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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77 views

Best way to rank all the columns in a table and store those ranks in another table

I have SQL Server 2008 and a table w/ hundreds of thousands of records and about 50 columns. I run a sql statement like: Select rank() over(order by col1 desc) as Col1Rank, rank() over(order by ...
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1answer
44 views

Can the number of tables and functions affect performance? [closed]

I have some big database with hundreds of functions and tables. They also have a lot of sequences, custom types and some views and triggers. There is a point when the quantity of objects will be a ...
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0answers
38 views

SQL - Optimize table population with dynamic queries

I need to optimize the following pl/sql procedure. So, fundamentally my question is: There is a way you can do a bulk insert in a pl/sql that could be more efficient than loop through an associative ...
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1answer
129 views

Poor query performance due to recheck condition on index scan

We are testing the performance of metadata when stored in JSONB compared to a traditional EAV catalogue (commonly used in biomedical scenarios), using a PostgreSQL 9.4 server. I get a problem when ...
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1answer
363 views

SQL Server performance is slow when migrated from SQL Server 2012 to SQL Server 2014

We are trying to migrate from SQL Server 2012 to SQL Server 2014 on Windows 2012 R2 OS. After the upgrade, we are doing performance testing and observed huge difference in running a simple query from ...
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1answer
98 views

How can I improve this update?

I'm working with SQL Server 2014 Express edition and I want to upload some OpenStreetMaps data. Data is a 172 Mb XML and it loads ok. The problem is with this script: UPDATE ways SET geog4326 = ...
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0answers
26 views

PostgreSQL analyze only parent table only

I am moving data from a few billion records table to newly created partitions. I am inserting into the child table directly and deleting from the main table with filters on the appropriate columns in ...
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1answer
82 views

How to speed up mysql query against a 204 million record table

For some reason my server has been finicky lately and for the life of me I can't figure out why. I monitor the memory usage by running shell# watch -n 5 free -m without running any activities ...
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1answer
28 views

Requests to local CouchDB have 40ms latency

Requests to a CouchDB instance on the same machine have about 40ms latency when HTTP keepalive is used by the client, about 0-1ms latency when the client does not use keepalive. What causes this ...
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2answers
64 views

Max Degree Of Parallelism [closed]

What is the Best Practices for Enabling and Disabling the MaxDop Setting for SQL Server on regular basis. Is it ok to create a job and run the job as required or have the script stored as SP?
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2answers
63 views

Proportion of MySQL variables

I made some research on MySQL performance. After doing some tests and verifyed the improvement, (thank you guys) I end up asking myself: "Is there any formula or metric between groups of variables?" ...
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1answer
29 views

What is less time costly?

I'm migrating a database from DB2 to MySQL. There are big tables, so it takes a huge amount of time. The question here is: If there's a table with about 9 millions of records with InnoDB storage ...
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0answers
67 views

mysql eating RAM without queries?

Somehow MySQL eats up 50% of my RAM on the server being used. I checked and there are no queries, show full processlist is empty. I restarted the mysqld and within a couple of minutes the RAM usage ...
2
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1answer
41 views

How should a numeric value that is an external key be stored?

This is something I was pondering recently. trying to determine how to store certain values. The best wide spread example I can think of is Federal Employee Identification Number - more commonly knows ...
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0answers
32 views

PostgreSQL slow update -> does autovacuum have anything to do with it?

I am quite new to PostgreSQL as I only need it to create a map (using PostGIS). So I don't really know on hot how to optimise my DB... I have a table with a lot of polygons that I'd like to save in a ...
2
votes
1answer
134 views

Update taking too long

I am updating a table with 250 million rows in SQL Server, and it's been running for 4.5 days. I'd like to use the computer it's running on for other memory-intensive work, so I'm torn about whether ...
8
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1answer
693 views

Why adding SQL Server user to “Perform volume maintenance tasks” improves the speed of database resizing so much?

If I want to create 5GB database with CREATE DATABASE [test] CONTAINMENT = NONE ON PRIMARY ( NAME = N'test', FILENAME = N'E:\2012\test.mdf' , SIZE = 5529600KB , FILEGROWTH = 1024KB ) LOG ON ( ...
2
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1answer
204 views

PostgreSQL 9.x: a clustered index on column A is the same as creating a table ordered by A?

Reading the official PostgreSQL documentation for version 9.0 I read an interesting escamotage that performs better than CLUSTER for big tables: The CLUSTER command reorders the original table by ...
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1answer
45 views

How compiled are prepared statements?

I found this explanation of how prepared statements are compiled, but I'm still unsure. What exactly is "compiled" in the context of a prepared statement? Is a C compiler executed to create a custom ...
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2answers
64 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 ...
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1answer
58 views

Create database unique Surrogate Keys without using GUID’s

What is the best way to get database unique surrogate keys in Microsoft SQL Server when using something like “auto increment” as opposed to GUID's. The purpose is to increase performance over using ...
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0answers
52 views

Very high CPU caused by mysql service

A running mysql service uses CPU in a crazy way. (See attached screenshot from htop) I followed the instructions here with no luck. My server specs: CPU: 1900Mhz . Intel Hexa-Core Xeon E5-2420 ...
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0answers
168 views

Postgresql: Partition table by hour

I have a system that inserts several million records over the course of 24 hours. Users don't care about the data that's older than 24 hours, and typically query data over a small time frame (5 to 60 ...
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4answers
151 views

with MySQL, are multiple single column indexes faster than one multi-column index? [closed]

I have a performance related question, in MySQL, are multiple single column indexes faster than one multi-column index?
3
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1answer
149 views

Biggest wait WriteLog

I have been given a server (SQL Server 2008R2 64 bit) where our application is running. There has been a gradual decrease in the performance of the application. Now it has come to a point where ...
0
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1answer
69 views

Best query to exclude existing friends from query

I have a User table / id_user / username / .. friends table (pair AB and BA): / friend_of / friend_to and a friend_request table (used for pending friend requests) / id_req/ sent_from / sent_to ...
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2answers
143 views

Make DB tables customizable from an Admin

I want to build an commercial product promotional mobile application in which the administrator of the app will be able to customize some texts / pictures or whatever from the database that ...
4
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1answer
72 views

What is the performance impact of queries against DM objects using DMVs in SQL Server 2008?

Recently, I've been running queries against our production system on the DMVs for querying the plan cache. In particular, here's the from clause of the query: FROM sys.dm_exec_cached_plans AS cp ...
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1answer
81 views

Get statistics of slow running queries

My database application runs many different queries. I have set log_min_duration_statement to 1000. But queries logged there are not always slow, most times they just take a few ms. Is it possible to ...
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1answer
59 views

Query optimization and takes less execution time

CASE-1: SELECT * FROM A JOIN B ON B.CustomerID=A.CustomerID CASE-2: SELECT * FROM A JOIN (SELECT * FROM B) C ON C.CustomerID =A.CustomerID Which CASE is efficient ?
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2answers
76 views

Best database for a real time application [closed]

I am a student doing my Final Year Project where I need to build an android application for on the road navigation. The problem is the application has a feature that alerts the user of nearby incoming ...
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1answer
52 views

How to define the table structure for measured data in sqlite

I have an embedded system with an sqlite database. How should I define the table structure for the measured data from 4 sensors? Each sensor give us every second an numeric measured value. The ...
2
votes
0answers
32 views

Performance of bitwise operators on byte column vs individual bit columns

I'm designing a database schema at the moment, but have a performance query. Our table needs to have (at least) two flags, or boolean values. We can call these IsComplete and IsExportable. The ...
0
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1answer
63 views

Slow ranking values in MySQL

I have a table of around 30 million retail products, with various INT columns that describe sales counters and pricing at different retailers. I'm supposed to display well over 70 different rankings ...
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0answers
96 views

Database performs differently on the two same Xeon E3 1270-v3 Quad Core machines [closed]

Configuration: RAM: 16 GB DDR3. HDD: Seagate 500 GB 7200 3Gb/s 3.5 inch SATA - idential disks. Postgres 9.4, tried with 9.4.1 also Windows 2008 R2 Web Tried these tunings: work_mem = 32MB ...
2
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1answer
112 views

Indexing nvarchar(128) in SQL Server

Have no idea how indexing works in SQL Server. Working with a SQL Server 2012 Intel Xeon 2.2 GHz dual core 8 GB RAM. Will indexing a nvarchar(128) in addition to int primary key cause any ...
3
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0answers
181 views

Slow transactions, many locks

At high load conditions the server app stops responding to client because begin/commit statements are executing very slowly (some take 15 seconds). The queries are simple - insert, update two columns ...
3
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1answer
175 views

Is a clustered index on a child table in a parent/child relationship the most optimal index?

A clustered index will sort row data in a table according to the ordering of the fields in the index. If so, why would you (or would you not) want to create a clustered index on the child table in a ...
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2answers
38 views

Is it a good idea to add a reserved field to a large MySQL table?

As you may know adding a new column to a MySQL table with millions of records is hard and in some cases impossible. Is it a good idea to add a text column to each table (say, meta) to save some ...
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2answers
251 views

Improve performance of converting a large xml file (~300 MB) to relational table in SQL Server

So this is what I have so far: --Read xml content into a XML data type variable DECLARE @FileData XML SELECT @FileData = CONVERT(XML, BulkColumn) FROM OPENROWSET(BULK '\\file_path\test.xml', ...
1
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1answer
60 views

Does the length of the index name have any performance impact?

This may seem silly, but in trying to stick to my standard nomenclature when naming indexes in our DB, the latest one was a little lengthy, and like all things DB I wondered if it in any way could ...
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2answers
49 views

MySQL Image Queries

I have table employees in MySql database with Id, Name, Gender, HireDate, Photo. Photo field is blob. Now when I run this query: SELECT id FROM employees WHERE Photo IS NULL ; it takes forever to ...
0
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1answer
73 views

Application is hanging when database upgraded from SQL Server 2000 to SQL Server 2008 R2

Presently we are working with SQL Server 2000, the database is perfectly working with our software for retail sales counter application developed with VB 6.0. But after upgraded to SQL Server 2008 R2, ...
0
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1answer
153 views

MySQL always writes simple temporary/memory tables to disk (both tmp_table_size and max_heap_table_size are set to 8GB)

I'm struggling with this issue and just can't figure out why this is happening. CREATE TABLE sitecache._test ENGINE=MEMORY SELECT * FROM website.gallery_likes WHERE 1=0; Every time I execute this ...
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1answer
256 views

Non-sequential Primary Key performance in PostgreSQL 9.3

Due to requirement to support distributed environment, each of my clients has been assigned unique node id, it appends the node id with running number as primary key and stores at local database. E.g. ...
6
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0answers
211 views

Timestamp-based index

I have a big database (200GB+) that contains some log info. And I want to speed up SELECT queries and stored procedures. I have a table with a GeneratedOnUtc datetime column, and have a non-clustered ...
0
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0answers
42 views

redshift performance effect if use 32 character long unique string as Primary key instead of auto incremented int

In my analytics application I am creating 32 char long unique string for each hit as user_session. In current implementation, I am storing user_session in tbl_sesssion in session column and I am ...
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2answers
25 views

Can I extrapolate from the progress reporting in MyISAM ALTER?

I'm migrating a 300 million row MyISAM table to add some indexes. Just because it might be relevant, here's my ALTER statement: ALTER TABLE my_table ADD UNIQUE INDEX my_table_abcd (a, b, c, d), ...
2
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1answer
106 views

Oracle 11g connect overhead

Currently one of our new applications is connecting to an Oracle 11g instance over 30,000 daily (at every user request) via their application server, using the same account. (it will be significantly ...
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0answers
57 views

Multiple subqueries performance issue

I have a query that collects customer data. I select a lot of correlated data from different tables. I want to have only ONE result row for each customer. The query looks like that: SELECT c.Id ...