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Editorial Team
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Asked: 2026-05-26T23:01:48+00:00

I have the MYSQL database in the local machine where I’m running the java

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I have the MYSQL database in the local machine where I’m running the java program from.

I plan create a array list of all the entries of a particular table. From this point on wards I will not access the database to get a particular entry in the table, instead I will use the array list created. Is this going to be faster or slower compared to accessing the database to grab a particular entry in the table?

Please note that the table I’m interested has about 2 million entries.

Thank you.

More info : I need only two fields. 1 of type Long and 1 of type String. The index of the table is Long , not int.

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  1. Editorial Team

    No, it’s going to be much slower, because to find an element in an ArrayList, you’ve to scan sequentially the ArrayList until your element is found.

    It can be faster, for a few hundreds entry, because you don’t have the connection overhead, but with two millions entry, MySQL is going to win, provided that you create the correct indexes. Only retrieve the rows that you actually need each time.

    Why are you thinking to do this? Are you experiencing slow queries?

    To find out, in your my.cnf activate the slow query log, by uncommenting (or adding) the following lines.

    # Here you can see queries with especially long duration
log_slow_queries    = /var/log/mysql/mysql-slow.log
long_query_time = 1

    Then see which queries take a long time, and run them with EXPLAIN in front, consider to add index where the explain command tells you that is not using indexes, or just post a new question with your CREATE TABLE statement and your example query to optimize.

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