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 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
35 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
125 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
44 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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0answers
33 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 ...
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2answers
169 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 ...
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1answer
94 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
51 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
67 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
105 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
63 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 ...
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1answer
83 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
56 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
46 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 ...
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1answer
130 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
115 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
222 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
66 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
203 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 ...
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1answer
97 views

Why Write IOPS,Write throughput,Queue depth decreased on AWS/RDS after changing innodb_flush_log_at_trx_commit and sync_binlog?

I changed values for my Mysql parameters 1. innodb_flush_log_at_trx_commit=2(before it was 1) 2. sync_binlog=0(before it was 1) This has changed some of my parameters on AW RDS drastically ,here ...
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0answers
24 views

Is joining two tables from the same DB faster than in separate DBs? [duplicate]

Would a query / view for joining two tables that reside in the same DB perform faster than one table from each DB in the same instance? I'm using SQL Server 2008 R2 and it's a simple inner join.
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2answers
89 views

Regarding difference in execution time of queries

These are two explain plans of two different queries that return the same results but at a drastically different speed (280 second vs 1-7 seconds). I want some help knowing what the fast query has so ...
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1answer
100 views

How do I get useful SQL Server database performance statistics?

We currently have several shared SQL Server servers and instances in our organization. They are going with a different architecture where business units will get their own SQL Server instances. We ...
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26 views

select aggregates at each funnel step

I'm trying to find a way to efficiently get aggregates at different stages of a funnel. For example, given documents that contain sections, I want to tell how many sections and documents an author has ...
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0answers
43 views

SQL Server 2012 Express and Hardware Differences affecting performance [closed]

Here is the setup. I'm running SQL Server 2012 Express on the following two boxes: Box 1 (Server) : Dell T710 2x X5680 3.33Ghz Xeon 92GB Memory RAID 10 - 146GB Dell drives, w/ Cachecade SSD drive ...
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1answer
40 views

Strategy To Remove Old Records

We are running Oracle 11.2.0.4.0. It is a transactional database that has been online since 2011. We have been tasked to clean up old records. The table structure is (parent->child): A->B-C->D->E ...
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1answer
60 views

PostgreSQL takes 99,9% I/O? [closed]

Please, look at this screenshot of iotop tool output (Linux). There is long-running batch update process on table with 20+ million rows. Does it mean that postgres is limited by I/O disk performance?
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0answers
77 views

Adding a Mongo Shard decreases the insert performance

For a mobile application which will hold quite some documents, we've chosen Mongo as a database. Let me explain the situation first: Every day, I have a set of documents that needs to be inserted, ...
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0answers
46 views

How to compare different DBMS? [closed]

I'm planning to compare MS SQL Server and Teradata. I know, they are have completely different architecture, because they were created to achieve different goals. But here we are. I have generated ...
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83 views

Very slow MySQL performance

I have 4 million rows in MySQL. I have a count query to fetch from DB to Apache web server. The issue is first load (Count query) - when I click fetch button, it takes more than 5 mins. Second time ...
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0answers
58 views

Read READ COMMITED transaction advantage in MySQL, high performance object model

I am writing high performance object model with READ COMMITED locking. My question is if there is any reason to starting READ ONLY transaction for read only operations vs. standard SELECT not ...
5
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2answers
176 views

Total billions of rows and daily millions of row insert: What database system suits best [closed]

We developed a system with very high volume of data but very simplified data structure. We had only cellX, cellY, timeStamp and value columns. Operations are: Insert 455+ thousand rows per day ...
4
votes
1answer
106 views

Debug query on big table that is sometimes slow

I have a web API that is backed by a Postgres database, and the performance is generally very good. I monitor the performance of both the database and the application as a whole. Most of my queries (...
2
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1answer
88 views

MySQL best performance settings [closed]

I am going to do some performance tests on MySQL server as I want to evaluate how MySQL behaves in some situations. MySQL is the only (additional) software installed on my server (Windows Server 2012),...
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0answers
87 views

Sort operation SQL Server 2012

I am trying to optimize a query and the sort operation (91% cost) is the costliest operation. Any help will be appreciated. Query is : SELECT TOP 1 ArchiveType, CONVERT(NVARCHAR(30), A....
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0answers
29 views

One bitmask column vs multiple bit columns [duplicate]

I have many tables with a column storing a set of days of week. I used to use MySQL and data type "set" worked well. For example: [worker] id weekday_mask (data type: SET('Mo','Tu','We','Th','Fr','Sa'...
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3answers
306 views

Count is slow Oracle

this is my query : SELECT Count(last_upd) FROM S_CONTACT WHERE last_upd_by = '0-1' AND LAST_NAME <> 'Wait' AND last_upd + 1/24 > SYSDATE - (1 / (24 * 60)); It takes 84 seconds to return ...
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6answers
927 views

Fast reads without paying the price on writes

We have a large append-only table containing financial transactions. On average 1000 transactions are inserted per minute. Since there are now more and more usecases where we actually want to read, ...
3
votes
1answer
120 views

Improve performance of query with multiple group by column and count function in select

Brief Background of issue We have a aggregate table to store activities of competitors and this table have currently 3 Million activities and we need to retrieve data from this table group by ...
0
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1answer
93 views

Does innodb_buffer_pool_size accept “*GB” values?

I thinks innodb_buffer_pool_size is specified in bytes, would typing in values with unit (i.e 1024MB or 1GB) work? Has anyone already tried this? Specs: MySQL 5.6
1
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0answers
50 views

Disable/Remove Table Index for INSERT Performance

I am doing a database maintenance where I have to add new fields to a table with over 10GB of data about (20 million rows). To solve that I renamed tableA to be old_tableA and created a new table ...
1
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2answers
158 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
101 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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0answers
74 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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27 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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4answers
417 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 - ...
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1answer
57 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 ...
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1answer
189 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 ...