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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VARCHAR primary key - MySQL

Currently, I have a categories table with 2 columns - category VARCHAR(50) NOT NULL PRIMARY KEY and parent VARCHAR(50). The parent column is a foreign key (FK) to the category column. This seems like ...
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2answers
157 views

novice-design: Are FOREIGN KEYs always necessary? Joins on columns which are not PK

I've been wondering if following approach is bad or really very bad:). Question#1: can we use indicator_id to combine data from indicator_values and indicator_details tables (without using FOREIGN ...
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0answers
92 views

MySQL 5.6 Performance Tuning Issue

I have read and try lots of things about MySQL optimization and tuning. I tried most of them one by one according to our needs but nearly I got nothing. I am doing my test using some simulation ...
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4answers
33k views

When a previously-fast SQL query starts running slow, where do I look to find the source of the issue?

Background I have a query running against SQL Server 2008 R2 that joins and/or left-joins about 12 different "tables". The database is fairly large with many tables over 50 million rows and about 300 ...
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0answers
56 views

How can I restore a MySQL dump faster on Windows?

I am restoring some InnoDB and MyISAM .sql files that are on the order of GBs (ranging from 1 GB to ~ 10GBs) and they are taking a day or longer to restore. The command I am using currently is: use ...
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18 views

Reliability of MySQL Events Table

Is there any limitation of usage of MySQL Events table. Let us say i will have 10K of entries which will be executed across 3k schemas. They all are not same time but at-least 3K events will be ...
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1answer
7k views

Why does MySQL (InnoDB) table get faster after OPTIMIZE TABLE, but then don't work?

I have a Django web application that stores data in a MySQL InnoDB database. There is a particular page that is accessed a lot on the django admin, and the query is taking a long time (~20 seconds). ...
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4answers
606 views

Does updating a row with the same value actually update the row?

I have a performance-related question. Let's say I have a user with first name Michael. Take the following query: UPDATE users SET first_name = 'Michael' WHERE users.id = 123 Will the query ...
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2answers
58 views

Un-optimize a MySQL database?

I want to run ANALYZE TABLE and OPTIMIZE TABLE on a large production MySQL database (v 5.0) to increase performance. But as this would lock tables causing downtime for an unknown amount of time, I ...
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1answer
229 views

PostgreSQL performance worse when adding CPUs

I ran into a strange behaviour when benchmarking PostgreSQL. The setup is like this: Virtual box VM, with 3 GB of RAM. The host has 16GB of RAM and 4 CPUs. Ubuntu 14.04, standard PostgreSQL 9.3 ...
5
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1answer
67 views

Measure Performance for INSERT, UPDATE and DELETE commands on DB2

I have a DB2 database with a table for daily transactions, which is cleared to a history table at the end of the day, every day. I insert rows to this table via java-JDBC INSERT commands and they ...
5
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3answers
5k views

Frequently slow queries while in the 'Update' state

I have two tables that I update very frequently, one with a direct UPDATE .. and another INSERT .. ON DUPLICATE KEY UPDATE ... Normally these queries are instant but at times will take 0.1s to 1+ ...
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1answer
140 views

Automatic migration failed on Azure Database

I am using Entity Framework 6.1.1. The database has three million records; migration has to change the precision of a column of type decimal. The migration timeout window is set to the maximum value, ...
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4answers
171 views

Should I normalize my string arrays, or just keep it a simple string?

I am working on a project involving cards from the Magic: The Gathering game. To be of any use, I must load the basic information about each card into my database, but some of the fields may contain ...
12
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3answers
9k views

Should I add an arbitrary length limit to VARCHAR columns?

According to PostgreSQL's docs, there's no performance difference between VARCHAR, VARCHAR(n) and TEXT. Should I add an arbitrary length limit to a name or address column? Edit: Not a dupe of Would ...
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4answers
403 views

Is there any scenario where the existence of one or more Indexes in a table can prejudice it?

The title sums it up. I've learned and always heard that indexes in tables improve CRUD operations. A developer that I met last weekend told me that he does not like Indexes because they are bad - ...
8
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3answers
223 views

Application querying empty tables

My company uses an application which has pretty major performance issues. There are a number of problems with the database itself which I am in the process of working through, but many of the problems ...
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1answer
49 views

Best way of order processing

I would like to write a procedure for order processing Single Order can have multiple items, how can I process the order ? Consider below JSON is an example: { "Order": { ...
8
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2answers
40k views

SELECTing multiple columns through a subquery

I am trying to SELECT 2 columns from the subquery in the following query, but unable to do so. Tried creating alias table, but still couldn't get them. SELECT DISTINCT petid, userid, (SELECT ...
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1answer
51 views

sqlite database table with 1000's of columns

I am using sqlite3 in an application to conduct an alalysis of distances between sets of points. Distances between these points have been precomputed using dijkstra's algorithim and left me with a ...
1
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1answer
158 views

Print, transaction and cursor performance in Transact-sql

I'm having some performance issues when I run a script. I was reading about the problem with print and its performance, but I cannot figure out how to reduce the impact. The algorithm is O(n^2). The ...
1
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1answer
117 views

Vertica performance on select from view with union

We have a huge number of rows(tens of millions), and for each table we have an associated view that is a select with UNION ALL between that table and several others. Now, we are doing a select from ...
6
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1answer
137 views

What is more appropriate sp_updatestats or UPDATE STATISTICS?

In a system there is a nightly data load process where all the foreign keys are dropped, all tables are truncated, repopulated from an external source, and the foreign keys are put back in place. At ...
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0answers
50 views

MySQL performance issue after migration

I have a MySQL performance issue with a brand new server, and am somewhat of a beginner as a database administrator (I'm mostly a general-purpose Linux sysadmin). I'm looking for pointers where to ...
8
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1answer
20k views

High Buffer I/O SQL Server 2008 R2 causes?

Am trying to troubleshoot performance on an SQL server that we have for our document management server and today performance has hit an all time low. Looking at the MDW I setup recently I can see a ...
0
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1answer
27 views

Perfmon Counters that relate to SQLIO

I am trying to benchmark a new virtual SQL server. this will be the first time I have virtualized a production SQL server. I don't think this is a supper busy server. 100-200 users, of varying ...
5
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3answers
398 views

Warning about implicit convert

I have table with 2 name columns: CREATE TABLE Test ( TestID int identity primary key clustered , Name_Eng nvarchar(50) , Name_Nat nvarchar(50) ) Now I need a query to get this Name column ...
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0answers
22 views

PostgreSQL: Improve system performance, KNN modification with GiST Index

In my PostgreSQL 9.5beta2, Postgis 2.2.0 compiled by Visual C++ build 1800, 64-bit I am running a Nearest-Neighbor-Query with the additional complication of unique assignment. I am running this on ...
7
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4answers
934 views

DDL contention on TempDB

I have a SQL Server 2005 Standard x64 that is experiencing issues with TempDB DDL contention for the past few months. The server will experiencing contention on wait resource 2:1:103 (the wait type ...
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1answer
29 views

Update all rows when sort/ordering value is changed for single row?

I am in the process of creating a GIS application with multiple layers and many pieces of content shapes on each layer. Currently each layer/shape is drawn in the order that it was returned from the ...
0
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1answer
60 views

AWS EBS I/O Bottleneck

I'm hoping someone can help me understand some EBS Bottlenecks that we are experiencing with a new Windows SQL Server instance we're configuring. We're running some tests by conducting a full backup ...
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0answers
19 views

MySQL 5.6.18 got signal 11

My MySQL Server 5.6.18 got signal 11 today very randomly. Has not happened before. This is the stack trace : stack_bottom = 7fdb9bcb1e0f thread_stack 0x40000 ...
20
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2answers
908 views

IF EXISTS taking longer than embedded select statement

When I run the following code it takes 22.5 minutes and does 106million reads. However, if I run just the inner select statement by itself it only takes 15 seconds and does 264k reads. As a side note, ...
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0answers
42 views

SQL Server 2012 AG replication issues

We just went away from SQL Serer clusters in SQL Server 2008 to SQL Server 2012 with AG – have five servers with replicas in a secondary datacenter and syncing over a dedicated eline/LAN layer 2 ...
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3answers
760 views

Create function in central database or repeat in each database?

One of my developers has written a SQL function that works like the VB.Net function (LastIndexOf) and wants to publish it. My question is what would be the reason to put this in a central database ...
45
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5answers
48k views

Pattern matching with LIKE, SIMILAR TO or regular expressions in PostgreSQL

I had to write a simple query where I go looking for people's name that start with a B or a D : SELECT s.name FROM spelers s WHERE s.name LIKE 'B%' OR s.name LIKE 'D%' ORDER BY 1 I was wondering ...
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0answers
61 views

How to optimize this query on oracle?

I have built this query in oracle to get some data i need from the two tables below. At SELECT REGEXP_REPLACE i get the IN_01 as input parameters from the user and it can be much bigger list than ...
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1answer
87 views

Index performance for CHAR vs VARCHAR (Postgres)

In this answer (http://stackoverflow.com/questions/517579/strings-as-primary-keys-in-sql-database) a single remark caught my eye: Also keep in mind that there's often a very big difference between ...
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1answer
23 views

Application load considerations, use what you get vs. not all at once

General question: Should I as an application use all resources I can get and thrust the OS schedeuler or should I already do some load considerations for the OS. If so, what metric should I use? ...
2
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1answer
81 views

Disk I/O Utilization at 95%

My disk I/O utilization is at 95% at my MySQL server. What are steps I could take to fix this? It is a Ubuntu VP with 16 GB Memory and 8 cores. Here is a screen-shot of the load:
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0answers
47 views

Linked Server to Oracle seems to be slow

we have a linked server between a SQL Server 2008 R2 instance and an Oracle 11.1.0.7 instance using OraOLEDB.Oracle Provider. The enabled options for provider are: Dynamic parameter Nested queries ...
1
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1answer
57 views

Which database should I look at for analyzing ~30gb, 700M records dataset?

I'm looking at analyzing a kaggle dataset which is pretty normalized, specifically joining, grouping, slicing and dicing the 3 tables patients(2M) <-> diagnosis(700M) <-> doctors(2M). I ...
2
votes
1answer
58 views

Primary key addition for a table which contatins no data is too slow

We are using mysql. We are running 10 alter queries which contains 3 Primary key deletion and 4 column addition and 3 primary key addition. And this alter query is on three tables which don't contain ...
1
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1answer
2k views

Production SQL Server High CPU for a Single Query

I have a single query which is consuming a larger amount of CPU than I would expect in SQL 2008. I am not able to determine why the CPU is spiking for this single query. I can trigger an ...
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0answers
38 views

Database calculations question

I am creating a MySQL database that is going to be used to store a lot of timestamps. There are currently 6 timestamp fields that data can be entered for one row. I am utilizing timestampdiff to ...
5
votes
3answers
2k views

Some book suggestions for performance tuning

I am in the process of improving performance on our database application. While I am not a DBA, I am pretty comfortable with SQL. I am after a book that can help me understand how queries written in ...
4
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2answers
229 views

SQLServer:Buffer Cache Hit ratio is a good indication of POSSIBLE memory bottleneck?

I am looking for an indication (if any) that would either disregard the memory bottleneck option, or accept it, or make me investigate further. for instance: page life expectancy: SELECT ...
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1answer
39 views

Is there an actual problem in my storage IO or is the data incorrect?

Running SP_Blitz indicated that I have a slow read/write performance on my drives. Reading further, I eventually landed on this query to view the actual statistics of IO occurring on my drives: ...
4
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2answers
2k views

SSRS Blocking Processes

We have a busy SSRS Reporting server (SQL Server 2008 R2) on which we see frequent blocking between the below processes: [dbo].[CheckSessionLock] [dbo].[WriteLockSession] We are aware that some ...
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0answers
39 views

Procedure taking so much time [closed]

Can anyone help me out. This is first time im working on performance tuning can anyone help me out. If want i can paste the proc also.