imay commented on a change in pull request #1432: Add percentile_approx
aggregate function
URL: https://github.com/apache/incubator-doris/pull/1432#discussion_r302101549
##########
File path: be/src/exprs/aggregate_functions.cpp
##########
@@ -231,6 +232,81 @@ void AggregateFunctions::avg_update(FunctionContext* ctx,
const T& src, StringVa
++avg->count;
}
+struct PercentileApproxState {
+public:
+ PercentileApproxState() {
+ digest = new TDigest();
+ }
+ ~PercentileApproxState() {
+ delete digest;
+ }
+
+ TDigest *digest = nullptr;
+ double targetQuantile = -1.0;
+};
+
+void AggregateFunctions::percentile_approx_init(FunctionContext* ctx,
StringVal* dst) {
+ dst->is_null = false;
+ dst->len = sizeof(PercentileApproxState);
+ dst->ptr = (uint8_t*) new PercentileApproxState();
+};
+
+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;
+}
+
+StringVal AggregateFunctions::percentile_approx_serialize(FunctionContext*
ctx, const StringVal& src) {
+ DCHECK(!src.is_null);
+
+ PercentileApproxState *percentile =
reinterpret_cast<PercentileApproxState*>(src.ptr);
+ uint32_t serialized_size = percentile->digest->serialized_size();
+ StringVal result(ctx, sizeof(double) + serialized_size);
+ memcpy(result.ptr, &percentile->targetQuantile, sizeof(double));
+ percentile->digest->serialize(result.ptr + sizeof(double));
+
+ delete percentile;
+ return result;
+}
+
+void AggregateFunctions::percentile_approx_merge(FunctionContext* ctx, const
StringVal& src, StringVal* dst) {
+ DCHECK(dst->ptr != NULL);
+ DCHECK_EQ(sizeof(PercentileApproxState), dst->len);
+
+ double quantile;
+ memcpy(&quantile, src.ptr, sizeof(double));
+
+ PercentileApproxState *src_percentile = new PercentileApproxState();
+ src_percentile->targetQuantile = quantile;
+ src_percentile->digest = new TDigest();
Review comment:
no need to new another TDigest, this will lead to memory leak
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