为什么以下MySQL语句会导致特定表（T_DCE）上的元数据锁定？
SELECT M_COUNTRY.ICAO,
M_DOCUMENTTYPE.DocumentType,
T_DCE_CHECKS.CheckResult_ID
FROM T_DC
INNER JOIN M_COUNTRY
ON T_DC.ONationality_ID=M_COUNTRY.ID
INNER JOIN M_DOCUMENTTYPE
ON T_DC.ODocumentType_ID=M_DOCUMENTTYPE.ID
INNER JOIN T_DCE
ON T_DC.ID=T_DCE.T_DC_ID
AND T_DC.Date=T_DCE.Date
INNER JOIN T_DCE_CHECKS
ON T_DCE.ID=T_DCE_CHECKS.T_DCE_ID
AND T_DCE.Date= T_DCE_CHECKS.Date
WHERE (T_DC.Date BETWEEN '2017-01-01' AND '2018-12-31')
AND M_COUNTRY.ICAO IN ( 'ALB', 'ARE')
AND T_DCE_CHECKS.CheckResult_ID='57'
GROUP BY M_COUNTRY.ICAO, M_DOCUMENTTYPE.DocumentType
ORDER BY M_COUNTRY.ICAO, M_DOCUMENTTYPE.DocumentType
;
要获取有关导致元数据锁定的语句的信息，我使用了this blog post on percona中提到的过程。
Process(es) that have the metadata lock:
PID 5612772 has metadata lock on MySchema.T_DCE with current state [Sending data] for 81055 seconds and is currently running
[SELECT M_COUNTRY.ICAO, M_DOCUMENT...
我不确定我是否正确阅读了文档，但是仅当我明确使用LOCK TABLE或DDL / DML语句时，才不会发生表锁定吗？
系统环境：