如何处理包含 json/array 数据的 postgres 文本列答案

【问题标题】：How to deal with a postgres text column that holds json/array data如何处理包含 json/array 数据的 postgres 文本列
【发布时间】：2023-03-18 02:05:01
【问题描述】：

我有一个保存车辆数据的 postgres（版本 11）表。数据从 CSV 文件中填充。名为 mot_history 的字段之一是文本字段，有时为 NULL 或具有“没有可用的 MOT 数据”的值，但通常如下所示：

[{"completedDate": "2019-05-08T13:38:21+00:00", "expiryDate": "2020-11-07T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 89178}, "passed": true, "rfcAndComments": [{"text": "Nearside Non obligatory mirror damaged ()", "type": "ADVISORY"}]}, {"completedDate": "2019-04-29T08:39:45+00:00", "expiryDate": null, "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 88909}, "passed": false, "rfcAndComments": [{"text": "Nearside Front Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Offside Front Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Nearside Rear Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Nearside Obligatory mirror seriously damaged, affecting the rear view (3.3 (b) (ii))", "type": "FAIL"}]}, {"completedDate": "2018-05-01T14:33:15+00:00", "expiryDate": "2019-04-30T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 77880}, "passed": true, "rfcAndComments": [{"text": "Nearside Obligatory mirror damaged, but not seriously affecting the rear view (8.1.2a)", "type": "ADVISORY"}, {"text": "Offside Rear  jacking  point  missing", "type": "ADVISORY"}]}, {"completedDate": "2017-04-26T08:41:07+00:00", "expiryDate": "2018-04-26T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 66658}, "passed": true, "rfcAndComments": [{"text": "Nearside Non obligatory mirror damaged ()", "type": "ADVISORY"}, {"text": "Windscreen has damage to an area less than a 40mm circle outside zone 'A' (8.3.1d)", "type": "ADVISORY"}]}, {"completedDate": "2016-04-27T09:46:44+00:00", "expiryDate": "2017-04-26T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 54490}, "passed": true, "rfcAndComments": [{"text": "Nearside Obligatory mirror damaged, but not seriously affecting the rear view (8.1.2a)", "type": "ADVISORY"}, {"text": "Front brake disc worn, pitted or scored, but not seriously weakened (3.5.1i)", "type": "ADVISORY"}, {"text": "brake warning lamp illuminated", "type": "ADVISORY"}]}, {"completedDate": "2015-04-20T10:45:28+00:00", "expiryDate": "2016-04-19T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 42143}, "passed": true, "rfcAndComments": [{"text": "Windscreen has damage to an area less than a 10mm circle within zone 'A' (8.3.1a)", "type": "ADVISORY"}, {"text": "nearside obligatory mirror seriously damaged, affecting the rear view", "type": "USER ENTERED"}, {"text": "parking brake noisy on application", "type": "USER ENTERED"}]}, {"completedDate": "2015-04-15T12:42:31+00:00", "expiryDate": null, "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 41921}, "passed": false, "rfcAndComments": [{"text": "Nearside Inner Front Brake pad(s) less than 1.5 mm thick (3.5.1g)", "type": "FAIL"}, {"text": "Nearside Inner Rear Brake pad(s) less than 1.5 mm thick (3.5.1g)", "type": "FAIL"}, {"text": "Windscreen has damage to an area less than a 10mm circle within zone 'A' (8.3.1a)", "type": "ADVISORY"}, {"text": "nearside obligatory mirror seriously damaged, affecting the rear view", "type": "USER ENTERED"}, {"text": "parking brake noisy on application", "type": "USER ENTERED"}]}, {"completedDate": "2014-04-09T17:17:55+00:00", "expiryDate": "2015-04-08T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 29857}, "passed": true, "rfcAndComments": [{"text": "Rear Tyre worn close to the legal limit (4.1.E.1)", "type": "ADVISORY"}, {"text": "both front tyres worn on inner edges", "type": "USER ENTERED"}]}]
[{"completedDate": "2017-06-22T07:40:58+00:00", "expiryDate": "2018-07-01T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 23985}, "passed": true, "rfcAndComments": []}]
[{"completedDate": "2020-03-05T12:11:13+00:00", "expiryDate": "2021-03-25T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 58804}, "passed": true, "rfcAndComments": []}, {"completedDate": "2019-03-26T13:56:21+00:00", "expiryDate": "2020-03-25T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 53674}, "passed": true, "rfcAndComments": []}, {"completedDate": "2018-10-27T10:39:06+00:00", "expiryDate": "2019-10-29T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 52580}, "passed": true, "rfcAndComments": [{"text": "Rear Brake pad(s) wearing thin  1.5 mm (1.1.13 (a) (ii))", "type": "ADVISORY"}, {"text": "Nearside Front Tyre slightly damaged/cracking or perishing  Tyre cracking. (5.2.3 (d) (ii))", "type": "ADVISORY"}, {"text": "Offside Front Tyre slightly damaged/cracking or perishing  Tyre cracking. (5.2.3 (d) (ii))", "type": "ADVISORY"}, {"text": "Nearside Front Tyre worn close to legal limit/worn on edge  2.5 mm (5.2.3 (e))", "type": "ADVISORY"}, {"text": "Offside Front Tyre worn close to legal limit/worn on edge  2.9 mm (5.2.3 (e))", "type": "ADVISORY"}, {"text": "Nearside Front Outer Tyre worn close to legal limit/worn on edge  Worn outer edge. (5.2.3 (e))", "type": "ADVISORY"}]}]

上面的格式稍微多一点，让您更好地了解结构是什么

[
    {"completedDate": "2019-05-08T13:38:21+00:00", "expiryDate": "2020-11-07T00:00:00+00:00", "testNumber": 9999999999, "odomoter": {"unit": "mi", "value": 89178}, "passed": true, "rfcAndComments": 
        [
            {"text": "Nearside Non obligatory mirror damaged ()", "type": "ADVISORY"}
        ]
    }, 
    {"completedDate": "2019-04-29T08:39:45+00:00", "expiryDate": null, "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 88909}, "passed": false, "rfcAndComments": [{"text": "Nearside Front Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Offside Front Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Nearside Rear Tyre has a cut in excess of the requirements deep enough to reach the ply or cords (5.2.3 (d) (i))", "type": "FAIL"}, {"text": "Nearside Obligatory mirror seriously damaged, affecting the rear view (3.3 (b) (ii))", "type": "FAIL"}]}, 
    {"completedDate": "2018-05-01T14:33:15+00:00", "expiryDate": "2019-04-30T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 77880}, "passed": true, "rfcAndComments": [{"text": "Nearside Obligatory mirror damaged, but not seriously affecting the rear view (8.1.2a)", "type": "ADVISORY"}, {"text": "Offside Rear  jacking  point  missing", "type": "ADVISORY"}]}, 
    {"completedDate": "2017-04-26T08:41:07+00:00", "expiryDate": "2018-04-26T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 66658}, "passed": true, "rfcAndComments": [{"text": "Nearside Non obligatory mirror damaged ()", "type": "ADVISORY"}, {"text": "Windscreen has damage to an area less than a 40mm circle outside zone 'A' (8.3.1d)", "type": "ADVISORY"}]}, 
    {"completedDate": "2016-04-27T09:46:44+00:00", "expiryDate": "2017-04-26T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 54490}, "passed": true, "rfcAndComments": [{"text": "Nearside Obligatory mirror damaged, but not seriously affecting the rear view (8.1.2a)", "type": "ADVISORY"}, {"text": "Front brake disc worn, pitted or scored, but not seriously weakened (3.5.1i)", "type": "ADVISORY"}, {"text": "brake warning lamp illuminated", "type": "ADVISORY"}]}, 
    {"completedDate": "2015-04-20T10:45:28+00:00", "expiryDate": "2016-04-19T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 42143}, "passed": true, "rfcAndComments": [{"text": "Windscreen has damage to an area less than a 10mm circle within zone 'A' (8.3.1a)", "type": "ADVISORY"}, {"text": "nearside obligatory mirror seriously damaged, affecting the rear view", "type": "USER ENTERED"}, {"text": "parking brake noisy on application", "type": "USER ENTERED"}]}, 
    {"completedDate": "2015-04-15T12:42:31+00:00", "expiryDate": null, "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 41921}, "passed": false, "rfcAndComments": [{"text": "Nearside Inner Front Brake pad(s) less than 1.5 mm thick (3.5.1g)", "type": "FAIL"}, {"text": "Nearside Inner Rear Brake pad(s) less than 1.5 mm thick (3.5.1g)", "type": "FAIL"}, {"text": "Windscreen has damage to an area less than a 10mm circle within zone 'A' (8.3.1a)", "type": "ADVISORY"}, {"text": "nearside obligatory mirror seriously damaged, affecting the rear view", "type": "USER ENTERED"}, {"text": "parking brake noisy on application", "type": "USER ENTERED"}]}, 
    {"completedDate": "2014-04-09T17:17:55+00:00", "expiryDate": "2015-04-08T00:00:00+00:00", "testNumber": 999999999, "odomoter": {"unit": "mi", "value": 29857}, "passed": true, "rfcAndComments": [{"text": "Rear Tyre worn close to the legal limit (4.1.E.1)", "type": "ADVISORY"}, {"text": "both front tyres worn on inner edges", "type": "USER ENTERED"}]}
]

我无法控制外部输入数据的格式，但我想知道是否可以使用 SQL 来获取存储在这个 JSON/array 类结构中的值。例如，假设我想返回已通过 MOT 的车辆的到期日期。我知道我可以通过对文本进行切片和切块来做到这一点，但想知道是否有更优雅的方式

【问题讨论】：

标签： json postgresql arraylist

【解决方案1】：

做一些研究，我认为这样的事情会做到这一点

with data as
(
    select mot_history::jsonb as x 
    from my_table where length(mot_history) > 50

)   
select item_object->'passed',item_object->'expiryDate',position from data,jsonb_array_elements(x) with ordinality arr(item_object, position) 
where item_object->'passed' = 'true'

【讨论】：

如果条件 length(mot_history) > 50 始终满足正确的 JSON 值，这将起作用。