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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5
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245 views

Performance inner join vs left join involving parallelism

I have a query which takes about 8 hours to finish. Simplified, the query looks something like this: SELECT [Some attributes, inconsequential] FROM RBM.Financial_Events RFE INNER JOIN ...
5
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0answers
160 views

Measure SQL Azure Transaction Rate

We are on SQL Azure v12 Standard/S2 Service Tier and are not satisfied with the performance so I am trying to measure where the bottleneck is. I realize that we could be hitting the limits of the S2 ...
4
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0answers
118 views

How can we improve this PIVOT operation? ( SQL Server 2008 R2 )

We have this query, that runs in 1:10. We need to improve this. This is just a test query, but we will implement this upgrade on our real query. select top 100 * from ( select codCliente ...
4
votes
0answers
3k views

How to properly monitor the number of PostgreSQL database connections?

I tried to use a Nagios script for monitoring the number of database connections on a Postgres database and I reached this problem: these are counted as currently open-connections and measured every 5 ...
3
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0answers
48 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 ...
3
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0answers
52 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 ...
3
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0answers
84 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), ...
3
votes
0answers
595 views

Slow inserts/updates into partitioned table with lot of partitions

I'm designing the partitioning for our new database, but we are facing performance issues in inserting or updating the partitioned table. For simplicity suppose we have one table T, which have an ...
3
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0answers
49 views

Isolate database performance on an instance

I have SQL Server 2014 Standard Edition installed on a machine with two different users and two catalogs, each of them accessed by a different user (each user is strictly tied to his catalog). Is it ...
3
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0answers
348 views

Are there any known benchmarks/statistics on UnQLite?

I came across UnQLite the other day in Stack Overflow and it has me intrigued for some software I'm working on. However, very few tests have been published on how well it performs. There are plenty of ...
3
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366 views

Slow transactions, many locks

At high load conditions the server app stops responding to client because begin/commit statements are executing very slowly (some take 15 seconds). The queries are simple - insert, update two columns ...
3
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0answers
83 views

Can CTE sub-statements be prevented from executing at all?

Through this strategy, time consumed by queries for my application have dropped to extreme lows; however, some queries consume more milliseconds than necessary. The reason why is that upon ...
3
votes
0answers
152 views

Optimizing postgres row overlap constraints involving UUIDs and GIST

For various reasons all my tables have UUIDs as primary keys and I need to exclude duplicate rows where the combination of area_id, user_id, and finished_at <-> started_at window. The only way I ...
3
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0answers
81 views

Oracle - physical writes to an index

We have a large UPDATE (affects about 200K records) on a huge table (80M records). Due to a coding mistake, the UPDATE updates the same set of rows (200K) all over again with the exact same value. ...
3
votes
0answers
65 views

Sample a Mysql table to increase performance

we are storing all our clients traffic data in a MySQL 5.1.73 database (MyISAM) and then we use it to generate user and internal statistics/graphs, always searchinng for a client id and a date/hour. ...
3
votes
0answers
742 views

Do OR conditions in Oracle SQL queries spoil index use / cause full table scan?

I have a query on Oracle 11g of the following type, which results in a series of highly inefficient full table scans: select t.Id, t.ObjectId, t...[other Tasks columns] , od1...[ObjectData1 ...
3
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567 views

Poor performance in my pgpool cluster

I've configured a postgres cluster with pgpool2 using the following link. The replication seems to be ok, but I ran some benchmarks (pg_bench) and the performance is lower than a single node, for ...
3
votes
0answers
649 views

Fastest way to get the length of the intersection of two text arrays in PostgreSQL

This is what I am currently using: CREATE OR REPLACE FUNCTION array_intersect(a1 anyarray, a2 anyarray) RETURNS anyarray AS $$ select array ( select unnest($1) intersect select unnest($2) order by 1 ...
3
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0answers
2k views

Oracle high Paging Faults

What are the reasons that lead to terrible high Paging faults. The following is the topas information and background about the Environment. OS: AIX 6.1 Softwares: Oracle 11gR2 Paging Space:30720 ...
2
votes
0answers
45 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 ( ...
2
votes
0answers
25 views

Implications of many materialized views in Postgres?

I'm working on a system that includes a scheduling component, which has support for recurring events. After reading many, many posts on storing recurring events, it was suggested that they be ...
2
votes
0answers
63 views

Postgres: CREATE INDEX, but very slowly, to reduce performance hit on rest of database?

I have a large production PostgreSQL (9.1) database running on Ubuntu Linux. It is currently being queried and used. However there is another use I need later, and I will need to create a large ...
2
votes
0answers
49 views

Simple insert with Wait_Info = WRITELOG()

We have a query ( the same as some questions I made here ). a simple insert: INSERT INTO [My_Ttable]([IDChamada],[Evento], [Resposta],[IDTarifador],[ProximoEvento],[NomeDaMaquina],[DataMaquina]) ...
2
votes
0answers
61 views

Query that can benefit from index, cluster or hash-cluster

I'm trying to find a equi-join query that shows a decent performance bump when I use an index, cluster or hash-cluster structure on my data. I initially need to run the query on unstructured data ...
2
votes
0answers
95 views

Transaction log bloat when writing to table on replicated database with parameterized filter

We are observing abnormally large log writes whenever we update a table that is used for parameterized filter in a merge replication. There are a number of join filters as well. When executing a ...
2
votes
0answers
95 views

Performance Implications of Explicit Collation Conversions across Linked Servers

I locally host host databases from two vendors on two different SQL instances, but on the same network. These servers frequently communicate with each other (through joins and whatnot), so we have ...
2
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0answers
77 views

Is it possible to trace queries that never complete with SQL Server 2008 R2?

Running SQL Server 2008 R2. We have some queries that typically take less than one second to complete, but, occasionally, they are taking longer than 30 seconds which causes a client timeout. ...
2
votes
0answers
253 views

Case Statements, subqueries, and datediff

First time posting on this website so please let me know if you require any other information. This first section of code worked perfectly and resulted in correct information. [Field 1] = (CASE ...
2
votes
0answers
3k views

How to resolve RESOURCE_SEMAPHORE and RESOURCE_SEMAPHORE_QUERY_COMPILE wait types

We are trying to figure out root cause of slow running sql server queries hitting/fetching data from one of the database , size 300 GB, hosted on server with below configuration: Windows server ...
2
votes
0answers
83 views

SQL - Optimize table population with dynamic queries

I need to optimize the following pl/sql procedure. So, fundamentally my question is: There is a way you can do a bulk insert in a pl/sql that could be more efficient than loop through an associative ...
2
votes
0answers
304 views

Excessive CPU Usage caused by long running query?

We have been getting intermittent excess CPU usage at 100%. There is not a whole amount running on the system. We also get warning of Batch Requests/sec above threshold.: 1030, which would seem to ...
2
votes
0answers
210 views

Oracle: separate column histograms for partitions

I have a partitioned table like MY_TABLE(PART_KEY, DATE_KEY, ...) with a local partitioned index on (PART_KEY, DATE_KEY). When I collect stats on the table, I end up with a HEIGHT BALANCED histogram ...
2
votes
0answers
402 views

Any way to speed up my queries in MariaDB with tables less than a 4 GB in size?

I'm doing some text mining work and a bit frustrated that queries are taking 6 to 10 minutes to run. My workstation has a 3.5ghz Xeon, 32GB of RAM, and 2 SSD as RAID 0. Is it possible to do ...
2
votes
0answers
167 views

Find Most active databases that can be offloaded from a busy server

I am in the process of identifying the most active databases on the server and will be moving the databases off the current server to alleviate the load. The reason to do it is that our servers are ...
2
votes
0answers
172 views

Why does removing a RID by creating a clustered index lose parallelism and slow down execution by 2X

If I remove a RID lookup by replacing 2 non-clustered indices (non unique) with 2 identical clustered indicies (non-unique) where there weren't any before, why does this query slow down by a factor ...
2
votes
0answers
1k views

Mysql slow writes

i have a strange problem with mysql. My selects goes fast. My insert/create/delete/drop/update go very slow. I have done some tests on 2 machines. My old machine and my new machine. Old is worst ...
2
votes
0answers
82 views

Performance of database with transactional data

There are lots of row modifications (several thousands of rows per minute) in our PostgreSQL database that stores transactional data. We have a problem because PostgreSQL runs vacuuming process and ...
2
votes
0answers
675 views

How to calculate running total based on dynamic values?

I need to calculate the running total in which the target column is changing along with the time. Its something which aws does. Charging based for only what you use. So how do I aggregate sum of ...
2
votes
0answers
92 views

How can one improve the performance of a query that selects on a low cardinality column in MySQL?

I have a "State" column that has a low cardinality (three possible value), on which most of my queries perform an equality selection (WHERE col = 'blah') AFAIK you need something like a bitmap index ...
2
votes
0answers
864 views

MySQL: Improve performance for one row insert into table with unique constraint

I have a table with ~ 40 mil records, with a unique index on the url collumn, of type varchar(255). Now the insert speed is about 30/s, is this expected? how could I improve it? I can't use bulk ...
2
votes
0answers
141 views

How To Analyse Index Scans

I am using merge replication with SQL Server 2012. During a sync using a merge agent there are a large number of index scans. I can see this by running a profile capturing SCAN:Started and ...
1
vote
0answers
23 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 ...
1
vote
0answers
38 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 ...
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vote
0answers
20 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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vote
0answers
49 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 ...
1
vote
0answers
35 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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vote
0answers
28 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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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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vote
0answers
52 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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vote
0answers
76 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 ...