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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Improving query performance involving similarity and full-text search

I have been trying to improving the performance of this query involving similarity and to_tsquery. I have a table (440,000 rows, PostgreSQL 9.5.2) with the following characteristics: test_db=> \d ...
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1answer
43 views

Performance schema: 'stage/sql/Sending data'

Background I am using MariaDB 10.0 but MySQL 5.6 answers are also of interest. Two machines cloned from the same image, same MariaDB configuration as far as I could tell, same dataset. One machine ...
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60 views

Suggestions for indexes or how to partition a table in SQL Server 2008R2

Table structure and DBMS SQL Server 2008 R2 I have a single table structure (flat) that has summarized sales data (YTD,MAT etc) by unique combinations of "Customer", "Product" and "Territory". ...
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64 views

MySQL: So many prepared statements in general log file

One of my clients complained serious performance issues in a web-application written in Java. I was suspecting that there might be some unoptimized queries which are causing the problem. I've enabled ...
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2answers
65 views

Filtered index error when using two column condition

I created a filtered index (in SQL Server 2012) and compared it with non-filtered index – I could see promising improvement as shown below. Now I need to change the filter condition to use two ...
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1answer
29 views

Speed benefits of Mysql Multiple Delete/Insert vs Select

I am working on a web application which involves a regular API call to the Amazon Product Advertising API. Given that Amazon limit the calls to one per second, I am looking at the fastest ways to ...
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1answer
66 views

Use of Trigger on table which can have 100 hits / second. Will it hamper performance?

Currently in one of our projects we have the following situation. The server computer is Windows Server 2008 Standard SP2. Processor is Xeon (R) 2.13 Ghz. We are running SQL Server 2008 R2. We need ...
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23 views

Performance Comparison using extended events

I am using SQL Server 2012. In my development database I have an old (MySP_Old) and new(MySP_New) versions of a stored procedure. This procedure has around 10 big queries in it. I need to compare each ...
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2answers
91 views

Filtering a result set on a very large table (using INCLUDE index in SQL Server)

Consider a very large table having hundreds of millions of rows defined as -- Here ObjectIdName and ObjectTypeName together are unique. -- Due to their size they aren't indexed, but rather they are --...
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87 views

MongoDB with multi core instance

I have a "large" EC2 instance with 2 cores running MongoDB as part of a Replicaset. Does MongoDB use both cores in parallel by default or do I need to make some configuration change?
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1answer
67 views

Hashed and heap indexed object storage table insert and query performance

This question is partly to ask advice and assure this design is sane. I state the the desired properties upfront here, then go in more detail in the rationale and follow up with the design and example ...
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2answers
62 views

SQL Server - SQL Plan Management for baseline

I am a .Net developer. I have a database upgrade coming up (from SQL Server 2005 to SQL Server 2012). The database team will be handling the migration. But I have seen forums posts saying that after ...
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60 views

sys.dm_db_index_physical_stats slow on first run after rebuilding indexes

I have a 10GB database in SQL Server 2016 RC1 on Windows Server 2012 R2 where I just performed many insert and delete operations. Afterwards, I ran: EXEC sp_MSforeachtable @command1="SET ...
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1answer
29 views

Performance penalty for using thousands of tables in MySQL

Background I'm using wordpress multisite in which each user will have separate blog. For each blog, additional 15 tables are created. The website will be used by thousands of users. That means that ...
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1answer
67 views

Database design for a lot of rows with data archive

i'm new to database design on larger scale. I have some knowledge and experience with MySQL but now i have some performance issues. Currently i'm using MySQL with 3 databases: History Snapshot ...
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1answer
33 views

MySQL BETWEEN command - performance (order)

I want to create a table which will contain approx 20,000 records of three fields each. Two of the fields will contain numeric values. I want to be able to issue a SELECT BETWEEN command. One record ...
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1answer
74 views

MySQL Explain gives different result for same query, query performance changes

I've been having some performance issues on my production server. The main issue, I think is the table pricelist_entries, which has approximately 6 million rows. Basically its holds all of the ...
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1answer
101 views

How do DTUs in Standard and Premium performance tiers in SQL Azure compare?

We recently observed a serious performance degradation in a SQL Azure database running in Standard3 performance tier - CPU utilization went from ten percent to fifty percent to almost one hundred ...
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1answer
156 views

Why is performance non-linear if I do many UPDATEs in a single transaction

An older question covers some reasons why the performance of multiple INSERTS within a single transaction is non-linear as the INSERT count grows. Following some of the advice there, I've been trying ...
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1answer
39 views

Select records not associated to a specific tag in a many-to-many relation

as shown in this sql-fiddle I have a bridge table events_tags representing a many-to-many between events and tags. I need the fastest way to find all events not associated to a given tag t. The ...
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3answers
68 views

IN Clause - listing values VS query

My app runs a lot of queries like this SELECT ... FROM Table WHERE CategoryID IN (SELECT CategoryID FROM OtherTable WHERE ..) To save performance I decided to cache the second subquery in the ...
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2answers
204 views

High latency with SQL Server 2014 Synchronous AlwaysOn

I've built a SQL 2014 cluster in our development environment that consists of 2 nodes. Non-Shared disks Specifications: Storage is Nimble Storage Array with dedicated LUN's presented to the ...
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41 views

MySQL Slows Down after MYD file reaches 2GB (64 Bit OS)

MySQL seems to be writing rows OK (75,000 rows/min) until when the MYD file reaches 1.8 GB, and then the insert rate drops immensly (10,000 rows/min), and 1 hour later it's even slower (6k rows /min). ...
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30 views

Bypass stored procedure execution CPU consumption

We are using Microsoft SQL Server Agent Jobs to execute stored procedures on the other database systems (like MySQL or Oracle). Usually we run procedures via linked servers (over OLEDB and ODBC ...
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2answers
482 views

Should we create a schema per “project”?

This is a database where users create a 'project' and work on it. We have a table for project and various other tables that contain different attributes for project (multiple rows for each project ...
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1answer
232 views

SQL Server on SAN, same LUN: one logical drive vs multiple

First, let me start by saying that I did notice there are multiple similar questions to this, but neither of them is exactly what I want to ask, and not one of them has a definite answer. Second, let ...
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2answers
56 views

Is there much difference between having a key (intA, intB), or having key (longAB) where longAB is the concatenation of bytes of intA and intB?

This is a bit of an odd question. Let's go with MySQL for example. I don't know a ton about db internals. Compare two scenarios, in one, we have a table with a composite key of the from (intA, intB)...
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131 views

Performance improvement by placing tables on a virtual RAM disk

I am trying to improve performance of queries by placing the tables in a virtual RAM DISK. I am using in Oracle 11.2 Standard edition with 4G of SGA and 2G of PGA. I created a Virtual RAM DISK of ...
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20 views

Load DATAINFILE extremely slow

I am using the code below to insert a 2.2MB file into a MySQL database in the cloud using Azure (the free version) with 36 thousand rows and 8 columns of doubles. MySqlCommand sqlCmd = new ...
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45 views

MySQL performance differences between two servers

I've a production server (CentOS 5.11) and a development one (Debian 8). Same MySQL version (but different architecture, i686 vs x86_64), same data, same config settings. If I execute a query with ...
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1answer
39 views

Which columns to index with LEFT JOIN and GROUP_CONCAT

So i have a complicated MySQL search query, and I wonder which columns I need to index to speed up searching: SELECT wpp.ID, post_title, wp_terms.name AS category, wp_terms.slug AS slug, ...
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4answers
135 views

Should I Denormalize Tables To Avoid Joins?

I'm in the process of developing a web application, and need some help with some basic db design. Currently, I am unsure of the following three tables: ### User ### - Id - DetailId - etc... (...
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2answers
45 views

Does subqueries “short-circuit” based on other conditions?

I have a slightly costly case when exists (...) then 1 else 0 end sub-query in the select clause. The sub-query is only really needed if another column in the main query has a specific value (can ...
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34 views

Accessing a row directly at a table in PostgreSQL by using the PostgreSQL's internal library

I am writing a PostgreSQL extension using the C language. I would like to do the following tasks: Store a set of rowids (or other row identifier, like ctid). Each rowid uniquely represents a row in ...
6
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2answers
174 views

SQL Server using index scan instead of seek when updating a view that has an INSTEAD OF UPDATE trigger via a cursor

I have a 3rd party application which uses a cursor that updates rows in my SQL Server 2014 table. I am unable to modify this code and have therefore devised a scheme to point the cursor to a view ...
5
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1answer
96 views

Sub-select takes “ages” - EXCEPT much faster

Script to create the tables DROP TABLE IF EXISTS history; CREATE TABLE history ( id integer NOT NULL, ticket_id integer NOT NULL); ALTER TABLE ONLY history ADD CONSTRAINT history_pkey PRIMARY ...
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1answer
32 views

InnoDB slow query (few derived and dependent queries)

I have a select query which always worked pretty fast but data kept increasing which is why this query became very slow (2/3mins). I need to get all 0 values from those tables in the last WHERE ...
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1answer
58 views

How to quantify rollback events in SQL Server between 2 dates

I need to quantify rollback events and find theirs reasons, without change the application code. There is any way to collect this data? The reason to check the rollback occurrences have need to ...
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2answers
69 views

Why could query performance improve enormous after db restore on new server with worse hardware?

A asp.net page doing very slow to load a list from SQL Server has increased it's performance very much after the whole database has been restored on a new SQL Server. The asp.net app has moved from ...
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3answers
113 views

Improve Restore Speed

I have a ~3GB backup file from our QA database, and a daily diff (~500MB). For data complexity reasons, some of our developers like to use regular backups from this database, and so we have a process ...
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3answers
80 views

Is having Estimated number of Rows > Actual Number of Rows an issue to worry about?

I've a table [order] where a simple select shows cardinal difference between Estimated Number of Rows and Actual Number of Rows and in a strange way. Generally Estimated Number of Rows skews as ...
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1answer
85 views

SSIS push and pull performance

After reading Which one is more efficient: select from linked server or insert into linked server? I wonder if this is true also for SSIS? For example, I have 2 SQL Servers (A and B) and SSIS ...
2
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1answer
84 views

Is this right decision to define 5-6 foreign key in a single table…?

If i define 5-6 foreign keys on a single table, are there any performance concerns? CREATE TABLE [dbo].[PS_CLASSROOM_MST]( [CLASS_ID] [int] NOT NULL, [CLASS_NAME] [varchar](50) NOT NULL, [...
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0answers
64 views

oracle : Effect of inserting new rows when row movement is enabled

I have a table which is partitioned by key. I want to move few records (which I require later) to another partition so that I can drop this partition and get some free space. I am enabling row ...
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0answers
47 views

Performance drops after online backup

We are using DB2 Express-C 10.5.5 on Ubuntu Server 12.04.5 64-bit. Every night we do a full online backup: backup db MYDB online to /home/db2inst1/backup compress include logs after backup we do log ...
3
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1answer
148 views

Speeding up a GROUP BY, HAVING COUNT query

I'm trying to speed up this query in Postgres 9.4: SELECT "groupingsFrameHash", COUNT(*) AS nb FROM "public"."zrac_c1e350bb-a7fc-4f6b-9f49-92dfd1873876" GROUP BY "groupingsFrameHash" HAVING COUNT(*) &...
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1answer
119 views

Why would a procedure sometimes hang executing SELECT…INTO #Temp2 FROM #Temp1 JOIN LocalTable…?

We have several stored procedures, called by jobs, that follow a specific pattern (designed to minimize blocking). Some of these procs tend to hang on occasion, running up the CPU, tempdb allocations, ...
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3answers
252 views

MySQL database uses too much CPU

I have a MySQL database which uses too much CPU. I am actually performing benchmarking to the web servers which queries the database. Right now the database is being the bottleneck, it uses too much ...
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1answer
67 views

If I query records matching some value, why does InnoDB examine most of the records that had that value once, but have changed since then?

We have an issue with MySQL InnoDB performance. We insert records into a table with a status field value of zero, these records need to be processed by another task. When this another task starts ...
22
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1answer
265 views

Very strange performance with an XML index

My question is based on this: Improve Xquery performance in SQL Server To give an answer there I did the following test-scenario. Test scenario First I create a test table and fill it with 100.000 ...