Database size twice as large after mysql dump and re-import
Run the following command so that free space is compressed, and indexes checked and optimized:

mysqlcheck -o -A


After that, try to execute the following query:

SELECT table_schema "Database Name",  
sum( data_length) / 1024 "data size in MB", 
sum( index_length) / 1024 "index size in MB", 
sum( data_free )/ 1024 / 1024 "free space in MB" 
FROM information_schema.TABLES GROUP BY table_schema;


Especially check if the index size in MB column is different between the 2 databases, and show us the results.