中文

Introduction

Generally, we need to establish data indexes to speed up data retrieval in the following two situations:

• Build indexes to optimize data retrieval in some database.
• Build indexes to optimize constraints matching in some strategy engine, advertising engine, experimental platform engine and so on.

This project is working in the second situation.

Database indexes are mainly to be used to accelerate data point search, and can be constructed based on B-Tree, B+Tree, R-Tree, KD-Tree, Radix-Tree, HashTree or other data structures. The basic principle of these data point tree indexes is to narrow the query scope by designing decomposition hyperplanes.

Constraint retrieval can also speed up retrieval by cutting the plane, but it requires some special processing. This project optimized the algorithm for selecting the cutting plane and achieved good results.

Performance

Select 10 in 10-dimensional discrete space

there are 100 optional values per discrete space

Number of constraints to be queried	QPS without index	QPS with index	speedup
100	80998	485201	6
1000	7767	427899	55
10000	704	239578	340
100000	25	201207	8140

Select 5 in 5-dimensional numerical space

Number of constraints to be queried	QPS without index	QPS with index	speedup
100	93110	270197	3
1000	8904	162522	18
10000	863	90926	105
100000	43	49111	1153

Select 3 for 5-dimensional numerical space and 5 for 20-dimensional discrete space

Number of constraints to be queried	QPS without index	QPS with index	speedup
100	69842	173792	2
1000	6313	88660	14
10000	482	43420	90
100000	17	24226	1399

Example

// build a new tree
tree1 := NewTree(DimTypes{
	"Field1": DimTypeDiscrete, // discrete space
	"Field2": DimTypeReal, // real space
}, &TreeOptions{
	TreeLevelMax:                16, // tree's max height
	LeafNodeDataMax:                 4, // max data number within leaf node
	BranchingDecreasePercentMin: 0.1, // min split ratio
})

err := tree1.Add(Rect{
	"Field1": Measures{MeasureString("one"), MeasureString("two"), MeasureString("three")}, // targeting discrete string 
	"Field2": Interval{MeasureFloat(0.1), MeasureFloat(2.0)}}, // target real interval
	"target1")
if err != nil {
	log.Fatal("node add error:", err)
}
tree1.Build() // build tree

// search point
result := tree1.Search(Point{"Field1": MeasureString("one"), "Field2": MeasureFloat(0.3)})

if len(result) != 1 || result[0].(string) != "target1" {
	log.Fatal("tree search error")
}