Using a test script, the average time to complete an insert is a few ms. But about 3% of the time, the insert takes between 0.5 and 3 seconds to complete. If I run the same query 1000 times about 970 finish in under 10ms, while 30 take over 500ms.
I'm running a fairly recent build of Raspbian from a few months ago and SQLite 3.8.4.
The process doing the inserts jumps from about 5% CPU usage to 10% when the slow inserts happen, but otherwise the CPU usage is normal.
How can I find out what's going on here, how would I know if SQLite is waiting on the OS to write, or if it's waiting to acquire a lock, or something else?
Edit: Here is the table schema
create table n (id INTEGER PRIMARY KEY,f TEXT,l TEXT);
And Here is the query I'm running
insert into n (f,l) values ('john','smith');
Related
Does snowflake incur charges when I abort long running queries?
Yes. Because you pay for every second the warehouse is/was running (after the first 60 seconds which you get billed for just for starting the warehouse).
You also get billed if the long running query hits the execution timeout limit (default is something like 4 hours) you pay for those minutes, and you still have no answer.
But if you had the warehouse running many queries, and you run yet another query and then after time abort the new query, the warehouse was running so the new query itself will not be charged. But at the same time, the other queries run fractionally slow.
CPU is charged by the Virtual Warehouse being up and running, not by individual query. If you abort a query, and suspend the VWH you’re only charged during the time the VWH was in a running state.
im trying TPC-H benchmark on my Oracle database, testing takes place on a 10GB dataset. Currently I have target_memory set to 7GB, but the current test time is 18 minutes. The biggest problem is with the lineitem table(7,5GB), because its size does not fit in the cache and with each new query, all data must be reloaded from disk. Do you have any ideas how to speed up the test?
I've already tried the parallelization offered by the optimizer, but it ran even slower with that test due to the HDD and index doesnt work here, because for example in Q1 Oracle need to proccess almost 97% of table lineitem, which is the largest table with a size of 7.5 GB.
Sqlite query gets really slow after inserting 14,300,160 rows (the db size is about 3G).
Supposed I have a table called test and I have created an index on column TIMESTAMP prior to insertion. A simple
SELECT DISTINCT TIMESTAMP FROM test;
Would run about 40 seconds, but after I do:
ANALYZE; -- Takes 1 minute or so on this DB
The same query runs 40 milliseconds, which is expected since the column is indexed.
As I'm using the database for soft real time applications, it is not possible to lock the DB for 1 minute or so just to run ANALYZE from time to time. I suspect that the insertion is breaking the index, hence the ANALYZE helped. Is that really the case? And if so, is there anyway to prevent this from happening?
Up until recently, I've been creating indexes (<20s) and running heavy queries (<10s) relatively quickly on a database containing tables that have up to about 10-12 million rows each.
My newest database has tables with up to 40 million rows each and both my index creation and querying is suffering tremendously.
Index creation is timing out (even with my Tools > Options > Designers > Table and Database Designers > Transaction Timeout being upped to 120 seconds)
Queries that had been taking me 10 seconds are now taking 40-50 seconds in SQL Server Management Studio (which is logical), HOWEVER:
Those same queries which had been taking 5-10 seconds each using library(RODBC) and sqlQuery() through R are now taking around 4-5 minutes each.
I'm working on an i7, recently upgraded to SQL Server Management Studio Enterprise (but the issue was occurring prior to upgrade), and I need these queries running at least semi-optimally.
Each query pulls about 200,000 values, but needs to traverse the entire table; thus, a non-clustered index appeared to make sense, but index creation is timing out.
What have I already done?:
Upped the Transaction Timeout from 30 seconds to 120 seconds.
Increased the Index Creation Memory (Server Properties > Memory) from 0 to 33000.
Increased Minimum Memory per Query from 1024 to 3500.
Created a miniature version of a populated table (re: 4 million rows):
Query time is optimal. (retrieving 40,000 rows (10%), ~2sec)
Index creation is optimal. (<10s)
I'm not sure where the bottleneck is occurring, any ideas?
I have a client app that is submitting the following command to SQL Server 2005. At a specific time of day we are having performance issues where some of the requests are taking between 2 - 8 seconds to run when the norm is below 300ms. We are researching SQL Server options as well as all external variables that can impact the server.
My question here is how/why can a request take 8 seconds and during this time many other identical requests start and finish during this 8 second window? What can be preventing the 8 second call from finishing, but not prevent or slow down the other calls?
Running server profiler during this time the number of reads are around 20 and the writes less than 5 for all (long and short durations) the calls.
The table being inserted into has around 22M records. We are keeping about 30 days worth of data. We will probably change the approach to archive this data daily and keep the daily insert table small and index free, but really want to understand what is happening here.
There are no triggers on this table.
There are 3 indexes for GUID, Time and WebServerName (none are clustered)
Here's the command being submitted:
exec sp_executesql N'Insert Into WebSvcLog_Duration (guid,time,webservername,systemidentity,useridentity,metricname,details,duration,eventtype)values(#guid,#time,#webservername,#systemidentity,#useridentity,#metricname,#details,#duration,#eventtype)',N'#guid nvarchar(36),#time datetime,#webservername nvarchar(10),#systemidentity nvarchar(10),#useridentity nvarchar(8),#metricname nvarchar(5),#details nvarchar(101),#duration float,#eventtype int',#guid=N'...',#time='...',#webservername=N'...',#systemidentity=N'...',#useridentity=N'...',#metricname=N'...',#details=N'...',#duration=0.0,#eventtype=1
The probable reason why is heap fragmentation; you didn't mention if you had some sort of index maintenance going on, so I'm assuming that it's non-existent. The best way to minimize fragmentation is to build a clustered index on a monotonic value (a column with a naturally increasing order). I'm not sure what the time column is supposed to represent, but if it's the time of insertion, then it might be a good candidate for a clustered index; if not, then I'd add a column that captures the time inserted into the table and build a clustered index on that.