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Why are composite indexes so slow in MySQL?
This also means that by the time it does the created_at match, it will only have the rows with status ‘error’, so the dataset it needs to go through is considerably smaller than in the original query. Duration query is not doing so good, we can see MySQL picked the created_at index which we added, but the query itself still takes around 1.6s.
How to delete table based on composite key?
I have two identical tables (column wise, not data), table1 and table2. I wish to delete the records in table1 in which the composite key (col1, col2) exists in both tables.
Why is delete in Big Table so slow?
delete can be slow if big table has recursive foreign key. if so, find opportune time, disable dependend services, disable recursive foreign key, perform massive delete, then restore foreign key again.
Why is SQL Server Delete statement in SQL so slow?
After inspecting an SSIS Package (due to a SQL Server executing commands really slow), that was set up in a client of ours about 5-4 years before the time of me writing this, I found out that there were the below tasks: 1) insert data from an XML file into a table called [Importbarcdes].
Why is the duration query in MySQL slow?
Duration query is not doing so good, we can see MySQL picked the created_at index which we added, but the query itself still takes around 1.6s. So we are stuck again, we added indexes for all the columns used in the WHERE clause but the query is still slow, now what?
Is it possible to speed up MySQL status query?
So status query sped up considerably, about 10 times, but duration query remained slow. One thing to take away from this is that the fact you have all your columns used in WHERE clauses indexes, doesn’t mean the queries magically all become fast.
Is it bad to have index list in MySQL?
So creating a bunch of indexes you are actually not using will be bad for the performance of your database. It is also a good practice to visit your index list from time to time in the application development flow. So you can remove the indexes you are not using or add ones that’ll speed up your queries.
Is it faster to search by Index in MySQL?
If there weren’t any indexes, you’d have to go through the whole book searching for pages that contain the subject. As you can imagine, it’s way faster to search by an index than having to go through each page. Therefore, adding indexes to your database is in general speeding up your select queries.
Why is mysql query so slow within date range?
Wrapping the column in a function (like DATE (), as in your query) disables the MySQL optimizer from using a range scan operation. With your query, even with an index available, MySQL is doing a full scan of every single row in the table, each time you run that query.