Hi,
I know that i am not Firebird core developer and I have less influence.
But, why do you still say about WHILE, SUSSPEND, YIELD, FETCH if there is
simple alternative to not have it at all?
Can someone tell me what is wrong with my proposition?
------------------------------------------------------------------
Instead of simple
create aggregate function custom_sum (i integer) returns (o integer)
as
begin
if (i is not null) then
begin
if (o is null) then
o = 0;
o = o + i;
end
end
you propose something like this
create aggregate function custom_sum (i integer) returns (o integer)
as
begin
while (not agg_finished)
do
begin
if (i is not null) then
begin
if (o is null) then
o = 0;
o = o + i;
end
suspend;
end
end
------------------------------------------------------------------
instead of simple:
create aggregate function custom_avg (i double precision) returns (o double
precision)
as
declare accumulated double precision = 0;
begin
if (i is not null) then
accumulated = accumulated + i;
if (agg_result_needed and (accumulated is not null) then
o = accumulated / agg_i;
end
you propose:
create aggregate function custom_avg (i double precision) returns (o double
precision)
as
declare count integer = 0;
declare accumulated double precision = 0;
begin
while (not agg_finished)
do
begin
if (i is not null) then
begin
count = count + 1;
accumulated = accumulated + i;
o = accumulated / count;
end
suspend;
end
end
------------------------------------------------------------------
Can you tell me also how you prevent:
- Infinite while do (i know user should use it with care but why increase risk?)
- that user do not write SUSPEND/YIELD/FETCH or user call it to many times?
- minimize code execution like in avg? Instead of make one division you propose
design where you must divide it always row by row.
And e.g. if you have 1000 rows with only one grouping key, you have 1000 of
additions and 1000 of divisions.
------------------------------------------------------------------
How work internal SUM, AVG already? They call yead/fetch/suspend or something
like this?
Or engine send them required state of parameters/variables?
regards,
Karol Bieniaszewski
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