现象
今日在使用mysqldump导出MySQL5.7版本的数据时，报错：
mysqldump版本：8.0.17
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mysqldump -h172.16.0.100 -P3306 -B testdb --compact > testdb_20191123.sql
**Warning: A partial dump from a server that has GTIDs will by default include the GTIDs of all transactions, even those that changed suppressed parts of the database. If you don't want to restore GTIDs, pass --set-gtid-purged=OFF. To make a complete dump, pass --all-databases --triggers --routines --events. **
**mysqldump: Couldn't execute 'SELECT COLUMN_NAME, JSON_EXTRACT(HISTOGRAM, '$."number-of-buckets-specified"') FROM information_schema.COLUMN_STATISTICS WHERE SCHEMA_NAME = 'testdb' AND TABLE_NAME = 'st_acc';': Unknown table 'column_statistics' in information_schema (1109)**
备份失败，按照提示，是因为找不到information_schema.column_statistics这个元信息表。
解决
按照8.0版本的文档提示，mysqldump加入了该参数 –column-statistics，该参数默认为打开，在dump时，会在information_schema.column_statistics表中检查导出表的信息。
https://dev.mysql.com/doc/refman/8.0/en/mysqldump.html#option_mysqldump_column-statistics
所以若需要dump出MySQL5.7的数据，需要设置其为false
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mysqldump -h172.16.0.100 -P3306 -B testdb --compact --column-statistics=0 > testdb_20191123.sql