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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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
votes
1answer
279 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 ...
0
votes
1answer
110 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 ...
0
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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
90 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 ...
3
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1answer
109 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 ...
0
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0answers
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 ...
1
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0answers
47 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 ...
1
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1answer
42 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 ...
0
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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
86 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, ...
1
vote
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 ...
1
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0answers
84 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 ...
3
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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
votes
2answers
198 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
116 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
votes
1answer
105 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),...
3
votes
0answers
88 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....
0
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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'...
2
votes
3answers
392 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 ...
7
votes
6answers
932 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
128 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
votes
1answer
119 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
vote
2answers
161 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 ...
1
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0answers
105 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 ...
0
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0answers
98 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 ...
0
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0answers
29 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 ...
4
votes
4answers
422 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 - ...
0
votes
1answer
64 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
vote
1answer
230 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
votes
1answer
162 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 ...
0
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0answers
68 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 ...
5
votes
3answers
492 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 ...
1
vote
1answer
58 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": { "OrderId":...
1
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0answers
25 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 i5-...
1
vote
1answer
31 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
votes
0answers
25 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 /usr/sbin/mysqld(my_print_stacktrace+0x35)...
0
votes
1answer
88 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 ...
0
votes
2answers
64 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 ...
21
votes
2answers
925 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, ...
0
votes
1answer
33 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 ...
1
vote
0answers
45 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 ...
0
votes
0answers
78 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 that(...
1
vote
1answer
166 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 ...
-2
votes
1answer
24 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? ...
0
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0answers
95 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
vote
1answer
66 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
68 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 ...
0
votes
0answers
39 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 ...