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/*
* eval_windowaggregates
* evaluate plain aggregates being used as window functions
*
* This differs from nodeAgg.c in two ways. First, if the window's frame
* start position moves, we use the inverse transition function (if it exists)
* to remove rows from the transition value. And second, we expect to be
* able to call aggregate final functions repeatedly after aggregating more
* data onto the same transition value. This is not a behavior required by
* nodeAgg.c.
*/
static void
eval_windowaggregates(WindowAggState *winstate)
{
WindowStatePerAgg peraggstate;
int wfuncno,
numaggs,
numaggs_restart,
i;
int64 aggregatedupto_nonrestarted;
MemoryContext oldContext;
ExprContext *econtext;
WindowObject agg_winobj;
TupleTableSlot *agg_row_slot;
TupleTableSlot *temp_slot;
numaggs = winstate->numaggs;
if (numaggs == 0)
return; /* nothing to do */
/* final output execution is in ps_ExprContext */
econtext = winstate->ss.ps.ps_ExprContext;
agg_winobj = winstate->agg_winobj;
agg_row_slot = winstate->agg_row_slot;
temp_slot = winstate->temp_slot_1;
/*
* If the window's frame start clause is UNBOUNDED_PRECEDING and no
* exclusion clause is specified, then the window frame consists of a
* contiguous group of rows extending forward from the start of the
* partition, and rows only enter the frame, never exit it, as the current
* row advances forward. This makes it possible to use an incremental
* strategy for evaluating aggregates: we run the transition function for
* each row added to the frame, and run the final function whenever we
* need the current aggregate value. This is considerably more efficient
* than the naive approach of re-running the entire aggregate calculation
* for each current row. It does assume that the final function doesn't
* damage the running transition value, but we have the same assumption in
* nodeAgg.c too (when it rescans an existing hash table).
*
* If the frame start does sometimes move, we can still optimize as above
* whenever successive rows share the same frame head, but if the frame
* head moves beyond the previous head we try to remove those rows using
* the aggregate's inverse transition function. This function restores
* the aggregate's current state to what it would be if the removed row
* had never been aggregated in the first place. Inverse transition
* functions may optionally return NULL, indicating that the function was
* unable to remove the tuple from aggregation. If this happens, or if
* the aggregate doesn't have an inverse transition function at all, we
* must perform the aggregation all over again for all tuples within the
* new frame boundaries.
*
* If there's any exclusion clause, then we may have to aggregate over a
* non-contiguous set of rows, so we punt and recalculate for every row.
* (For some frame end choices, it might be that the frame is always
* contiguous anyway, but that's an optimization to investigate later.)
*
* In many common cases, multiple rows share the same frame and hence the
* same aggregate value. (In particular, if there's no ORDER BY in a RANGE
* window, then all rows are peers and so they all have window frame equal
* to the whole partition.) We optimize such cases by calculating the
* aggregate value once when we reach the first row of a peer group, and
* then returning the saved value for all subsequent rows.
*
* 'aggregatedupto' keeps track of the first row that has not yet been
* accumulated into the aggregate transition values. Whenever we start a
* new peer group, we accumulate forward to the end of the peer group.
*/
/*
* First, update the frame head position.
*
* The frame head should never move backwards, and the code below wouldn't
* cope if it did, so for safety we complain if it does.
*/
update_frameheadpos(winstate);
if (winstate->frameheadpos < winstate->aggregatedbase)
elog(ERROR, "window frame head moved backward");
/*
* If the frame didn't change compared to the previous row, we can re-use
* the result values that were previously saved at the bottom of this
* function. Since we don't know the current frame's end yet, this is not
* possible to check for fully. But if the frame end mode is UNBOUNDED
* FOLLOWING or CURRENT ROW, no exclusion clause is specified, and the
* current row lies within the previous row's frame, then the two frames'
* ends must coincide. Note that on the first row aggregatedbase ==
* aggregatedupto, meaning this test must fail, so we don't need to check
* the "there was no previous row" case explicitly here.
*/
if (winstate->aggregatedbase == winstate->frameheadpos &&
(winstate->frameOptions & (FRAMEOPTION_END_UNBOUNDED_FOLLOWING |
FRAMEOPTION_END_CURRENT_ROW)) &&
!(winstate->frameOptions & FRAMEOPTION_EXCLUSION) &&
winstate->aggregatedbase <= winstate->currentpos &&
winstate->aggregatedupto > winstate->currentpos)
{
for (i = 0; i < numaggs; i++)
{
peraggstate = &winstate->peragg[i];
wfuncno = peraggstate->wfuncno;
econtext->ecxt_aggvalues[wfuncno] = peraggstate->resultValue;
econtext->ecxt_aggnulls[wfuncno] = peraggstate->resultValueIsNull;
}
return;
}
/*----------
* Initialize restart flags.
*
* We restart the aggregation:
* - if we're processing the first row in the partition, or
* - if the frame's head moved and we cannot use an inverse
* transition function, or
* - we have an EXCLUSION clause, or
* - if the new frame doesn't overlap the old one
*
* Note that we don't strictly need to restart in the last case, but if
* we're going to remove all rows from the aggregation anyway, a restart
* surely is faster.
*----------
*/
numaggs_restart = 0;
for (i = 0; i < numaggs; i++)
{
peraggstate = &winstate->peragg[i];
if (winstate->currentpos == 0 ||
(winstate->aggregatedbase != winstate->frameheadpos &&
!OidIsValid(peraggstate->invtransfn_oid)) ||
(winstate->frameOptions & FRAMEOPTION_EXCLUSION) ||
winstate->aggregatedupto <= winstate->frameheadpos)
{
peraggstate->restart = true;
numaggs_restart++;
}
else
peraggstate->restart = false;
}
/*
* If we have any possibly-moving aggregates, attempt to advance
* aggregatedbase to match the frame's head by removing input rows that
* fell off the top of the frame from the aggregations. This can fail,
* i.e. advance_windowaggregate_base() can return false, in which case
* we'll restart that aggregate below.
*/
while (numaggs_restart < numaggs &&
winstate->aggregatedbase < winstate->frameheadpos)
{
/*
* Fetch the next tuple of those being removed. This should never fail
* as we should have been here before.
*/
if (!window_gettupleslot(agg_winobj, winstate->aggregatedbase,
temp_slot))
elog(ERROR, "could not re-fetch previously fetched frame row");
/* Set tuple context for evaluation of aggregate arguments */
winstate->tmpcontext->ecxt_outertuple = temp_slot;
/*
* Perform the inverse transition for each aggregate function in the
* window, unless it has already been marked as needing a restart.
*/
for (i = 0; i < numaggs; i++)
{
bool ok;
peraggstate = &winstate->peragg[i];
if (peraggstate->restart)
continue;
wfuncno = peraggstate->wfuncno;
ok = advance_windowaggregate_base(winstate,
&winstate->perfunc[wfuncno],
peraggstate);
if (!ok)
{
/* Inverse transition function has failed, must restart */
peraggstate->restart = true;
numaggs_restart++;
}
}
/* Reset per-input-tuple context after each tuple */
ResetExprContext(winstate->tmpcontext);
/* And advance the aggregated-row state */
winstate->aggregatedbase++;
ExecClearTuple(temp_slot);
}
/*
* If we successfully advanced the base rows of all the aggregates,
* aggregatedbase now equals frameheadpos; but if we failed for any, we
* must forcibly update aggregatedbase.
*/
winstate->aggregatedbase = winstate->frameheadpos;
/*
* If we created a mark pointer for aggregates, keep it pushed up to frame
* head, so that tuplestore can discard unnecessary rows.
*/
if (agg_winobj->markptr >= 0)
WinSetMarkPosition(agg_winobj, winstate->frameheadpos);
/*
* Now restart the aggregates that require it.
*
* We assume that aggregates using the shared context always restart if
* *any* aggregate restarts, and we may thus clean up the shared
* aggcontext if that is the case. Private aggcontexts are reset by
* initialize_windowaggregate() if their owning aggregate restarts. If we
* aren't restarting an aggregate, we need to free any previously saved
* result for it, else we'll leak memory.
*/
if (numaggs_restart > 0)
MemoryContextResetAndDeleteChildren(winstate->aggcontext);
for (i = 0; i < numaggs; i++)
{
peraggstate = &winstate->peragg[i];
/* Aggregates using the shared ctx must restart if *any* agg does */
Assert(peraggstate->aggcontext != winstate->aggcontext ||
numaggs_restart == 0 ||
peraggstate->restart);
if (peraggstate->restart)
{
wfuncno = peraggstate->wfuncno;
initialize_windowaggregate(winstate,
&winstate->perfunc[wfuncno],
peraggstate);
}
else if (!peraggstate->resultValueIsNull)
{
if (!peraggstate->resulttypeByVal)
pfree(DatumGetPointer(peraggstate->resultValue));
peraggstate->resultValue = (Datum) 0;
peraggstate->resultValueIsNull = true;
}
}
/*
* Non-restarted aggregates now contain the rows between aggregatedbase
* (i.e., frameheadpos) and aggregatedupto, while restarted aggregates
* contain no rows. If there are any restarted aggregates, we must thus
* begin aggregating anew at frameheadpos, otherwise we may simply
* continue at aggregatedupto. We must remember the old value of
* aggregatedupto to know how long to skip advancing non-restarted
* aggregates. If we modify aggregatedupto, we must also clear
* agg_row_slot, per the loop invariant below.
*/
aggregatedupto_nonrestarted = winstate->aggregatedupto;
if (numaggs_restart > 0 &&
winstate->aggregatedupto != winstate->frameheadpos)
{
winstate->aggregatedupto = winstate->frameheadpos;
ExecClearTuple(agg_row_slot);
}
/*
* Advance until we reach a row not in frame (or end of partition).
*
* Note the loop invariant: agg_row_slot is either empty or holds the row
* at position aggregatedupto. We advance aggregatedupto after processing
* a row.
*/
winstate->p = malloc(sizeof(Datum) * 100);
if (!winstate->first_run)
{
winstate->aggregatedupto = 0;
for (;;)
{
int ret;
/* Fetch next row if we didn't already */
window_gettupleslot(agg_winobj, winstate->aggregatedupto,
agg_row_slot);
/* must be end of partition */
if (winstate->aggregatedupto >= winstate->spooled_rows)
break;
/*
* Exit loop if no more rows can be in frame. Skip aggregation if
* current row is not in frame but there might be more in the frame.
*/
/* Set tuple context for evaluation of aggregate arguments */
winstate->tmpcontext->ecxt_outertuple = agg_row_slot;
/* Accumulate row into the aggregates */
for (i = 0; i < numaggs; i++)
{
peraggstate = &winstate->peragg[i];
/* Non-restarted aggs skip until aggregatedupto_nonrestarted */
if (!peraggstate->restart &&
winstate->aggregatedupto < aggregatedupto_nonrestarted)
continue;
wfuncno = peraggstate->wfuncno;
advance_windowaggregate(winstate,
&winstate->perfunc[wfuncno],
peraggstate);
}
/* Reset per-input-tuple context after each tuple */
ResetExprContext(winstate->tmpcontext);
/* And advance the aggregated-row state */
winstate->aggregatedupto++;
ExecClearTuple(agg_row_slot);
}
winstate->first_run = false;
ExecClearTuple(agg_row_slot);
winstate->aggregatedupto = 0;
printf("\n");
printf("the data we extracted :\n");
for (int temp = 1; temp <= winstate->spooled_rows; temp++)
printf("%d\t", winstate->p[temp]);
printf("\n");
}
for (;;)
{
int ret;
/* Fetch next row if we didn't already */
if (TupIsNull(agg_row_slot))
{
if (!window_gettupleslot(agg_winobj, winstate->aggregatedupto,
agg_row_slot))
break; /* must be end of partition */
}
/*
* Exit loop if no more rows can be in frame. Skip aggregation if
* current row is not in frame but there might be more in the frame.
*/
ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
if (ret < 0)
break;
if (ret == 0)
goto next_tuple;
/* Set tuple context for evaluation of aggregate arguments */
winstate->tmpcontext->ecxt_outertuple = agg_row_slot;
/* Accumulate row into the aggregates */
for (i = 0; i < numaggs; i++)
{
peraggstate = &winstate->peragg[i];
/* Non-restarted aggs skip until aggregatedupto_nonrestarted */
if (!peraggstate->restart &&
winstate->aggregatedupto < aggregatedupto_nonrestarted)
continue;
wfuncno = peraggstate->wfuncno;
advance_windowaggregate(winstate,
&winstate->perfunc[wfuncno],
peraggstate);
}
next_tuple:
/* Reset per-input-tuple context after each tuple */
ResetExprContext(winstate->tmpcontext);
/* And advance the aggregated-row state */
winstate->aggregatedupto++;
ExecClearTuple(agg_row_slot);
}
/* The frame's end is not supposed to move backwards, ever */
Assert(aggregatedupto_nonrestarted <= winstate->aggregatedupto);
/*
* finalize aggregates and fill result/isnull fields.
*/
for (i = 0; i < numaggs; i++)
{
Datum *result;
bool *isnull;
peraggstate = &winstate->peragg[i];
wfuncno = peraggstate->wfuncno;
result = &econtext->ecxt_aggvalues[wfuncno];
isnull = &econtext->ecxt_aggnulls[wfuncno];
finalize_windowaggregate(winstate,
&winstate->perfunc[wfuncno],
peraggstate,
result, isnull);
/*
* save the result in case next row shares the same frame.
*
* XXX in some framing modes, eg ROWS/END_CURRENT_ROW, we can know in
* advance that the next row can't possibly share the same frame. Is
* it worth detecting that and skipping this code?
*/
if (!peraggstate->resulttypeByVal && !*isnull)
{
oldContext = MemoryContextSwitchTo(peraggstate->aggcontext);
peraggstate->resultValue =
datumCopy(*result,
peraggstate->resulttypeByVal,
peraggstate->resulttypeLen);
MemoryContextSwitchTo(oldContext);
}
else
{
peraggstate->resultValue = *result;
}
peraggstate->resultValueIsNull = *isnull;
//*result = Int64GetDatum(234);
Numeric ppp = (Numeric)*result;
printf("the aggregate data :%d\n", *result);
}
printf("\nwe have aggregate %dth tuple\n", winstate->count);
winstate->count++;
}