imay commented on a change in pull request #1432: Add percentile_approx
aggregate function
URL: https://github.com/apache/incubator-doris/pull/1432#discussion_r301529949
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File path: be/src/exprs/aggregate_functions.cpp
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@@ -231,6 +232,84 @@ void AggregateFunctions::avg_update(FunctionContext* ctx,
const T& src, StringVa
++avg->count;
}
+struct PercentileApproxState {
+public:
+ TDigest *digest = nullptr;
+ double targetQuantile = -1.0;
+
+ ~PercentileApproxState() {
+ if (digest != nullptr) {
+ delete digest;
+ }
+ }
+};
+
+void AggregateFunctions::percentile_approx_init(FunctionContext* ctx,
StringVal* dst) {
+ dst->is_null = false;
+ dst->len = sizeof(PercentileApproxState);
+ dst->ptr = (uint8_t*) new PercentileApproxState();
+
+ PercentileApproxState* percentile =
reinterpret_cast<PercentileApproxState*>(dst->ptr);
+ percentile->targetQuantile = -1.0;
+ percentile->digest = new TDigest();
+};
+
+template<typename T>
+void AggregateFunctions::percentile_approx_update(FunctionContext* ctx, const
T& src, const DoubleVal& quantile, StringVal* dst) {
+ if (src.is_null) {
+ return;
+ }
+ DCHECK(dst->ptr != NULL);
+ DCHECK_EQ(sizeof(PercentileApproxState), dst->len);
+
+ PercentileApproxState* percentile =
reinterpret_cast<PercentileApproxState*>(dst->ptr);
+ percentile->digest->add(src.val);
+ percentile->targetQuantile = quantile.val;
Review comment:
I think you should check quantile in Frontend which should be a const
expression. If quantile is not const, I think this function has no use.
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