MySQL 中的最大 JSON 列长度
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/40711101/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Max JSON column length in MySQL
提问by mark
What's the max number of characters I can store in a JSON column in MySQL? I don't see this mentioned in the MySQL manual.
我可以在 MySQL 的 JSON 列中存储的最大字符数是多少？我在 MySQL 手册中没有看到这一点。
回答by Bill Karwin
Here's a demo of what @JorgeLondo?o is talking about.
这是@JorgeLondo?o 所谈论内容的演示。
Set the server's max allowed packet size:
设置服务器的最大允许数据包大小：
mysql> set global max_allowed_packet=1024*1024*1024;
Exit and open the mysql client again, this time setting the client max packet size to match:
退出并再次打开 mysql 客户端，这次设置客户端最大数据包大小匹配：
$ mysql --max-allowed-packet=$((1024*1024*1024*))
Create a test table with a JSON column and fill it with the longest JSON document you can:
创建一个带有 JSON 列的测试表，并用最长的 JSON 文档填充它：
mysql> create table test.jtest ( j json );
mysql> insert into test.jtest
set j = concat('[', repeat('"word",', 100000000), '"word"]');
Query OK, 1 row affected (1 min 49.67 sec)
mysql> select length(j) from test.jtest;
+-----------+
| length(j) |
+-----------+
| 800000008 |
+-----------+
This shows that I was able to create a single JSON document with 100 million elements, and MySQL stores this in approximately 800MB.
这表明我能够创建一个包含 1 亿个元素的 JSON 文档，MySQL 将其存储在大约 800MB 中。
I didn't try a longer document. I assume it maxes out at 1 GB, which is the largest value you can set for max_allowed_packet.
我没有尝试更长的文档。我假设它最大为 1 GB，这是您可以为 max_allowed_packet 设置的最大值。
回答by Jorge Londo?o
The size of JSON documents stored in JSON columns is limited to the value of the max_allowed_packetsystem variable. (While the server manipulates a JSON value internally in memory, it can be larger; the limit applies when the server stores it.)
存储在 JSON 列中的 JSON 文档的大小受限于max_allowed_packet系统变量的值。（虽然服务器在内存中内部操作 JSON 值，但它可以更大；当服务器存储它时，限制适用。）
Command-Line Format --max_allowed_packet=#
System Variable Name max_allowed_packet
Variable Scope Global, Session
Dynamic Variable Yes
Permitted Values Type integer
Default 4194304
Min Value 1024
Max Value 1073741824
