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Provide moving-aggregate support for a bunch of numerical aggregates.

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First installment of the promised moving-aggregate support in built-in
aggregates: count(), sum(), avg(), stddev() and variance() for
assorted datatypes, though not for float4/float8.

In passing, remove a 2001-vintage kluge in interval_accum(): interval
array elements have been properly aligned since around 2003, but
nobody remembered to take out this workaround.  Also, fix a thinko
in the opr_sanity tests for moving-aggregate catalog entries.

David Rowley and Florian Pflug, reviewed by Dean Rasheed
This commit is contained in:
Tom Lane
2014-04-12 20:33:09 -04:00
parent a9d9acbf21
commit 9d229f399e
13 changed files with 1232 additions and 224 deletions
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72
src/backend/utils/adt/timestamp.c
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@ -3229,7 +3229,6 @@ interval_mi(PG_FUNCTION_ARGS)
(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
errmsg("interval out of range")));
PG_RETURN_INTERVAL_P(result);
}
@ -3376,12 +3375,18 @@ interval_div(PG_FUNCTION_ARGS)
}
/*
* interval_accum and interval_avg implement the AVG(interval) aggregate.
* interval_accum, interval_accum_inv, and interval_avg implement the
* AVG(interval) aggregate.
*
* The transition datatype for this aggregate is a 2-element array of
* intervals, where the first is the running sum and the second contains
* the number of values so far in its 'time' field. This is a bit ugly
* but it beats inventing a specialized datatype for the purpose.
*
* NOTE: The inverse transition function cannot guarantee exact results
* when using float8 timestamps. However, int8 timestamps are now the
* norm, and the probable range of values is not so wide that disastrous
* cancellation is likely even with float8, so we'll ignore the risk.
*/
Datum
@ -3402,17 +3407,8 @@ interval_accum(PG_FUNCTION_ARGS)
if (ndatums != 2)
elog(ERROR, "expected 2-element interval array");
/*
* XXX memcpy, instead of just extracting a pointer, to work around buggy
* array code: it won't ensure proper alignment of Interval objects on
* machines where double requires 8-byte alignment. That should be fixed,
* but in the meantime...
*
* Note: must use DatumGetPointer here, not DatumGetIntervalP, else some
* compilers optimize into double-aligned load/store anyway.
*/
memcpy((void *) &sumX, DatumGetPointer(transdatums[0]), sizeof(Interval));
memcpy((void *) &N, DatumGetPointer(transdatums[1]), sizeof(Interval));
sumX = *(DatumGetIntervalP(transdatums[0]));
N = *(DatumGetIntervalP(transdatums[1]));
newsum = DatumGetIntervalP(DirectFunctionCall2(interval_pl,
IntervalPGetDatum(&sumX),
@ -3428,6 +3424,41 @@ interval_accum(PG_FUNCTION_ARGS)
PG_RETURN_ARRAYTYPE_P(result);
}
Datum
interval_accum_inv(PG_FUNCTION_ARGS)
{
ArrayType *transarray = PG_GETARG_ARRAYTYPE_P(0);
Interval *newval = PG_GETARG_INTERVAL_P(1);
Datum *transdatums;
int ndatums;
Interval sumX,
N;
Interval *newsum;
ArrayType *result;
deconstruct_array(transarray,
INTERVALOID, sizeof(Interval), false, 'd',
&transdatums, NULL, &ndatums);
if (ndatums != 2)
elog(ERROR, "expected 2-element interval array");
sumX = *(DatumGetIntervalP(transdatums[0]));
N = *(DatumGetIntervalP(transdatums[1]));
newsum = DatumGetIntervalP(DirectFunctionCall2(interval_mi,
IntervalPGetDatum(&sumX),
IntervalPGetDatum(newval)));
N.time -= 1;
transdatums[0] = IntervalPGetDatum(newsum);
transdatums[1] = IntervalPGetDatum(&N);
result = construct_array(transdatums, 2,
INTERVALOID, sizeof(Interval), false, 'd');
PG_RETURN_ARRAYTYPE_P(result);
}
Datum
interval_avg(PG_FUNCTION_ARGS)
{
@ -3443,17 +3474,8 @@ interval_avg(PG_FUNCTION_ARGS)
if (ndatums != 2)
elog(ERROR, "expected 2-element interval array");
/*
* XXX memcpy, instead of just extracting a pointer, to work around buggy
* array code: it won't ensure proper alignment of Interval objects on
* machines where double requires 8-byte alignment. That should be fixed,
* but in the meantime...
*
* Note: must use DatumGetPointer here, not DatumGetIntervalP, else some
* compilers optimize into double-aligned load/store anyway.
*/
memcpy((void *) &sumX, DatumGetPointer(transdatums[0]), sizeof(Interval));
memcpy((void *) &N, DatumGetPointer(transdatums[1]), sizeof(Interval));
sumX = *(DatumGetIntervalP(transdatums[0]));
N = *(DatumGetIntervalP(transdatums[1]));
/* SQL defines AVG of no values to be NULL */
if (N.time == 0)
@ -3461,7 +3483,7 @@ interval_avg(PG_FUNCTION_ARGS)
return DirectFunctionCall2(interval_div,
IntervalPGetDatum(&sumX),
Float8GetDatum(N.time));
Float8GetDatum((double) N.time));
}