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Why does oracle query run faster the second time?
Another factor that makes the initial query slower is the fact that Oracle has to hard parse a query the first time it sees it – this involves finding the optimum (as far as the Oracle optimiser is concerned) execution plan for the query & is quite computationally (CPU) expensive, thus takes time.
How many seconds does it take to run a query?
The first time I run the query, it’s 2 seconds. Subsequent times it’s 3, 4, or even 5 seconds. This happens consistently – if I change the spacing, I get 2 seconds again, then it goes back up.
How long does it take to execute a query in MySQL?
If you have a very large table in MySQL with an index, and you execute this for the first time, it may take 2 minutes. While if you execute it again it will return right away. You can use the Help-> [SQL Log] to help diagnose the query execution speeds.
How to see if Oracle fetched data from disk?
In order to see whether Oracle fetched the data from disk, or used its cache you can enable autotrace in SQL Developer. Physical reads are pulled from disk.
How long does it take an oracle query to run?
However, it does not have any ability to tell you how long a corrective action might take. If you have a large table with millions of rows, it may take days depending on the size of the rows. Was this post helpful?
How long does it take to build a temporary index in Oracle?
On a large table this could take a long time either way, maybe even longer than the 4 or 5 minutes you’re seeing. Once the data is retrieved, the temporary index would be dropped in the background. When you do another query, Oracle needs to build a new temporary index, which is why it takes that long for every query.
Why does Oracle have to read every row?
You don’t have an index on either of these columns so Oracle has to read every row. But if you do a query on KEY=12345 or KEY BETWEEN 12345 and 23456, it’s easy to find the exact match or the range.
Why is SQL query slow the first time?
Whereas for a similar SQL Server database (with that same table in schema and size), it takes just 1 second the first time, the next times it reports 00:00:00 My customers want it faster but really it’s limited by their database/server.
Is it slow to select from that table?
It is much slower than select * from that_table, really strange. UPDATE with tracing info : By using tkprof and some statement to enable tracing for the current session, I could obtain the trace-file, analyzed it into an output text file (using tkprof ).