, 0, 0);
  }else if( pMWin->eStart==TK_FOLLOWING ){
    int addrStart;
    int addrBreak1;

  sqlite3VdbeJumpHere(v, addrEmpty);

  if( bCache && addrShortcut>0 ) sqlite3VdbeJumpHere(v, addrShortcut);
  sqlite3VdbeAddOp1(v, OP_ResetSorter, s.current.csr);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regSize);
  if( bCache==0 ) sqlite3VdbeAddOp2(v, OP_Integer, 1, pMWin->regFirst);
  VdbeModuleComment((pParse->pVdbe, "End WindowCodeStep.FLUSH"));
  if( pMWin->pPartition ){
    sqlite3VdbeChangeP1(v, addrInteger, sqlite3VdbeCurrentAddr(v));
    sqlite3VdbeAddOp1(v, OP_Return, regFlushPart);
  }
}

































































#endif /* SQLITE_OMIT_WINDOWFUNC */