为什么更改maxResults会导致Google / Gmail中的结果总数发生变化？

Question

为什么更改maxResults参数会导致resultSizeEstimate在调用gmail.users.messages.list()时发生剧烈变化

Google文档将resultSizeEstimate列表为:估计结果总数。

..。这意味着这个最终的结果集不应该仅仅通过改变每页返回的项目数而改变。

maxResults: 1 示例A: .

{
  "config": {
    "url": "https://www.googleapis.com/gmail/v1/users/me/messages?q=before%3A2021%2F1%2F9&maxResults=1",
    "method": "GET",
    "headers": {
      "Accept-Encoding": "gzip",
      "User-Agent": "google-api-nodejs-client/0.7.2 (gzip)",
      "Authorization": "Bearer [snip]",
      "Accept": "application/json"
    },
    "params": {
      "q": "before:2021/1/9",
      "maxResults": 1
    },
    "responseType": "json"
  },
  "data": {
    "messages": [ ... ],
    "nextPageToken": "14911817971227869758",
    "resultSizeEstimate": 8
  },
  "headers": {
    "alt-svc": "h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000,h3-Q050=\":443\"; ma=2592000,h3-Q046=\":443\"; ma=2592000,h3-Q043=\":443\"; ma=2592000,quic=\":443\"; ma=2592000; v=\"46,43\"",
    "cache-control": "private",
    "connection": "close",
    "content-encoding": "gzip",
    "content-type": "application/json; charset=UTF-8",
    "date": "Sun, 09 Jan 2022 12:59:48 GMT",
    "server": "ESF",
    "transfer-encoding": "chunked",
    "vary": "Origin, X-Origin, Referer",
    "x-content-type-options": "nosniff",
    "x-frame-options": "SAMEORIGIN",
    "x-xss-protection": "0"
  },
  "status": 200,
  "statusText": "OK"
}

maxResults: 2 示例B: .

{
  "config": {
    "url": "https://www.googleapis.com/gmail/v1/users/me/messages?q=before%3A2021%2F1%2F9&maxResults=2",
    "method": "GET",
    "headers": {
      "Accept-Encoding": "gzip",
      "User-Agent": "google-api-nodejs-client/0.7.2 (gzip)",
      "Authorization": "Bearer [snip]",
      "Accept": "application/json"
    },
    "params": {
      "q": "before:2021/1/9",
      "maxResults": 2
    },
    "responseType": "json"
  },
  "data": {
    "messages": [ ... ],
    "nextPageToken": "16903415066875011466",
    "resultSizeEstimate": 12
  },
  "headers": {
    "alt-svc": "h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000,h3-Q050=\":443\"; ma=2592000,h3-Q046=\":443\"; ma=2592000,h3-Q043=\":443\"; ma=2592000,quic=\":443\"; ma=2592000; v=\"46,43\"",
    "cache-control": "private",
    "connection": "close",
    "content-encoding": "gzip",
    "content-type": "application/json; charset=UTF-8",
    "date": "Sun, 09 Jan 2022 13:10:48 GMT",
    "server": "ESF",
    "transfer-encoding": "chunked",
    "vary": "Origin, X-Origin, Referer",
    "x-content-type-options": "nosniff",
    "x-frame-options": "SAMEORIGIN",
    "x-xss-protection": "0"
  },
  "status": 200,
  "statusText": "OK"
}

maxResults: (not set)示例C: .

{
  "config": {
    "url": "https://www.googleapis.com/gmail/v1/users/me/messages?q=before%3A2021%2F1%2F9",
    "method": "GET",
    "headers": {
      "Accept-Encoding": "gzip",
      "User-Agent": "google-api-nodejs-client/0.7.2 (gzip)",
      "Authorization": "Bearer [snip]",
      "Accept": "application/json"
    },
    "params": {
      "q": "before:2021/1/9"
    },
    "responseType": "json"
  },
  "data": {
    "messages": [ ... ],
    "nextPageToken": "16942818266524948378",
    "resultSizeEstimate": 412
  },
  "headers": {
    "alt-svc": "h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000,h3-Q050=\":443\"; ma=2592000,h3-Q046=\":443\"; ma=2592000,h3-Q043=\":443\"; ma=2592000,quic=\":443\"; ma=2592000; v=\"46,43\"",
    "cache-control": "private",
    "connection": "close",
    "content-encoding": "gzip",
    "content-type": "application/json; charset=UTF-8",
    "date": "Sun, 09 Jan 2022 13:09:05 GMT",
    "server": "ESF",
    "transfer-encoding": "chunked",
    "vary": "Origin, X-Origin, Referer",
    "x-content-type-options": "nosniff",
    "x-frame-options": "SAMEORIGIN",
    "x-xss-protection": "0"
  },
  "status": 200,
  "statusText": "OK"
}

Answer 1

此前曾在“问题跟踪器”中报道过这一点，谷歌认为这是有意的行为，因为人们预计resultSizeEstimate并不准确；这是一个“估计”：

resultSizeEstimate显示不同值的原因在于它的估计。正如在resultSizeEstimate中提到的，文档只是估计结果的总数，而不是结果的确切数量。

参考资料：

• users.messages.list方法在使用“maxResults”参数时返回不同数量的消息