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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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MySQL Performance vs. Memory

We are running MySQL Ver 5.7.18 on an Amazon Lightsail Linux instance (2GHz Single Core CPU, 2GB RAM, 40GB SSD). Besides MySQL, we also run some Java services on this machine, which access the ...
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15 views

Avoid performance bottlenecks in a heavily locked table

Let's say we're designing a relational database for a bank. We have a Transaction table that holds each financial transaction and an Account table that holds information about a bank account, it will ...
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14 views

DB2 Workfile scan

We just migrate from LUW to zos and we're finding that in z/os the accesspath explains show new node named WFSCAN (Workfile scan) and this rises when there is a join, group by or any kind of sort. ...
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24 views

Why should I save both markdown and the converted HTML in my database?

First of all, forgive me if this is the wrong place to ask this or if this has been answered somewhere and I just can't seem to find it. So you have a scenario where you have an article/news web app ...
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26 views

Enabling TDE on PRODUCTION Servers - Guidance , Suggestions and Testing TDE ways

First of all just want to say , I am completely new to Transparent Data Encryption. Can I get some guidance on things to keep in mind while I am enabling TDE on Critical PRODUCTION Servers. I have ...
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35 views

Query performance diffrence between equals and between

I need to know why the correct answer is D ? what is the diffrence between D and A. Your database contains a table named SalesOrders. The table includes a DATETIME column named OrderTime that stores ...
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47 views

Oracle Top CPU Consuming SQL is “select longdbcs from javasnm$ where short = :1”

For the Oracle 12c database I've been administrating, I usually carry out the monitoring using Oracle Enterprise Manager Cloud Control 13c. From time to time, the database suffers from performance ...
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42 views

Queue Depth and vSCSI controllers

We have a purestorage san, a couple of VMhosts each serving up several SQL Server VM's. Each VMhost is given a slice of the SAN and each SQL Server VM is presented a single data VMDK and a single log ...
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45 views

Performance Tuning ETL

I administer a datawarehouse running on SQL Server 2016. This datawarehouse has most of its ETL processing done during a nightly load, except for a few SSIS packages that run throughout the day, then ...
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2answers
89 views

Will Re-Seeding an Identity column back to 0 cause page splits?

Simple table with an identity table as a clustered primary key. We unexpectedly hit the max value for the column, so I requested our DBA re-seed the table back to 0 to give us some time to examine ...
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1answer
57 views

SQL Server Version Store Performance differences between RCS and ASI

I understand that Read Committed Snapshot (RCS) operates at statement level, and Allow Snapshot Isolation (ASI) operates at transaction level, and both store row versions in tempdb. I also understand ...
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2answers
68 views

Performance problem with big query on first run

I'm having a problem with a query usually being so slow on first time run that it times out and then executing in under a second once it's loaded into cache. The query looks something like this exec ...
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Coffee shop static tag/attribute querying (satisfying AND & OR condition groups) - Relational DB/DBMS or NoSQL?

Let's say you are storing information about coffee shops, and you want to assign an arbitrary number/assortment of static tags/labels to each cafe which act like attributes (i.e., the cafe either has ...
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17 views

Performance: Joining small table onto large table vs generating into large table

I'll start with an apology, I don't quite know the correct terminology, so please feel free to edit my question. My real goal is to create a 'variable' that I can use multiple times. This is what I'...
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19 views

Polling Change Tracking on SQL Server 2016 - Performance

I am currently designing an event publisher to a service bus with the intent of using change tracking tables as the source, loading the changes into a separate table, and marking them as processed ...
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1answer
64 views

Spike and time out errors every x th minute

I have very complicated situation here. Application team was reporting that they see spikes and errors every 20 mins. We checked what was running and found log backups. So we tuned log backups using ...
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32 views

Tracking parameter passed to Stored procedure - extended events

I am trying to track a slow performing SQL and I am trying to capture the parameters that are passed in for the slow runs. I am tracing module_end and rpc_completed. The stored procedure is run as ...
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1answer
27 views

Enabling TDE on SQL Server AOAG 2014 Databases - Guidance

I am completely new to Transparent Data encryption and please help me on below questions related to enabling the TDE on existing PRODUCTION Databases. Primary Question: What are the things which I ...
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2answers
148 views

SAN IOPS figure

Recently we've been having high disk latency issue and wanted to benchmark one of our mount points on a preprod server to get an idea of how much IOPS, Throughput and latency our SAN is capable of. ...
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1answer
35 views

Difference between fetched and returned tuples in postgresql

I'm facing a hard time trying to figure it out some performance problems in my database. I'm using a bunch of resources online to learn what to monitor and how to interpret that information. From ...
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2answers
51 views

Functions causing Serial plan.What to use instead? [closed]

I have few stored procedures in my SQL Server database.I see that these stored procedures are running in serial mode from their execution plan. For example : CREATE PROCEDURE [dbo].[DemoProc] @...
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1answer
47 views

MySQL creates tables very slow

On my home machine running Ubuntu 18.04 and MySQL version 8.0.12 with better hardware, table creation, database creation and so on are very slow. On my other computer with older hardware (slower SSD), ...
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1answer
488 views

Why doesn't SQL Server have any missing index requests in the DMVs or Query Plans?

I have a SQL Server database where the queries are pretty slow, and there's a lot of locking and blocking. When I look at the missing index DMVs and query plans, there aren't any suggestions. Why ...
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51 views

Is it harmful to update columns which aren't changed?

Say I have a table with some columns: CREATE TABLE t ( key int PRIMARY KEY, c1 int, c2 text, c3 timestamptz ); I now fetch a row from the table: SELECT * FROM t WHERE id = 180; ...
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1answer
31 views

Performance: ALTER TABLE with default value vs. iterating over all records to set new value [closed]

For adding values to a new column, I have the following options: Using default to add value during ALTER TABLE command. Doing ALTER TABLE without default, then fetching all the records and iterating ...
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1answer
45 views

Insert into table with identity insert taking almost a second

We have an oltp application and I am trying to troubleshoot why insert into one of our table is taking close to a second. Not all inserts are taking this much time but there are some which does take ...
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1answer
21 views

Mysql sudden high disk usage when connections increased

recently we had an incident where because of a slowdown in an external service, the number of processes on the web server increased a lot. This caused mysql to reach max connections. However, the ...
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1answer
37 views

Merging these two tables is a good idea?

i have those tables names hobbies names_hobbies | id | name | | id | hobby | | name_id | hobby_id | |----|----------| |----|-------------| |--...
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17 views

Query that fetchs average values over timestamp range of time, on a certain value of another pair of fields

This is the situation, over the time our table reached around 800 millions rows. And it is going to get bigger and bigger. It is a service that collects metrics of energy (voltage, power, current, etc)...
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20 views

Database that supports tracking of owner, timestamps and source for every field?

We have to build a database that allows us to track a set of entities and their relationships along different dimensions: Owner: so that we can obtain the pieces of data that a specific owner can see....
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6 views

Handling Many Text Fields in a Mysql Table

Specification : Mysql (5.7.23) , Baracuda file format, DYNAMIC row format. I am working in bootstrapping a product. I have a scenario where the user may require 1 - 500 Text Fields for a particular ...
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38 views

6 million shared buffer hit, is that a good thing? [closed]

I have a query which takes around 17 seconds to complete. Here's the EXPLAIN (analyze, buffers): The main part in text is here "-> Index Scan using responses_form on responses (cost=0.55.....
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Building friendship relatationship in mysql

I am creating friendship between user A and user B. So far my table looks like this: friendship_request | key:send_user | key:recv_user | sent | friendship_request_history | send_user | recv_user | ...
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27 views

Duplicate values in “IN” expression

My query looks like SELECT * FROM table WHERE id IN(2,5,6,6,9....) The "IN" expression may include thousands of ids, which may be duplicated. Is it affects on performance, or I should clean the ids ...
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31 views

SSMS Execution Plan Index Suggestions

I am trying to differentiate between performance when I have non clustered index on certain columns and, when it isnt there. For example: I have a table named Employee and following columns: ID (PK,...
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27 views

Azure's New Tiers (2018) - Standard vs Premium

We've done what we can to index things intelligently, but we're beginning to scale up our database usage and have decided scale up (?) from Azure's S4 tier to P1. It looks like P1 has fewer DTUs and ...
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38 views

Database Design - Meal (Combo) with multiple customizable items

I am working on a project where a customer is able to customize his/her combo meal that contains multiple customizable food items. I have created a "Meal" table joined with "Items" so that multiple ...
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137 views

Performance problems after setting ALLOW_SNAPSHOT_ISOLATION on

I'm running a 15GB database on SQL Server 12.0.5207. Server is a virtualized Windows Server 2012 R2 with 16GB RAM and 4 CPUs. Yesterday, we set ALLOW_SNAPSHOT_ISOLATION to ON, to check if it would ...
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1answer
27 views

How to speed up execution time in a SQL Server 2016 database which has restored from 2008 R2? [closed]

I have restored the backup of the database from SQL Server 2008 R2 to SQL Server 2016 and now facing the performance issue. How can the issue be solved without changing database Compatibility?
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59 views

Is SQL Server on Mac equally well performing as it is on Windows?

My friend decided to learn SQL Server and T-SQL. However, he has a Mac machine. It is my understanding that SQL Server's primary use case was to be run on Windows. What potential issues may he run ...
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19 views

Perfmon Counter stop collecting at random Intervals

I have created a collector set in Windows Performance Monitor which logs to a SQL table using an ODBC connection. The collector set runs everyday from 00:00 and starts polling and stops polling for ...
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17 views

Recursive search and sharding

Our application collect logs and writes them into PostgreSQL database. Currently each client has a separate database deployed on client's machines. But we want to make it "software as a service", ...
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2answers
262 views

Inserts in MySQL 8 are slower than Inserts in MySQL 5.7

I've started to use MySQL 8 (8.0.12), and I'm realizing that the "inserts" are slower in this version than MySQL 5.6 or MySQL 5.7. It doesn't matter if the table is MyISAM or InnoDB, with just one "...
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30 views

Automating performance tests in PostgreSQL

I want to check the performance of specific queries in a Postgres database on a regular basis. Also, I want to be able to check the change in performance of different queries with any change in my ...
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29 views

Service Broker process active for too long in SQL Sever

Let me acknowledge, I don't know much about database efficiency neither Service Broker as a whole, where I work the dba that used tp handle these kind of things left some weeks ago. The company uses ...
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1answer
22 views

Query takes too long to query with OR clause but their parts are very quick

I have two tables with ~1M rows indexed by their Id's. the fallowing query... SELECT t.* FROM transactions t INNER JOIN integration it ON it.id_trans = t.id_trans WHERE t.id_trans = '5440073' OR it....
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51 views

Stuck at optimizing “not in clause” for a medium-sized query across two tables

I have a system to teach English. For each word someone learns, I record: LearnedWords -- Id -- UserId -- WordId And for each new text that I give to a learner, I want to indicate what ...
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71 views

Poor performance when joining on subselect

Edit 3 (additional explanation and improved table aliases) A computer system is used to control the sales of multiple products across multiple online stores. Each store has a selection of shipment ...
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66 views

How to do a fast simple query on a large table of postcodes

I have a table with 2.5 Millions of Postcodes. I have to populate a textbox while the user is searching for the Postcode so the query has to be very fast. The table is composed by: ID (Primary key)...
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Best Indexing for Performance - MySQL

I have a question related performance DB MySQL. I have querying like this with big data inside : SELECT * FROM tableA a INNER JOIN tableB b ON a.id = b.id AND a.code = b.code ...