Why is this query sometimes fast and sometimes slow?

Why is this query sometimes fast and sometimes slow?

SQL Server does an index seek on our IX_Reputation index to find the 5,305 rows that match, then does a key lookup to get the SELECT * part (because the index doesn’t cover all those fields.) Look at the execution plan, hover your mouse over the index seek, and you’ll see that SQL Server expected 5,305 rows – and 5,305 actually came back. Awesome.

Can a 10 second query cause performance degradation?

The slow queries definition might differ in different cases since there are certain occasions that even a 10 second query is acceptable and still not slow. However, if your application is an OLTP, it’s very common that a 10 second or even a 5 second query is an issue or causes performance degradation to your database.

How to fix a query in SQL Server?

The easiest way to figure that command out is to run sp_BlitzWho *! There’s a column called “fix parameter sniffing” that has a command to remove a single plan from the cache. This has the same drawbacks as recompile, though. Processes currently running it.

Where to put slow query logs in MySQL?

You must ensure that the variable slow_query_log is set to ON, while the slow_query_log_file determines the path where you need to place your slow query logs. If this variable is not set, it will use the DATA_DIR of your MySQL data directory.

Why is SQL Server so slow on SSMS?

Slow in the Application, Fast in SSMS? Understanding Performance Mysteriesis another excellent reference. I’ve concluded (perhaps incorrectly) from these little experiments that the reason for the slow-down is due to how SQL’s cached execution plan is set up — when the query is a little different, it has to create a new execution plan.

What happens when a query hits SQL Server?

And it’s usually your friend. When a query hits your server, a plan has to be compiled. To save time and resources later, an execution plan is cached based on the estimated rows that parameter will cause your code to process and return.

How long does it take a SELECT query to run?

This question is I have a SELECT query that runs fine if submitted the 1st time (takes about 3 seconds), but if I submit it right after again, it could take anywhere from 22 to 37 seconds (on a pretty consistent basis).

Why is SQL Server unable to run as fast as SQL sever?

But what can account for SQL Server being unable to run as fast as SQL Sever running a query, if not parameter sniffing. My next attempt will be to have StoredProcedureA call StoredProcedureB call StoredProcedureC call StoredProcedureD to query the view.

Why does SQL Server run slow with different execution plan?

But putting the same SQL in a stored procedure runs slow, and with a totally different execution plan And it still runs the same (badly), and I’ve also changed the stored procedure to And back again, trying to really trick it into recompiling.

What to do when SQL Server is slow?

The next tool is the “Query Store”. This is helpful and could save your life in situation where you were called in the middle of the night to check why SQL Server was slow 1 hour earlier. Generally, prior to SQL Server 2016, without any third-party application or custom solutions, you are not able to look at the history of query execution.

How to see top resource consuming queries in SQL Server?

Right Click on Top Resource Consuming Queries and select “View Top Resource Consuming Queries”, you will be taken to the window showing these high resource consuming queries. You can customize the view by selecting an appropriate “metric” like Duration, CPU Time, Logical Read or Memory Consumption.

Why does the execution plan differ from the EXPLAIN PLAN?

This can differ from the plan during actual execution for a SQL statement, because of differences in the execution environment and explain plan environment. Execution plans can differ due to the following: The execution and explain plan happen on different databases.

Which is the core of oracle’s execution plan?

A statement’s execution plan is the sequence of operations Oracle performs to run the statement. The row source tree is the core of the execution plan. It shows the following information: In addition to the row source tree, the plan table contains information about the following:

Can a execution plan differentiate between well tuned statements?

The execution plan operation alone cannot differentiate between well-tuned statements and those that perform poorly. For example, an EXPLAINPLANoutput that shows that a statement uses an index does not necessarily mean that the statement runs efficiently. Sometimes indexes can be extremely inefficient.

What should I do if my SQL Server is running slow?

If the bad execution plan is still cached you can analyze it, and you can also check the execution stats. The execution stats will contain information as logical reads, CPU time and execution time. These can give strong indications what the problem is (eg. large scan vs. blocking).

Can a query produce 2 different plans with the same parameters?

The same query can produce 2 different plans with 2 different parameters. (More complex queries can even produce more different plans than that.) Let’s put it in a stored procedure and see what happens.

Why does my SQL query take so long?

You’ll query a view, which queries another view, which queries a table. This adds extra complexity and can slow down your query. Consider only accessing one view for your query. If you have multiple views for a query, where a view is querying another view, consider creating a new specialised view for it.

What’s the best way to speed up a SQL query?

SELECT * is a way to show all columns in a table. It’s faster than typing out all of the columns. It can be tempting to select all of the columns and just let your application or report use what it needs. However, selecting more columns than what you need can slow down your query, as the database needs to do extra work to retrieve the columns.

How can I fix a slow SQL query?

Here’s the fix: Test your query by inserting a LIMIT statement like this: SELECT phone_type, state, buyer_name, purchase_time FROM global_smartphone_sales WHERE YEAR (purchase_time) = ‘2015’ If the query involves more than 2000, the “LIMIT 2000” will only bring back the first 2000 records.

How to fix SQL Server query taking too long?

Either you can kill that session or commit the transaction in it. For me disconnecting the SQl database and reconnecting it back helped to solve the problem. The problem was while updating a table (few transactions have been triggered/ they need commit).

Why does SQL take 15 minutes to execute?

2) In rare cases it can be due to network traffic, also where we will not have consistency in the query execution time for the same input data. I too faced a problem where we had to create some temp tables and then manipulating them had to calculate some values based on rules and finally insert the calculated values in a third table.

What can I do to make MySQL Query faster?

To make the query faster in your case there have three things you can do. Don’t know it will help you or not but According to SQL optimizing query concepts, it must help. Create CLUSTERED INDEX for all your tables. Cluster index makes the SELECT query faster at 30:70 of ratio.