An evaluation of whether a system works well enough to be fit for purpose. Normally performance refers to the speed with which a system completes an operation or set of operations over time.

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128 views

postgresql 8.3 possible checkpoint and memory misconfiguration

I am using postgresql 8.3 in a read/write heavy application where data are being written to the database from a background process while they are also being read/written from a web application. At ...
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199 views

How to make Greenplum 4.2.3 only scan the intended partition?

When I uses unnest() in a View, and uses that View in a select statement, Greenplum seems to fail in only searching for the intended partition and search through all the partition of the main table ...
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145 views

Most efficient way to sort data fields into SQL

I'm trying to decide on the most efficient way to sort various data values. Here's how the data arrives: Device X sends a text string "name=value&name2=value&name=value" On arrival that ...
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2k views

'Incorrect datetime value: for column 'last_login' at row 1'

i am getting below error: Last_SQL_Errno: 1292 Last_SQL_Error: Error 'Incorrect datetime value: '2013-03-10 02:00:00' for column 'last_login' at row 1' on query. Default database: 'platform'. ...
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480 views

Efficiently retrieve big amount of data based on date range

Table EVENTS TimeStamp |O.Name |Location |Source | 2008-11-12 |Pretorian|Európe |England | 2009-12-24 |Lex Rosa |Európe |Italy | 2010-01-01 |Nasdaq |USA |Whasington | ...
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404 views

How to calculate running total based on dynamic values?

I need to calculate the running total in which the target column is changing along with the time. Its something which aws does. Charging based for only what you use. So how do I aggregate sum of ...
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126 views

Why is this table structure so slow to CRUD?

I have a table that I am using for queuing emails. Unfortunately, adding to or reading from this table becomes horrendously slow after adding about 50 records. -- Table "mail_queue" DDL CREATE TABLE ...
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826 views

Oracle 10g - Sudden change in execution time for specific query

After the DBAs fiddled with some parameters in our Oracle 10g Production Environment, most queries became a little faster. But a single query (a quite complex one) became dramaticaly slower - it went ...
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371 views

Finding the bottleneck by analyzing Munin graphs

We’ve been experiencing some issues with our database server during peak hours. In our Nginx error-log we can see that a lot of requests get timed out. The requests are also very slow. We have had ...
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169 views

Multi-Table Join to Single Destination

I am having a serious performance issue with join together four tables and placing the results (in a certain permutation) into one destination table. I am using MSSQL 2008 and good ole T-SQL. To ...
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32 views

Data warehousing: data transfer process too slow with larger batches

I have two primary instances of SQL Server, one for OLTP and one for reporting. The data warehouse for reporting is basically a Type 2 SCD: every table has DWDateStart and DWDateEnd columns and the ...
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21 views

What minimum RAM should the server have for a Django application with Postgresql server?

I have a Django application. The database is Postgresql with 8GB size. We are also using Nginx with gunicorn. Will a 4GB server be enough for good performance ( like on Digital Ocean) ? I was under ...
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10 views

JDBC4/SQL or Hibernate/ORM?

I have an upcoming thesis project that may be used by the school itself if the system proves to be good. It is a web application (Struts2) for an Online Teacher's Performance Evaluation System. The ...
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5 views

Can MySQL Index Merge an Composite index with a single column index?

I am tuning a query and currently have an index as following : Index 1 : (col1, col2) An example query would be : SELECT * FROM t1 WHERE col1 = '1' AND col3 = '2'; I have created an index on ...
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38 views

Physical Table being used a Temp Table in a warehosue. Any advantage?

As I stated in previous posts I've inherited a warehouse based on SQL Server framework. In my continuous review of existing components and the practices adopted by the predecessors I found something ...
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21 views

Database design for price comparison site - too complex?

I'm working on a regular price comparison site with two exceptions. I want to show price history and also allow users to subscribe to a product with a specific size and color. As a result, I've ended ...
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31 views

MySQL: Optimize query with a range and distinct count

I have a query on a large table with millions of rows that looks like this: SELECT COUNT( DISTINCT clicks.tx_id ) AS unique_clicks_count , clicks.offer_id FROM clicks WHERE ...
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36 views

Horribly slow MySQL (InnoDB) updates, multiple workers

I've created a PHP daemon that reads records from a MySQL InnoDB-table, analyses it and then updates the record. This process is spread between multiple workers (and servers) using Redis. However, ...
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9 views

How to find an application for a specific system?

I have a distributed storage platform that I wanted to test. I launched a benchmark (i.e. IOzone) over it, given the following workload: I/O size = 4kB, 100% read, and 100% write, random access. ...
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17 views

Galera cluster consume many CPU percent and CPU high load

I have implemented a cluster include three nodes: two stored nodes and one garbd (also haproxy - load balancer). Some information about servers: SSD 480G Raid1 Memory 32G Swap 16G 2xCPU, number of ...
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36 views

PostgreSQL queries slower than before?

I am using PostgreSQL 9.3 server on my production server. Everything had been working fine for the past couple of months. But since the past week or so, PostgreSQL seems to have becomes very slow with ...
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35 views

Looking for a recipe to merge multiple rows to single row

I have a aggregation table that is written by multiple processors (around 20). Each row has a composite key - location-id, campaign-id,... and aggregate stats about it. I need to merge the ...
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57 views

Very poor MySQL query performance after upgrading from server-5.5 to server-5.6

I'm in the process of trying to migrate a database from an old server to a new one. The old server is running an Xampp installation which has been more than adequate for the use case. For the new ...
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34 views

Billion records mysql performance with large result sets

I'm currently developing an application which will have several mysql tables where 3 of them have very large amounts of records. The thing is that my app will have to sync each account on a hourly ...
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41 views

MySQL Crash due to “InnoDB Assertion” after Query

Current setup: Ubuntu 12.04 LTS MySQL 5.5.31 Current Use: Slave - Only ETL queries 64 GB RAM Intel(R) Xeon(R) CPU X5670 @ 2.93GHz - 12 Cores - Hyperthreaded (24 Logical) MySQL Main Settings: ...
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27 views

MySQL performance_schema not working properly?

I have MySQL 5.6.19 community server running on my Ubuntu 14.04. Lately I have been trying to monitor MySQL server using performance_schema. Previously I used to do this by running SHOW FULL ...
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13 views

MySQL Cluster Disk Data Tables - worth it?

I'm working on improving the performance of our 4-node MySQL cluster for a webapp with lots of DB writes. We've got a Solr index sitting 'on top' of the SQL in order to give us fast querying, and we ...
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38 views

MYSQL : Copying to TMP table nightmare

I'm having a (AFAIK) random issue. My server is MySQL and I have a query that is sometimes 10000 times slower as you can see on this screensot : http://snag.gy/vJJ39.jpg The long time occurs during 2 ...
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29 views

is there any limit of MySQL status variable value?

As we know MySQL status variable is a counter variable since the service start. MySQL service in my DB server restart every week (on sunday). Below is my observation since last few week: Suddenly ...
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67 views

MySQL: What should I do if too many tables opened during peak hours?

In Peak hours: When I run below statement, I found around 100 tables out of 250 have opened. show open tables where in_use>0; There are around 10 tables for which in_use value are >50. Storage ...
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22 views

What is the recommended pgpool mode?

I'm trying to determine which pgpool mode to use (http://www.pgpool.net/docs/latest/pgpool-en.html#config). In order of importance my requirements are: All nodes accessible via shared public ...
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31 views

Optimal config for a small vserver with ispconfig

I have a vserver with debian wheezy, 1GHz CPU single core, 512MB RAM and only 8GB HDD. Owncloud is running, but has its own database-engine How should I configure Mysql so it doesn't slow down the ...
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79 views

Will I still benefit from provisioned IOPS in RDS on a smaller non-PIOPS-Optimized instance type?

Quote from the docs: If you are using Provisioned IOPS storage, we recommend that you use the db.m3.xlarge, db.m3.2xlarge, db.m1.large, db.m1.xlarge, db.m2.2xlarge, db.m2.4xlarge, ...
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80 views

Very slow response even with a high number of available connections

I'm running this server for data mining purposes. It runs several compute-intensive data mining applications in parallel and does simultaneous access to the MySQL server. Here are the ...
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175 views

General error: 1615 Prepared statement needs to be re-prepared

I have been running into this issue every time I try and sync a medium size JSON object to my database so we can perform some reporting on it. From looking into what can cause it I have come across ...
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18 views

Joining 2 big tables turn into a server down problem

Recently I was using a database (MySQL with Workbench) in the company that I work for (I'm a business analyst, not a DBA), and wrongly I created a query joining 2 tables that basically are the same. ...
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64 views

Why would call to scalar function inside a Table Value Function be slower than outside the TVF?

I am writing a Table Value Function, calling the function takes 10x as long as directly running the code. I traced this to a call to a multi-line scalar function inside the TVF. The call to the ...
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22 views

How to figure out how to split a table using the proper scheme

If you have a big table that you want to partition and you have 2 candidates as the partitioning key (in the sense that 50% of the queries use one column and 50% of the queries use the other column ...
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53 views

is this dead simple query too slow?

I have added and removed a few indexes from my user table and, while testing, didn't see the performance gains I had hoped. As a result, I removed the indexes and tried a simple query to see what my ...
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68 views

MySQL DATE vs DATETIME read/write performace

Did anyone perform accurate read/write performance comparisons of MySQL's DATE vs DATETIME column types? Please do not bother writing "It should be faster" or "I think it's faster". I am looking for ...
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37 views

What is “good” single-block read latency?

Is there a reference anywhere that I can go and see what kind of single-block read latency I can expect from Oracle given a certain hardware configuration? I can run a query to show the current ...
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31 views

Optimal layout strategies for Time-Series using Columnar storage

In the context of time-series and specifically columnar storage systems. Question: What are the processes or heuristics that are used to determine how best the columns of contiguous values be grouped ...
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33 views

MySQL: What are the pros and cons of running with engine=Memory vs on a memory-mapped filesystem?

What is the difference (in terms of read and write perf, alter tables, backup and recoverability and consistency) of running a MySQL database on a memory-mapped filesystem vs with ENGINE=MEMORY
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22 views

Which benchmark assess string pattern matching in a database?

I have a postgresql DB in which I do a lot of string matching ala : UPDATE table1 SET colum1 = TRUE WHERE colum2 LIKE '%teststring%'; colum2 is a whole html file As I said I do A LOT of this and ...
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48 views

How do triggers work on partitioned tables?

I have partitioned a table on the basis of a column. This column can either have 0 or 1. So, only two partitions (p0, p1) have been created internally. On this table there are 3 triggers which execute ...
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34 views

Performance implications of mixing VARCHAR and CHAR fields in MySQL Table

I read the following answers in this forum: What is the performance impact of using CHAR vs VARCHAR on a fixed-size field? MySQL: Does the order of the fields in a table make a difference in ...
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40 views

Bulk update performance

I have a several process that aggregate some statistics on items (how much was shown, clicked ... around 30 factors). Once in a 5 minutes i flush the aggregate data to postgres (9.1). I have 250K ...
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86 views

How can I decrease FULLTEXT initialization time?

I'm trying to decrease execution time of the a query. Using SHOW PROFILE, FULLTEXT initialization takes about 0.3, which is too high. Other values are at normal level. How can I decrease FULLTEXT ...
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39 views

performance questions in database design

I need to describe a set of studies that are practiced to a patient, every patient have a "Clinical History", that are described in another table called "Clinical History Lines"(hclines) Every visit ...
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20 views

What is the optimal way to get a tabular view from an Entity-Attribute-Model table?

Following up on my previous question, I have created a table for storing measurements of different physical quantities. The schema looks like this: CREATE TABLE sensorreadings ( time TIMESTAMP, ...