Contents
Why does SQL Server slow select from large table?
Table is receiving about 100k+ records each day. I have indexes on each column except MetaId, as it is not used in ‘where’ clauses The problem is when i want to pick up eg. latest 100 records for desired SourceUserId Query sometimes takes up to 4 minutes to execute, which is not acceptable. Eg.
Why does SQL query take so much time?
The query takes up 1.90 seconds. If I run the query again it takes 1.66 seconds. Why does it take more time in the first run? In order to speed it up I created indexes on the two columns used in the query. SQL> create index ind_tab3_orgid on tab3 (COL1); Index created.
Why is mysql query so slow in 5.7?
In MySQL 5.7 it is taking over 11.5 seconds at first and 1.4 seconds every recurring execution without restarting MySQL. And the more LEFT JOINs I add to the query, the slower the query becomes in MySQL 5.7. Both instances now run on the same machine, on the same hard drive and with the same my.ini settings. So it isn’t hardware.
Why does SQL-query execute slower after indexes are created?
This time the query came back in 2.9 seconds (sometimes it took 3.9 seconds too). My goal is to minimize the query execution time as much as possible. But after adding indexes or after computing statistics the query time just kept increasing. Why is this happening and how can I improve even by keeping the indexes?
How to improve SQL Server query performance on large tables?
I have a relatively large table (currently 2 million records) and would like to know if it’s possible to improve performance for ad-hoc queries. The word ad-hoc being key here. Adding indexs is not an option (there are already indexs on the columns which are queried most commonly).
How long does it take to execute a SQL query?
Takes several minutes. See execution plan below: Additional detail from the table scan: SQL Server Execution Times: CPU time = 3945 ms, elapsed time = 148524 ms. The server is pretty powerful (from memory 48GB ram, 24 core processor) running sql server 2008 r2 x64.
What are the execution times of SQL Server?
SQL Server Execution Times: CPU time = 3945 ms, elapsed time = 148524 ms. The server is pretty powerful (from memory 48GB ram, 24 core processor) running sql server 2008 r2 x64. I found this code to create a table with 1,000,000 records.
Is it possible to index a large table?
Although indexes are supposed to make queries faster, they cannot absolve you from the sins you committed while writing the queries. Also, creating indexes comes with a cost, which is something if not thought about, can kill database performance in all aspects and not just reading data. Slow query issues a r e seen more often with large tables.
How to speed up indexing in SQL Server?
If you have a clustered index that is not on an identity numeric field, rearranging the pages can slow you down. If this is the case for you see if you can improve speed by making this a non-clustered index (faster than no index but tends to be a bit slower than the clustered index, so your selects may slow down but inserts improve)
How to optimize queries for 25 + million rows?
I am only interested in 4 columns for my criteria and the result should output the count only, for all queries. columns needed: TABLE, FIELD, AFTER, DATE, and there is an index on each of DATE and TABLE. After creating a temp table with only the fields I need, it went down to a 1:40 minutes, which is still very bad.
Why are simple Selects on InnoDB 100X slower than MyISAM?
First MyISAM was slow, but oke. Then InnoDB made things bad, similar to the 100x slower in this question and after changing the setting InnoDB got 10x faster then MyISAM. My default setting was on 8MB which is far to little. Based on your both the query and table it seems like you are selectikg data from a time-series table.
How to test the performance of a query?
Test the query with an table hint forcing the use of the index, if that condition is reasonably selective. If the optimizer is currently choosing the index seek, test performance with an INDEX (0) or FORCESCAN hint to scan the heap. Beyond that, you could look to improve the scan of the heap a little by removing some of the unused space (370MB).