php - Fatal error: Allowed memory size of 50331648 bytes What does this mean?

Question

Fatal error: Allowed memory size of 50331648 bytes exhausted (tried to allocate 78 bytes) in /home/u500028/ews/workspace/php/appcode/webroot/htdocs/ThinkPHP/Library/Think/Db/Driver.class. php on line 289

What does this sentence mean

Answer 1

The memory has overflowed. Querying a large amount of data should be done in batches