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Add comments to window.c describing how other window frames will be implemented.

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FossilOrigin-Name: 16168146b202915252f9375aef38e65ca20c5d4aa906e851d4d3a484db57562d
This commit is contained in:
dan
2018-05-22 20:35:37 +00:00
parent f9eae18b56
commit 8471be3311
5 changed files with 115 additions and 21 deletions
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90
src/window.c
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@@ -155,21 +155,87 @@ void sqlite3WindowCodeInit(Parse *pParse, Window *pWin){
**
**========================================================================
**
** ROWS BETWEEN UNBOUNDED PRECEDING AND <expr> PRECEDING
** ROWS BETWEEN <expr> PRECEDING AND <expr> PRECEDING
** ROWS BETWEEN <expr> PRECEDING AND CURRENT ROW
** ROWS BETWEEN UNBOUNDED PRECEDING AND <expr> FOLLOWING
** ROWS BETWEEN <expr> PRECEDING AND <expr> FOLLOWING
** ROWS BETWEEN CURRENT ROW AND <expr> FOLLOWING
** ROWS BETWEEN <expr> FOLLOWING AND <expr> FOLLOWING
** ROWS BETWEEN <expr> PRECEDING AND UNBOUNDED FOLLOWING
** ROWS BETWEEN <expr> FOLLOWING AND UNBOUNDED FOLLOWING
**
** Cases that involve <expr> PRECEDING or <expr> FOLLOWING.
**
** ...
** if( new partition ){
** Gosub flush_partition
** }
** Insert (record in eph-table)
** sqlite3WhereEnd()
** Gosub flush_partition
**
** flush_partition:
** OpenDup (csr -> csr2)
** OpenDup (csr -> csr3)
** regPrec = <expr1> // PRECEDING expression
** regFollow = <expr2> // FOLLOWING expression
** if( regPrec<0 || regFollow<0 ) throw exception!
** Rewind (csr,csr2,csr3) // if EOF goto flush_partition_done
** Aggstep (csr3)
** Next(csr3) // if EOF fall-through
** if( (regFollow--)<=0 ){
** AggFinal (xValue)
** Gosub addrGosub
** Next(csr) // if EOF goto flush_partition_done
** if( (regPrec--)<=0 ){
** AggStep (csr2, xInverse)
** Next(csr2)
** }
** }
** flush_partition_done:
** Close (csr2)
** Close (csr3)
** ResetSorter (csr)
** Return
**
** ROWS BETWEEN <expr> PRECEDING AND CURRENT ROW
** ROWS BETWEEN CURRENT ROW AND <expr> FOLLOWING
** ROWS BETWEEN <expr> PRECEDING AND UNBOUNDED FOLLOWING
** ROWS BETWEEN UNBOUNDED PRECEDING AND <expr> FOLLOWING
**
** These are similar to the above. For "CURRENT ROW", intialize the
** register to 0. For "UNBOUNDED ..." to infinity.
**
** ROWS BETWEEN <expr> PRECEDING AND <expr> PRECEDING
**
** Replace the bit after "Rewind" in the above with:
**
** if( (regFollow--)<=0 ){
** AggStep (csr3)
** Next (csr3)
** }
** AggFinal (xValue)
** Gosub addrGosub
** Next(csr) // if EOF goto flush_partition_done
** if( (regPrec--)<=0 ){
** AggStep (csr2, xInverse)
** Next (csr2)
** }
**
** ROWS BETWEEN <expr> FOLLOWING AND <expr> FOLLOWING
**
** regFollow = regFollow - regPrec
** Rewind (csr,csr2,csr3) // if EOF goto flush_partition_done
** Aggstep (csr3)
** Next(csr3) // if EOF fall-through
** if( (regFollow--)<=0 ){
** AggStep (csr2, xInverse)
** Next (csr2)
** if( (regPrec--)<=0 ){
** AggFinal (xValue)
** Gosub addrGosub
** Next(csr) // if EOF goto flush_partition_done
** }
** }
**
** ROWS BETWEEN UNBOUNDED PRECEDING AND <expr> PRECEDING
** ROWS BETWEEN <expr> FOLLOWING AND UNBOUNDED FOLLOWING
**
** Similar to the above, except with regPrec or regFollow set to infinity,
** as appropriate.
**
**
**
*/
void sqlite3WindowCodeStep(
@@ -210,7 +276,7 @@ void sqlite3WindowCodeStep(
if( pPart ){
int regNewPart = reg + pMWin->nBufferCol;
KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);
addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart, nPart);
addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart,nPart);
sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
addrJump = sqlite3VdbeAddOp3(v, OP_Jump, addr+2, 0, addr+2);
for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
@@ -245,7 +311,7 @@ void sqlite3WindowCodeStep(
sqlite3VdbeAddOp1(v, OP_ResetSorter, pMWin->iEphCsr);
sqlite3VdbeAddOp3(
v, OP_Copy, reg+pMWin->nBufferCol, pMWin->regPart, nPart+nPeer-1
);
);
sqlite3VdbeJumpHere(v, addrJump);
}