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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4
votes
1answer
105 views

Slow Delete's of LOB data in SQL Server

I have a tables for logging, and a stored procedure to purge old data that has very slow DELETE performance, beyond what makes sense to me. I am looking for how to modify the tables or DELETE ...
0
votes
1answer
59 views

Maximum number of TEXT/BLOB columns per table/performance of table with many of them?

I've created a system that generically imports CSVs into a database table with metadata columns for keeping track of when a CSV record has been changed, and it allows filtering on CSV columns instead ...
6
votes
2answers
292 views

Are cursors/While loops the only way to make administrative changes to multiple databases?

I specifically want a programmable way to change the recovery model of all the databases on a server, and i know this solution can be applied to all 'Alter Database' commands. While I know SMO in ...
0
votes
1answer
58 views

Same query same data different server different query plan

I have a query that hits a view, which references other views etc...several levels down. The query plan is a bit complex. I run the query on 2 different servers. On both servers, the number of rows ...
3
votes
1answer
69 views

Amazing improvement of script execution speed when split - not understood

I have an ETL job that merges data into about 20 columns of a fact table, all integer non-null (default 0) columns. There are 8 merge statements to completely update all the columns and they involve ...
3
votes
1answer
71 views

Execution time with warm up cache

I have a query that takes around 1 second on first execution and 15-50 ms after running the same query again. The only difference between EXPLAIN outputs is that the second execution contains a lot of ...
1
vote
1answer
44 views

SPID Change for a process?

On SQL Server 2012 can a process SPID change mid-operation? We have a very unique query that we've been monitoring (production, but controlled testing) and have seen it at different intervals with ...
6
votes
2answers
175 views

Does table size matter?

I have a table like this (with more columns though): CREATE TABLE [dbo].[MyTable]( [SnapKey] [int] NOT NULL, [SnapDt] [smalldatetime] NOT NULL, [Company] [varchar](4) NOT NULL, [...
14
votes
2answers
376 views

LOB_DATA, slow table scans, and some I/O questions

I have a rather big table with one of the columns being an XML data with an average size of XML entry being ~15 kilobytes. All other columns are regular ints, bigints, GUIDs etc. To have some concrete ...
2
votes
2answers
73 views

Filtering UNION ALL result is much slower than filtering each subquery

(edit: see end for a simpler example) I'm searching in a table named "cases" (135k rows, 29 columns). Some of the rows in this table have a type of parent-child relationship (of different types), ...
1
vote
0answers
29 views

problem with column oriented dbms features

I am currently looking for a free(or at least low cost) column oriented DBMS with really good compression abilities (at least 10:1 ratio) and fast response time. Having evaluated multiple open source ...
0
votes
0answers
52 views

Sql Server Stored Procedure calling table-valued function - Performance

I'm using Sql Server 2012 and I have a stored procedure that does about 15 left joins and one of those joins is a CROSS APPLY to a table-valued function. The first 14 left joins are not gonna restrict ...
0
votes
2answers
25 views

Good reason to convert LONGTEXT column to smaller width if field is smaller?

We have a database that uses a LONGTEXT type for a column that does not need that much space. The maximum row size currently has about 6500 characters and that's with a few million inserts so it's ...
3
votes
1answer
78 views

Finding hash match aggregate

After reading following blogs, I understand that hash match aggregate causes blocking. Using appropriate indexes it can be made as stream aggregate. Blocking/non-blocking aggregate operators The ...
3
votes
1answer
95 views

Improving mongodb read throughput for tiny database

I am given to understand that MongoDB will essentially perform like it is pulling records from memory if the working set is small. I wrote a simple MongoDB test program that inserts just one record ...
2
votes
0answers
47 views

Clustered index on a fact table

I'm trying to work out what field(s) to use for the clustered index of my fact tables (which all have a similar structure). I'll use FactSales as an example: CREATE TABLE dbo.FactSales ( ...
1
vote
2answers
34 views

Mysql Query Take Longer To Prcoess On My Dedicated Server Than My Local Server

One of my MySQL queries takes a very long time to process on my live server compared with my development server. My live server (Windows dedicated server) is more powerful than my local (development) ...
2
votes
1answer
50 views

Possible causes that a MySQL/MariaDB query is slow under some table conditions

I am having a strange issue with a slow query under certain conditions: I have made a few tests and was able to isolate the issue to one single table called products_description (all the tables are ...
1
vote
2answers
50 views

Database logging optimization and maintenance in SQL Server

One of the Web applications I am working on, uses NLog to log debug and error context information in the database. Basically, it performs a moderate number of inserts (I appreciate some tens of ...
1
vote
0answers
47 views

SQL Server 2008R2 - BAK file backup performance issue

Just note I'm not a DBA or anything close to that. Problem: We are using SQL Server 2008 R2. We have 32 databases and backup to local disk (3PAR) using SQL Server maintenance plan. Normally it ...
0
votes
1answer
39 views

Storing mail in database, data type

I've found pretty poor informations about mail databases. My need is to archive mail messages downloaded from a normal pop3 or imap account: I am an ordinary user and I do not own the server, but ...
0
votes
0answers
44 views

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 ...
3
votes
1answer
37 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 ...
0
votes
0answers
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". ...
0
votes
0answers
56 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 ...
2
votes
2answers
63 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 ...
0
votes
1answer
28 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 ...
1
vote
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 ...
0
votes
0answers
21 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 ...
2
votes
2answers
75 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 --...
1
vote
0answers
59 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?
0
votes
1answer
66 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 ...
2
votes
2answers
61 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 ...
1
vote
0answers
57 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 ...
0
votes
1answer
28 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 ...
0
votes
1answer
63 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 ...
0
votes
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 ...
0
votes
1answer
48 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 ...
1
vote
1answer
67 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 ...
6
votes
1answer
151 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 ...
0
votes
1answer
34 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 ...
3
votes
3answers
67 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 ...
1
vote
2answers
132 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 ...
1
vote
0answers
40 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). ...
1
vote
0answers
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 ...
5
votes
2answers
474 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 ...
5
votes
1answer
195 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 ...
2
votes
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)...
1
vote
2answers
129 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 ...
0
votes
0answers
19 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 ...