HappenLee commented on code in PR #67805:
URL: https://github.com/apache/doris/pull/67805#discussion_r3980249349
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be/src/exprs/aggregate/aggregate_function_ema.h:
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@@ -86,12 +87,17 @@ struct ExponentialMovingAverageData {
}
void merge(const ExponentialMovingAverageData& rhs) {
- double hd = half_decay != 0.0 ? half_decay : rhs.half_decay;
- if (hd == 0.0) {
+ if (rhs.half_decay == 0.0) {
Review Comment:
After discussing the intended contract, we will preserve the existing
zero-half-decay behavior: zero returns 0 and serves as the
empty/non-contributing state marker. A serialized zero-half-decay state is
intentionally ignored by `_merge`/`_union`, even if it was built from non-null
rows. Thus 0 versus a nonzero half-decay does not raise a mismatch; the
compatibility check applies to contributing states with nonzero half-decays.
I have documented this exception in the function's source comment and a
local documentation note, and withdrawn the proposed NaN-sentinel
implementation. This is a clarification of the intended contract rather than a
change to distinguish an initialized zero configuration. The separate
NaN-equality concern remains open for discussion.
The documentation-only change passed formatting, header-hygiene, and
whitespace checks. Runtime tests were not rerun. All changes remain local; no
code has been pushed.
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