common_function/scalars/
uddsketch_calc.rs

1// Copyright 2023 Greptime Team
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15//! Implementation of the scalar function `uddsketch_calc`.
16
17use std::fmt;
18use std::fmt::Display;
19
20use common_query::error::{DowncastVectorSnafu, InvalidFuncArgsSnafu, Result};
21use common_query::prelude::{Signature, Volatility};
22use datatypes::data_type::ConcreteDataType;
23use datatypes::prelude::Vector;
24use datatypes::scalars::{ScalarVector, ScalarVectorBuilder};
25use datatypes::vectors::{BinaryVector, Float64VectorBuilder, MutableVector, VectorRef};
26use snafu::OptionExt;
27use uddsketch::UDDSketch;
28
29use crate::function::{Function, FunctionContext};
30use crate::function_registry::FunctionRegistry;
31
32const NAME: &str = "uddsketch_calc";
33
34/// UddSketchCalcFunction implements the scalar function `uddsketch_calc`.
35///
36/// It accepts two arguments:
37/// 1. A percentile (as f64) for which to compute the estimated quantile (e.g. 0.95 for p95).
38/// 2. The serialized UDDSketch state, as produced by the aggregator (binary).
39///
40/// For each row, it deserializes the sketch and returns the computed quantile value.
41#[derive(Debug, Default)]
42pub struct UddSketchCalcFunction;
43
44impl UddSketchCalcFunction {
45    pub fn register(registry: &FunctionRegistry) {
46        registry.register_scalar(UddSketchCalcFunction);
47    }
48}
49
50impl Display for UddSketchCalcFunction {
51    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
52        write!(f, "{}", NAME.to_ascii_uppercase())
53    }
54}
55
56impl Function for UddSketchCalcFunction {
57    fn name(&self) -> &str {
58        NAME
59    }
60
61    fn return_type(&self, _input_types: &[ConcreteDataType]) -> Result<ConcreteDataType> {
62        Ok(ConcreteDataType::float64_datatype())
63    }
64
65    fn signature(&self) -> Signature {
66        // First argument: percentile (float64)
67        // Second argument: UDDSketch state (binary)
68        Signature::exact(
69            vec![
70                ConcreteDataType::float64_datatype(),
71                ConcreteDataType::binary_datatype(),
72            ],
73            Volatility::Immutable,
74        )
75    }
76
77    fn eval(&self, _func_ctx: &FunctionContext, columns: &[VectorRef]) -> Result<VectorRef> {
78        if columns.len() != 2 {
79            return InvalidFuncArgsSnafu {
80                err_msg: format!("uddsketch_calc expects 2 arguments, got {}", columns.len()),
81            }
82            .fail();
83        }
84
85        let perc_vec = &columns[0];
86        let sketch_vec = columns[1]
87            .as_any()
88            .downcast_ref::<BinaryVector>()
89            .with_context(|| DowncastVectorSnafu {
90                err_msg: format!("expect BinaryVector, got {}", columns[1].vector_type_name()),
91            })?;
92        let len = sketch_vec.len();
93        let mut builder = Float64VectorBuilder::with_capacity(len);
94
95        for i in 0..len {
96            let perc_opt = perc_vec.get(i).as_f64_lossy();
97            let sketch_opt = sketch_vec.get_data(i);
98
99            if sketch_opt.is_none() || perc_opt.is_none() {
100                builder.push_null();
101                continue;
102            }
103
104            let sketch_bytes = sketch_opt.unwrap();
105            let perc = perc_opt.unwrap();
106
107            // Deserialize the UDDSketch from its bincode representation
108            let sketch: UDDSketch = match bincode::deserialize(sketch_bytes) {
109                Ok(s) => s,
110                Err(e) => {
111                    common_telemetry::trace!("Failed to deserialize UDDSketch: {}", e);
112                    builder.push_null();
113                    continue;
114                }
115            };
116
117            // Check if the sketch is empty, if so, return null
118            // This is important to avoid panics when calling estimate_quantile on an empty sketch
119            // In practice, this will happen if input is all null
120            if sketch.bucket_iter().count() == 0 {
121                builder.push_null();
122                continue;
123            }
124            // Compute the estimated quantile from the sketch
125            let result = sketch.estimate_quantile(perc);
126            builder.push(Some(result));
127        }
128
129        Ok(builder.to_vector())
130    }
131}
132
133#[cfg(test)]
134mod tests {
135    use std::sync::Arc;
136
137    use datatypes::vectors::{BinaryVector, Float64Vector};
138
139    use super::*;
140
141    #[test]
142    fn test_uddsketch_calc_function() {
143        let function = UddSketchCalcFunction;
144        assert_eq!("uddsketch_calc", function.name());
145        assert_eq!(
146            ConcreteDataType::float64_datatype(),
147            function
148                .return_type(&[ConcreteDataType::float64_datatype()])
149                .unwrap()
150        );
151
152        // Create a test sketch
153        let mut sketch = UDDSketch::new(128, 0.01);
154        sketch.add_value(10.0);
155        sketch.add_value(20.0);
156        sketch.add_value(30.0);
157        sketch.add_value(40.0);
158        sketch.add_value(50.0);
159        sketch.add_value(60.0);
160        sketch.add_value(70.0);
161        sketch.add_value(80.0);
162        sketch.add_value(90.0);
163        sketch.add_value(100.0);
164
165        // Get expected values directly from the sketch
166        let expected_p50 = sketch.estimate_quantile(0.5);
167        let expected_p90 = sketch.estimate_quantile(0.9);
168        let expected_p95 = sketch.estimate_quantile(0.95);
169
170        let serialized = bincode::serialize(&sketch).unwrap();
171        let percentiles = vec![0.5, 0.9, 0.95];
172
173        let args: Vec<VectorRef> = vec![
174            Arc::new(Float64Vector::from_vec(percentiles.clone())),
175            Arc::new(BinaryVector::from(vec![Some(serialized.clone()); 3])),
176        ];
177
178        let result = function.eval(&FunctionContext::default(), &args).unwrap();
179        assert_eq!(result.len(), 3);
180
181        // Test median (p50)
182        assert!(
183            matches!(result.get(0), datatypes::value::Value::Float64(v) if (v - expected_p50).abs() < 1e-10)
184        );
185        // Test p90
186        assert!(
187            matches!(result.get(1), datatypes::value::Value::Float64(v) if (v - expected_p90).abs() < 1e-10)
188        );
189        // Test p95
190        assert!(
191            matches!(result.get(2), datatypes::value::Value::Float64(v) if (v - expected_p95).abs() < 1e-10)
192        );
193    }
194
195    #[test]
196    fn test_uddsketch_calc_function_errors() {
197        let function = UddSketchCalcFunction;
198
199        // Test with invalid number of arguments
200        let args: Vec<VectorRef> = vec![Arc::new(Float64Vector::from_vec(vec![0.95]))];
201        let result = function.eval(&FunctionContext::default(), &args);
202        assert!(result.is_err());
203        assert!(result
204            .unwrap_err()
205            .to_string()
206            .contains("uddsketch_calc expects 2 arguments"));
207
208        // Test with invalid binary data
209        let args: Vec<VectorRef> = vec![
210            Arc::new(Float64Vector::from_vec(vec![0.95])),
211            Arc::new(BinaryVector::from(vec![Some(vec![1, 2, 3])])), // Invalid binary data
212        ];
213        let result = function.eval(&FunctionContext::default(), &args).unwrap();
214        assert_eq!(result.len(), 1);
215        assert!(matches!(result.get(0), datatypes::value::Value::Null));
216    }
217}
common_function/scalars/uddsketch_calc.rs

common_function/scalars/
uddsketch_calc.rs
