- Instances of
BLOB
orTEXT
columns in the result of a query that is processed using a temporary table causes the server to use a table on disk rather than in memory because theMEMORY
storage engine does not support those data types (see Section 8.4.4, “How MySQL Uses Internal Temporary Tables”). Use of disk incurs a performance penalty, so includeBLOB
orTEXT
columns in the query result only if they are really needed. For example, avoid usingSELECT *
, which selects all columns.
【参考资料】
1、http://dev.mysql.com/doc/refman/5.6/en/blob.html
时间: 2024-08-24 15:56:37