如何使用 jq 获得每个组和子组的最大值

Question

jq 是一个很棒的工具，它可以做很多事情。作为输入我有

[
  {
    "backup": [
      {
        "timestamp": { "start": 1642144383, "stop": 1642144386 },
        "info": {  "size": 1200934840},
        "type": "full"
      },
      {
        "timestamp": {"start": 1642144388, "stop":  1642144392 },
        "info": { "size": 1168586300
        },
        "type": "incr"
      },
      {
        "timestamp": {"start": 1642145388, "stop":  1642145392 },
        "info": { "size": 1168586330
        },
        "type": "incr"
      }
    ],
    "name": "dbname1"
  },
  {
    "backup": [
      {
        "timestamp": { "start": 1642144383, "stop": 1642144386 },
        "info": {  "size": 1200934840},
        "type": "full"
      },
      {
        "timestamp": {"start": 1642144388, "stop":  1642144392 },
        "info": { "size": 1168586300
        },
        "type": "incr"
      }
    ],
    "name": "dbname2"
  }
]

并使用

jq 'map([.backup[] + {name}] | max_by(.timestamp.stop))'

我得到了最新的 timestamp.stop 名字。我应该如何更改它以获得名称和组的最新 timestamp.stop？在 SQL 这将类似于 max(.timestamp.stop) group by .name,.type 希望输出像：

[
  {
    "timestamp": {
      "start": 1642144383,
      "stop": 1642144386
    },
    "info": {
      "size": 1200934840
    },
    "type": "full",
    "name": "dbname1"
  },
  {
    "timestamp": {
      "start": 1642145388,
      "stop": 1642145392
    },
    "info": {
      "size": 1168586330
    },
    "type": "incr",
    "name": "dbname1"
  },
  {
    "timestamp": {
      "start": 1642144383,
      "stop": 1642144386
    },
    "info": {
      "size": 1200934840
    },
    "type": "full",
    "name": "dbname2"
  },
  {
    "timestamp": {
      "start": 1642144388,
      "stop": 1642144392
    },
    "info": {
      "size": 1168586300
    },
    "type": "incr",
    "name": "dbname2"
  }
]

Answer 1

删除内部括号以展平数组，然后 group_by 两个条件（这使您的条件成为一个数组），map 您的 max_by 到结果数组：

jq 'map(.backup[] + {name}) | group_by([.name, .type]) | map(max_by(.timestamp.stop))'

[
  {
    "timestamp": {
      "start": 1642144383,
      "stop": 1642144386
    },
    "info": {
      "size": 1200934840
    },
    "type": "full",
    "name": "dbname1"
  },
  {
    "timestamp": {
      "start": 1642145388,
      "stop": 1642145392
    },
    "info": {
      "size": 1168586330
    },
    "type": "incr",
    "name": "dbname1"
  },
  {
    "timestamp": {
      "start": 1642144383,
      "stop": 1642144386
    },
    "info": {
      "size": 1200934840
    },
    "type": "full",
    "name": "dbname2"
  },
  {
    "timestamp": {
      "start": 1642144388,
      "stop": 1642144392
    },
    "info": {
      "size": 1168586300
    },
    "type": "incr",
    "name": "dbname2"
  }
]

Demo

Answer 2

这似乎产生了所需的预期输出。在执行 max_by

之前，您需要按 .type 记录进行额外分组

map( .backup[] + {name} ) | group_by(.name)[] | 
  group_by(.type) | map(max_by(.timestamp.stop))

jqplay demo

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