Improving the performance characteristics of a database application or system.

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7
votes
1answer
144 views

Lower performance on newest servers

We have several db servers on production, 4 of them with very similar hardware configuration. Dell PowerEdge R620, only difference is that 2 newest ones (bought and configured 3 months ago) have RAID ...
6
votes
3answers
2k views

Dealing with CXPACKET waits - setting cost threshold for parallelism

As a follow-up to my previous question on perf troubleshooting a Sharepoint site, I was wondering if I could do something about the CXPACKET waits. I know the knee-jerk solution is to turn off all ...
5
votes
1answer
2k views

Performance tuning a cascading delete with many foreign keys

I have a delete query that is taking a long time. Looking at the execution plan, I see that most of the estimated cost in the delete query is in a section of the data model that had a lot of data ...
5
votes
2answers
266 views

Cannot tune database any further; what next?

We have a vendor-supplied application. It is under support and we are talking to their developers (we have their largest database size by an order of magnitude), but in the meantime, we have the ...
5
votes
1answer
581 views

How does order of index affect performance in SQL Server?

I am wondering how does order of index affect performance (ASC, DESC) ? If it affects, why ? And which order should I choose ?
4
votes
5answers
1k views

How can I prove that the following T-SQL is bad for performance?

I have recently inherited a codebase with a large amount of Stored Procedures. The system they are supporting is encountering numerous performance problems which I am looking in to. A number of the ...
4
votes
2answers
2k views

Postgresql 9 speeding up indexed inserts (JPA)

I have an application which generates a lot of data which needs to be inserted quickly (something around 13million records). I use JPA 2.0/Hibernate with Postgres 9.1, and I managed to achieve quite a ...
4
votes
1answer
143 views

Table with clustered Index consuming max memory causing low PLE alerts

For one of my server with below configuration i am continuously receiving alerts for low PLE which ranges between 20- 400 and an average of 90-100 in a day: Server: SQL server 2008R2 Databases : ...
4
votes
2answers
81 views

Using Database Engine Tuning Advisor in production

I have a SQL Server 2008R2 OLTP database which is experiencing performance issues during work hours. I would like to run Database Engine Tuning Advisor on this instance but I don't know how it will ...
4
votes
1answer
382 views

SQL Server 2008: Measure tps / select statements per second for a specific table?

There is a discussion how to measure activity against an entire DB: http://stackoverflow.com/questions/5019593/sql-server-2008-transaction-per-second-for-specific-database My question is narrower. ...
4
votes
1answer
816 views

Database under heavier load — all SQL queries start timing out after a period of hours/days

I make a web application which has experienced heavy growth in the past week and it appears my database is seizing up because of it. You can see that everything seemed to be OK until about 3AM this ...
4
votes
1answer
320 views

Tips on improving/refactoring slow query?

Let's play lotto! Ok. I have a numbers table with 80 rows (numbers 1-80): create table dbo.numbers (knum tinyint primary key identity); I have a table with the drawid, and each number drawn. ...
3
votes
2answers
4k views

Configuring PostgreSQL for read performance

Our system write a lots of data (kind of Big Data system). The write performance is good enough for our needs but the read performance is really too slow. The primary key (constraint) structure is ...
3
votes
3answers
330 views

use an Index correctly to optimize queries

I have an SQL database with millions of records and when I'm querying the data like select * from ActCosts where ScenarioID= 456 The tables has 1,323,718 rows and it gives me like 50,000+ rows ...
3
votes
3answers
884 views

Running a DELETE stored procedure but finding degradation in performance in WHILE loop as iterations increase

Have a quick general question. I have a table I'm trying to purge a table. I'm deleting using a WHILE loop with WAITFOR DELAY time of 50ms between batches and 2000 records per batch. The real issue is ...
3
votes
1answer
900 views

Profiling PostgreSQL

We have a system built with Python 2.7, Django, PostgreSQL 9.1 and PostGIS 1.5. In this system there is some extensive validation processes that are, well, intensive. Our machine: SO: CentOS 6 HW: 8 ...
3
votes
1answer
1k views

Understanding sys.dm_exec_query_stats execution_count vs creation_time

I've just downloaded the SQL Server 2012 'Performance Dashboard Reports' and am having some issues interpreting the data shown by one of the results and linking it back to the DMV ...
3
votes
1answer
978 views

How to troubleshoot db/app latency during transaction log backup

I have an application that uses a SQL server (2008 R2) database and we are periodically having performance problems with the application and it coincides with our 15-minute transaction log backups. ...
3
votes
2answers
208 views

Tuning advisor with Extended events?

With SQL traces I was able to analyze them with Database Engine Tuning Advisor to obtain basic recommendations for perf. tuning(missing indexes, statistics,...). Now, with SQL 2012 and Extended ...
3
votes
1answer
65 views

reporting space consumption to files in filegroup - how to reverse-engineer the algorithm spreading data across files

I would like to know how to calculate the distribution of data consumed per file in a filegroup, back to the index (HEAP, CLUSTERED, NONCLUSTERED) storing it. My intention is to define which I/O goes ...
3
votes
1answer
218 views

In-memory SQL Server log file

I have a SQL Server instance that is used solely for the purpose of reporting and also for preparing data to be loaded into Analysis Services. Its data comes from another SQL Server instance which is ...
3
votes
2answers
90 views

What perfmon counters should I use to get the fastest restore possible on an idle system?

I have a development VM running Windows 2012-R2 and Sql Server 2014. I have one disk from a SAN holding the OS and SQL. My backup file is stored locally on the disk. I want to restore database as ...
2
votes
2answers
271 views

What can be done to further enhance performance of Multiple Join and Aggregate Queries?

I have a typical star schema simulated here, and I am mentioning two queries: first query simply joins the fact table with 2 dimension tables and 1 calendar table, and the second query joins and ...
2
votes
1answer
3k views

Why isn't oracle using an index for distinct query ?

This is the scenario SQL> exec dbms_stats.gather_table_stats(user,'TM', cascade=>true) PL/SQL procedure successfully completed. SQL> SELECT SEGMENT_NAME , SEGMENT_TYPE , BYTES / 1024 / ...
2
votes
2answers
7k views

Get username and/or IP address responsible for a query

I use the following query to find performance improvements in queries: SELECT TOP 20 SUBSTRING(qt.text, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN ...
2
votes
1answer
4k views

Optimize PostgreSQL for a lot of INSERTS and bytea updates

What we have (software): PostrgeSQL 9.3 with base configuration (no changes in postgresql.conf) Windows 7 64 bit Hardware: Intel Core i7-3770 3.9 Ghz 32 Gb RAM WDC WD10EZRX-00L4HBAta Drive ...
2
votes
1answer
132 views

Searching a big table for a few results without scanning the whole table

I need to search a very big PostgreSQL table (500+M rows), I want to limit the returned search results, but using the "limit" keyword cant prevent the search over the whole set of data(is it correct?) ...
2
votes
3answers
666 views

Collecting Wait Stats

We currently use a monitoring tool which shows us our top wait stats either by number of waiting tasks or total wait time. Below are the wait stats by number of tasks waiting and also wait time per ...
2
votes
1answer
542 views

MySQL Performance Issues

Over the past 3 weeks we have been having bottle-necking issues at our MySQL server. I have been using MonYOG to watch the processlist in an attempt to get a grasp on the issues. We are aware that ...
2
votes
1answer
468 views

What database and setup can handle several million inserts per minute? [closed]

We have come to a point where for a few of our customers' systems, at peak times, events are generated at that crazy rate. That is, millions of new events per minute (between 1M and 2M). The ...
2
votes
1answer
43 views

Can I throttle individual databases instances on one SQL Server 2005 box

I am running a very old server that has a database that is being permanently retired within 14 months. My company will not invest anymore in hardware or software for this system as we are moving to a ...
2
votes
2answers
111 views

How to auto assign ordinal ranking in mysql with as minimal queries for new rows?

+----+---------+---------+-----------------+ | id | view_id | user_id | ordinal_ranking | +----+---------+---------+-----------------+ | 1 | 10 | 1 | 1 | | 2 | 10 | ...
2
votes
1answer
51 views

Does SQL Server redistribute data after adding an additional data file?

Imagine a database about 30GB in size using 3 data files on the same disk. Someone told me to have one data file per processor implemented to get full performance on all cpus. So if I now add three ...
2
votes
1answer
6k views

Amazon RDS MySQL 5.5 Innodb Lock wait timeout exceeded

Ever since we've moved to Amazon RDS, we've had some pretty crazy performance issues, and today we started having locking issues. Because of that, I figured it was just a timeout issue, and went to ...
2
votes
1answer
89 views

SQL aggregate function performance in a table with many records that is well-indexed

My question is about 3 tables that stores data of a single entity, and there is a report generation feature that refers these tables and calculate COUNT and AVG information. There are three tables: ...
2
votes
2answers
118 views

Need help performance tuning a query

Basically, here is the design of the table (the part that is necessary): id | dt -------- 1 | 2014-05-13 2 | 1900-01-01 3 | 1900-01-01 4 | 2014-05-12 5 | 1900-01-01 So what I am trying to do ...
2
votes
1answer
575 views

SQL Server : How to make “Update Statistics” faster?

We have a table with a 1 column Primary Key on and an UNIQUE Non-Clustered Index with 16 columns. This table has more than 20695780 Rows and on every day new records inserted ...
2
votes
0answers
43 views

How to identify whether a log backup or job executing a SP is causing High Page Reads/sec

For one of my servers( SQL server 2008R2) we can continuously witness High Page Reads/sec during business hours say: from 7 AM to 9 PM EST. I kept the counter settings to monitor the same and found ...
2
votes
1answer
151 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
2
votes
0answers
68 views

Performance of database with transactional data

There are lots of row modifications (several thousands of rows per minute) in our PostgreSQL database that stores transactional data. We have a problem because PostgreSQL runs vacuuming process and ...
2
votes
0answers
171 views

High Cardinality, Time Series Data.. what DB should I use?

I have a system that I'm building based on ElasticSearch. It works great, except I'm having trouble with one of my facets. I've got about 10 million documents, and each document has 1 to 200 ...
2
votes
1answer
169 views

poor and/or unreliable InnoDB performance

I recognize that there are a ton of posts like this, but after reading up on InnoDB performance problems, nothing I tried has helped. I have a database containing four InnoDB tables. The largest ...
2
votes
1answer
508 views

Slow SELECT against clustered index [closed]

I have a table which will hold 10 million rows. I'm seing performance issues when quering it, and wonder if I can somehow improve the schema or query, or if I need to look into sharding. I've used SQL ...
1
vote
3answers
1k views

Do I need to reindex mysql table after bulk delete?

I have a table in MySQL with a lot of INSERT and SELECT at every second. And there is a bulk delete of some older data once in a day. Do I need to reindex the table after delete? I want to increase ...
1
vote
2answers
164 views

Optimizing queries for 25+ million rows

I am using MS SQL, and I have to run several queries on the same table on different criteria. At first I ran each query on the original table although they all share some filtering (i.e Date, status). ...
1
vote
2answers
351 views

Very high load avg for MySQL database [closed]

I have a backend server which response to my clients app, it has more than 20k~25k hit per second and this make my server load average very high, I believe that my MySQL config is not appropriate. In ...
1
vote
2answers
921 views

Should I load the data into Temp table or keep calling it from the normal table? [closed]

I am writing a procedure and find myself using the same select statement with the same where clause a lot. Currently the table holds over 55000 rows and grows about 100 or so rows each day. The two ...
1
vote
1answer
661 views

Optimizing an audit table for inserts and deletes

I'm trying to identify the best way to design a table for audit purposes. Basically I log several last events for many users in one table. There's a limit on the number of records for each user. The ...
1
vote
2answers
7k views

Index for date column for range query in Oracle?

We have a lot: select count(*) from TBL where XDATE between ? and ? and FLD = ?; We expect to boost performance by tuning index on XDATE column (which have DATE type). What type of indexes more ...
1
vote
1answer
281 views

Sort Warnings, finding out the query behind them

I'm troubleshooting a SQL Server 2012 that has started timing out as of a few weeks ago. The server is filled with thousands of sort warnings, at a rate of about 15 warnings per minute. To get the ...