使用 PostgreSQL 9.4 计算 JSONB 数组长度
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Calculate JSONB Array Length Using PostgreSQL 9.4
提问by Joshua Burns
I'm running the latest version of PostgreSQL 9.4.5-1.pgdg14.04+1, and am attempting to calculate the length of a JSONB array using the JSON_ARRAY_LENGTHfunction as described in the PostgreSQL 9.4 Documentation
我正在运行最新版本的 PostgreSQL 9.4.5-1.pgdg14.04+1，并尝试使用PostgreSQL 9.4 文档中JSON_ARRAY_LENGTH描述的函数计算 JSONB 数组的长度
Here is the exact query I'm attempting to run:
这是我试图运行的确切查询：
SELECT JSON_ARRAY_LENGTH('["hi","ho"]'::jsonb) AS length
When I run that query, I would expect to be returned a value of 2, but instead am encountering the error: ERROR: function json_array_length(jsonb) does not exist
当我运行该查询时，我希望返回的值为2，但我遇到了错误：ERROR: function json_array_length(jsonb) does not exist
Am I missing something very obvious in the documentation? It specifically states you may call JSON_ARRAY_LENGTHpassing either a jsonor jsonbdata-type. I'm explicitly casting to jsonbso I'm at a bit of a loss.
我是否遗漏了文档中非常明显的内容？它特别说明您可以调用JSON_ARRAY_LENGTH传递 ajson或jsonb数据类型。我明确地投射到jsonb所以我有点不知所措。
Has anyone else encountered this problem, or would someone point out what I'm doing wrong here?
有没有其他人遇到过这个问题，或者有人会指出我在这里做错了什么？
UPDATE: I Mis-Read The Documentation
更新：我误读了文档
I should have been calling JSONB_ARRAY_LENGTH, not JSON_ARRAY_LENGTH. Notice the "B" after "JSON". Thanks guys.
我应该打电话JSONB_ARRAY_LENGTH，不是JSON_ARRAY_LENGTH。注意“JSON”后面的“B”。多谢你们。
回答by Jorge André Pereira
SELECT jsonb_array_length('["question","solved"]') AS length;
or
或者
SELECT json_array_length('["question","solved"]') AS length;
