实际样品与填充样品之间的差异

Question

我希望具有GROUP BY time intervals and fill(previous)的子查询的行为与所得数据集相同。但是针对子查询的查询返回意外结果。

环境

InfluxDB v1.6.3

发生了什么

这是一个示例数据集：

# DDL
CREATE DATABASE myapp

# DML
# CONTEXT-DATABASE: myapp
reqcnt,endpoint=a value=1 1563361000000000000
reqcnt,endpoint=b value=1 1563361000000000000
reqcnt,endpoint=a value=2 1563361005000000000
reqcnt,endpoint=b value=2 1563361005000000000
reqcnt,endpoint=a value=3 1563361010000000000
reqcnt,endpoint=b value=3 1563361010000000000

您可以通过执行以下操作导入以上数据：

$ influx -import /path/to/dataset -precision ns

数据很简单：每个端点三个值，每5秒测量一次。但是因为我想要一个具有每秒值的数据集，所以我做了一个子查询，用先前的值填充缺失的值：

> SELECT LAST(value) AS lv FROM reqcnt WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s), endpoint fill(previous)
name: reqcnt
tags: endpoint=a
time                lv
----                --
1563361000000000000 1
1563361001000000000 1
1563361002000000000 1
1563361003000000000 1
1563361004000000000 1
1563361005000000000 2
1563361006000000000 2
1563361007000000000 2
1563361008000000000 2
1563361009000000000 2
1563361010000000000 3

name: reqcnt
tags: endpoint=b
time                lv
----                --
1563361000000000000 1
1563361001000000000 1
1563361002000000000 1
1563361003000000000 1
1563361004000000000 1
1563361005000000000 2
1563361006000000000 2
1563361007000000000 2
1563361008000000000 2
1563361009000000000 2
1563361010000000000 3

到目前为止，一切都很好。现在，我想总结一下端点：

> SELECT SUM(value) FROM (SELECT LAST(value) AS value FROM reqcnt WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s), endpoint fill(previous)) WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s)
name: reqcnt
time                sum
----                ---
1563361000000000000 1
1563361001000000000 1
1563361002000000000 1
1563361003000000000 1
1563361004000000000 1
1563361005000000000 1
1563361006000000000 1
1563361007000000000 1
1563361008000000000 1
1563361009000000000 1
1563361010000000000 1
1563361000000000000 1
1563361001000000000 1
1563361002000000000 1
1563361003000000000 1
1563361004000000000 1
1563361005000000000 1
1563361006000000000 1
1563361007000000000 1
1563361008000000000 1
1563361009000000000 1
1563361010000000000 1
1563361005000000000 2
1563361006000000000 2
1563361007000000000 2
1563361008000000000 2
1563361009000000000 2
1563361010000000000 2
1563361005000000000 2
1563361006000000000 2
1563361007000000000 2
1563361008000000000 2
1563361009000000000 2
1563361010000000000 8

为什么结果包含相同时间戳的多个值？当我将11加11时为什么是34个值？

我期望的

> SELECT SUM(value) FROM (SELECT LAST(value) AS value FROM reqcnt WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s), endpoint fill(previous)) WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s)
name: reqcnt
time                sum
----                ---
1563361000000000000 2
1563361001000000000 2
1563361002000000000 2
1563361003000000000 2
1563361004000000000 2
1563361005000000000 2
1563361006000000000 4
1563361007000000000 4
1563361008000000000 4
1563361009000000000 4
1563361010000000000 6

创建每秒的数据集并对其进行查询将返回预期结果：

# DDL
CREATE DATABASE myapp

# DML
# CONTEXT-DATABASE: myapp
reqcnt2,endpoint=a value=1 1563361000000000000
reqcnt2,endpoint=b value=1 1563361000000000000
reqcnt2,endpoint=a value=1 1563361001000000000
reqcnt2,endpoint=b value=1 1563361001000000000
reqcnt2,endpoint=a value=1 1563361002000000000
reqcnt2,endpoint=b value=1 1563361002000000000
reqcnt2,endpoint=a value=1 1563361003000000000
reqcnt2,endpoint=b value=1 1563361003000000000
reqcnt2,endpoint=a value=1 1563361004000000000
reqcnt2,endpoint=b value=1 1563361004000000000
reqcnt2,endpoint=a value=2 1563361005000000000
reqcnt2,endpoint=a value=2 1563361005000000000
reqcnt2,endpoint=b value=2 1563361006000000000
reqcnt2,endpoint=a value=2 1563361006000000000
reqcnt2,endpoint=b value=2 1563361007000000000
reqcnt2,endpoint=a value=2 1563361007000000000
reqcnt2,endpoint=b value=2 1563361008000000000
reqcnt2,endpoint=a value=2 1563361008000000000
reqcnt2,endpoint=b value=2 1563361009000000000
reqcnt2,endpoint=a value=2 1563361009000000000
reqcnt2,endpoint=a value=3 1563361010000000000
reqcnt2,endpoint=b value=3 1563361010000000000

导入以上内容并查询数据集将显示预期结果：

> SELECT SUM(value) FROM reqcnt2 WHERE time >= 1563361000000000000 AND time <= 1563361010000000000 GROUP BY time(1s)

name: reqcnt2
time                sum
----                ---
1563361000000000000 2
1563361001000000000 2
1563361002000000000 2
1563361003000000000 2
1563361004000000000 2
1563361005000000000 2
1563361006000000000 4
1563361007000000000 4
1563361008000000000 4
1563361009000000000 4
1563361010000000000 6

那有什么区别？不应像查询实际数据集一样查询已填充的数据集？有没有适当的方法来查询此类子查询？