50 lines
785 B
Markdown
50 lines
785 B
Markdown
# 列式存储
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用于分析查询和聚合的面向列的存储。
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## 用法
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```nim
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import barabadb/core/columnar
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var batch = newColumnBatch()
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var ageCol = batch.addInt64Col("age")
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var nameCol = batch.addStringCol("name")
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ageCol.appendInt64(25)
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nameCol.appendString("Alice")
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```
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## 聚合
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```nim
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echo ageCol.sumInt64()
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echo ageCol.avgInt64()
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echo ageCol.minInt64()
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echo ageCol.maxInt64()
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```
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## 编码
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### RLE
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```nim
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let rle = rleEncode(@[1'i64, 1, 1, 2, 2, 3])
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```
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### Dictionary
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```nim
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let dict = dictEncode(@["apple", "banana", "apple"])
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```
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## 列类型
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| 类型 | 描述 |
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|------|------|
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| `int32` | 32 位整数 |
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| `int64` | 64 位整数 |
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| `float32` | 32 位浮点数 |
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| `float64` | 64 位浮点数 |
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| `string` | 可变长度字符串 |
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| `bool` | 布尔值 | |