Improving the performance characteristics of a database application or system.

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134 views

Mongodb Huge Number of Open Connections and Write Locks

We are seeing around 800 open connections to our Mongodb. To clarify our issue: We have 5 different clients who write the data into Mongodb. Each of these clients - write four different type of ...
3
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3answers
193 views

Simple yet problematic update query

I have a rather simple update/query, that has been causing me a lot of grief over the years. in simplest form it is : update VillageSemaphore set TimeStamp = getdate() where VillageID in ...
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31 views

Minimum Oracle table size making IOT advisable?

I have inherited an IOT that doesn't seem to merit it because: only 25k rows fairly pure join table, non-index fields rarely queried total index width only ~125 bytes total row width only ~160 bytes ...
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0answers
121 views

Why my mariadb slow when I select all from empty table?

I try to find why my database slow when I select all table . That's empty table... MariaDB [kohadata]> select count(*) from biblio; +----------+ | count(*) | +----------+ | 0 | +----------+ ...
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2answers
61 views

Can moving tables to another MySQL database help performance?

I want to know if I using different databases can help performance. I have one big table support_chat with more than 5 million rows. I need to scan this all the time (3s with ajax) to check new ...
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0answers
53 views

Mariadb improve performance while import dumpfile

I have a dumpfile with millions data inside. I want to decrease time because I waited too long. I imported 10 million data (3 GB) and I waited 1:30 hours. I will import nearly 100 million data (30 GB) ...
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1answer
587 views

Do I have a memory issue?

I ran sp_Blitz that pointed me to a memory issue saying: Memory Dangerously Low The server has 32755 megabytes of physical memory, but only 235 megabytes are available. As the server runs ...
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1answer
57 views

Sql Server 2012 Failover Replica in Synchronous Mode between Primary-Secondary on VPN is very slow

I have installed SQL Server 2012 Clustered HA with Replica in Sync mode between two nodes connected by an high-speed VPN. The DB is encrypted. Everything works fine, but to do the replication, the HA ...
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2answers
302 views

Why do SQL Server row estimates change when I add a join hint?

I have a query that joins a few tables and performs pretty badly - row estimates are way (a 1000 times) off and Nested Loops join is chosen, resulting in multiple table scans. The shape of the query ...
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59 views

SQL Server File Latency

I've a Database which is in SQL Server 2012. For the last couple of weeks it's very slow and some times not responding to the queries. So I checked the read/write latency and the result is - Read ...
2
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1answer
98 views

How to tune the query on all_constraints in Oracle 12c?

How to tune the following query, as it's taking around 8 seconds: select constraint_name,table_name from all_constraints where r_constraint_name in ...
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0answers
71 views

PAGEIOLATCH_SH and WRITELOG waits

We have a slow overnight process which I was asked to look at with the top waits being PAGEIOLATCH_SH and WRITELOG I have been collecting information from sys.dm_io_virtual_file_stats and can see ...
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1answer
231 views

Does RSS Profile have an effect on SQL Server with NUMA setup?

I'm curious whether the RSS Profile which is default NUMAStatic on Windows 2012 R2 could/should be changed for SQL Server with a NUMA setup. Has anyone done performance benchmarks on high load SQL ...
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1answer
120 views

Identifying root cause of high cpu load

I need to research what caused a high load in our Oracle database some days ago. I wish to see a list of of high-load SQL statements. We don't use any Oracle tools like ADDM or AWR. I tried to ...
2
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1answer
57 views

Associate SQL Server Queries with Databases

Is there a way via T-SQL and DMVs to show which database a query was run against? The goal is to look at CPU and I/O by query by database so I can redistribute the databases as I reconfigure the ...
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76 views

Update queries randomly slow on INNODB Mysql

I have been struggling with a slow update query. Have already tried using indexes and other query optimization techniques. I have been using MYSQL database with INNODB engine. The issue is that, ...
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0answers
21 views

Several Data Importation Illogical Latency in MySQL [closed]

I am used to importing a 4GB of data from an .sql file towards a testing server (hardware). I tweaked the database to speed up inserts, and, so far, the script takes 6 hours, more or less. We were ...
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3answers
53 views

Speeding Up MySQL Full Text Search

I am doing a complex full text search on a table with 130k+ records. It takes .5 seconds to complete. I was hoping it would be a bit faster. Is there anything I can do to make it faster? Below is ...
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0answers
41 views

Howto measure improvement after create and move new filegroups in SQL Server [closed]

How can one measure the (hopefully) positive effect of moving couples of indexes to a different filegroup, so to say seperate them from the primary data filegroup, and move this filegroup to another ...
3
votes
1answer
189 views

PostgreSQL doesn't use all the RAM it could

I'm having performance issues with my PostgreSQL 9.4.1 server. I have tuned the server using the usual best practices (pgtune + google). Here's the relevant config: # <snip> the default config ...
0
votes
1answer
109 views

Oracle 11g PGA advice view is empty when it shouldn't

I have the following situation in an Oracle 11g server (it's part of a RAC). PGA_AGGREGATE_TARGET is set, STATISTICS_LEVEL is TYPICAL, and yet V$PGA_TARGET_ADVICE shows up empty. Why does this happen? ...
7
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2answers
3k views

Latin1_General_BIN performance impact when changing the database default collation

I have set the database collation to Latin1_General_BIN, to make string comparisons case-sensitive. Will this have an impact on performance? Will it have any impact on DML or DDL operations in the ...
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0answers
222 views

DB CPU parameter in AWR - Oracle

What is the significance of DB CPU paramater in Automatic Workload Repository? Say in my case it's always above 100. Does it have benchmark metric as such to say that so and so number is the right ...
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0answers
33 views

Why do Statistic recommendations disappear from DB Tuning Advisor after implementing recommended indexes?

Why is it, when analyzing a query through Database Engine Tuning Advisor, statistic recommendations disappear after some or all of the suggested indexes are implemented? For example, Query X suggests ...
2
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1answer
753 views

Can I exchange partition between two table with partition with same name?

I am trying to restore one partition from a backup table. Both tables have partitions with the same name. My goal is to grab the data from the backup table partition x and put it in original table ...
1
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1answer
24 views

Access to Server and Real Data for Performance Tuning [closed]

I'm newbie in performance tuning (PT) in SQL server and I have read some documents about how to do it. It is based on theory from the articles or books. The next step to is to learn about it by ...
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4answers
1k views

Should the index on an identity column be nonclustered?

For a table with identity column, should a clustered or non-clustered PK/unique index be created for the identity column? The reason is other indexes will be created for queries. A query which uses a ...
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2answers
559 views

How to tune a stored procedure that is fast on test data but slow in production

If you have a SQL Server 2012 database with test data in development and preproduction phase and the real from the company's server take place only in the production phase. In other words, the real ...
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1answer
57 views

Tuning MySQL query from explain

I am working on a search query in MySQL. I am getting this from explain: Original screenshot These are my indexes: Table definition: Original screenshot Query: SELECT `t`.`id` AS ...
3
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1answer
308 views

Postgres 4x Slower Than It Was

Our Postgres performance has gone down to 1/4 of what it was, and we can't figure out why. We have two machines with identical hardware (let's call them A and B): Intel(R) Xeon(R) CPU E5-4640 0 @ ...
2
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1answer
186 views

Dropped Index during Database Engine Tuning Advisor

I was analyzing a query using "Database Engine Tuning Advisor". During this time the database started to get blocking, long running queries and ended by restarted the instance. When I checked after ...
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2answers
59 views

Finding the longest entries for a given column (nvarchar(100))

I am trying to find the biggest / longest entries of a column which is of type nvarchar(100). I need to understand if I can maybe restrict that column to be only nvarchar(20) or something. Is there a ...
3
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1answer
150 views

MySQL (MariaDB - 10.0.16-MariaDB-1 (Debian) strange performance issues

I am running version 10.0.16-MariaDB-1 (Debian GNU/Linux 8.1 (jessie)) on Dual Xeon CPU, total 32 cores with 128 GB of RAM. This is a dedicated DB server and has been recently migrated over from ...
2
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1answer
17 views

Is Oracle 10g smart enough to work on a WHERE clause identically as the equivalent INNER JOIN?

Way back when Michael Jackson was still alive, I made this question: http://stackoverflow.com/questions/1018822/inner-join-on-vs-where-clause And now I'm performance-auditing a system in which the ...
2
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0answers
70 views

MySQL memory is keep on increasing , any reason?

On one of our production host MySQL memory is keep on increasing day-by-day. I tried reboot of MySQL instance but still no avail. System has 16Gb of RAM. TOP output top - 13:05:13 up 35 days, ...
0
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1answer
66 views

NC Index not being used [closed]

I have a table (9mm records) with a field called filename nvarchar(max)(I didn't decide on this datatype and can't change it). I'm wanting to count how many records meet the following criteria: ...
4
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1answer
52 views

How to increase performance in Cross Database operations?

We currently have a SQL Server 2008R2 being accessed by a legacy ASP application. Among different processes, one of them essentially SELECTs data from one database and INSERTs (or UPDATEs) them into ...
2
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1answer
47 views

Accurate PG database size for comparing representations

I have a Java/JDBC program that takes a sample file and imports the data into the database, shredding it across multiple relations. The program does this multiple times for several different ...
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0answers
91 views

PostgreSQL query taking a long time

I have a query that is taking hours to run. There is a large table to parse, is there any way to optimise this? with VehData as ( SELECT * from dblink('host=databasesrv port=1234 ...
3
votes
2answers
348 views

Setting shared_buffers in postgresql.conf does not seem to take effect

We're on CentOS release 6.6, PostgreSQL version 8.4.20. (Yes, this is not bleeding edge.) In postgresql.conf, we have: shared_buffers = 4096MB kernel shm values are set nice and high: [root@green ...
0
votes
1answer
42 views

Feasibility of Automated and Continuous Performance Tuning in the future [closed]

First a quick background: I'm a software developer, not a DBA and have been developing for more than 10 years. Recently I had to optimize a stored procedure and had to run execution plans, ...
6
votes
1answer
163 views

Disk I/O and PAGEIOLATCH_XX

We have been having CPU issues with one of our servers lately and while we have been looking into this we have also noticed queries running slowly with waits of PAGEIOLATCH_XX. In particular, a ...
1
vote
1answer
665 views

Different execution plans during INSERT at @table variable and #temporary table

I faced with strange situation: inserting of ~800 000 rows into table variable is much more faster than inserting (with the same select) into temporary table. INSERT is under stored procedure. SELECT ...
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0answers
222 views

How to speed up for huge tables in SQL select query?

I have the following huge tables. Table_1 with 500000 (0.5m) rows Table_8 with 20000000 (20m) rows Table_13 with 4000000 (4m) rows Table_6 with 500000 (0.5m) rows Table_15 with 200000 (0.2m) rows ...
4
votes
3answers
393 views

Speed up creation of Postgres partial index

I am trying to create partial indexes for a large (1.2TB), static table in Postgres 9.4. My data is completely static, so I am able to insert all data, then create all indexes. In this 1.2TB table, ...
1
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1answer
122 views

How to speed up query containing concat() in WHERE clause?

In my company we use a commercial software running with mysql 5.5 (MyISAM) that often executes a query of this form: SELECT table1.attrib1 FROM table2, table1 WHERE table2.status = 'Active' ...
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155 views

MySql Innodb Database Slow INSERT Query to Remote Server

I have searched thoroughly on how to improve general performance of my database which is hosted on Hostgator. I have mostly come across performance tuning strategies which are catered to only local or ...
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0answers
51 views

Trigger copies history table: Will removing index lock options speed up the process?

I have a trigger applied to a table to write inserts and updates to a history table. That history table can grow pretty fast, and we want to see, if we can speed up insert operation a bit. The values ...
2
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1answer
139 views

Postgresql performance issues when issuing many small inserts and updates one at a time

I have a production web server with postgresql database. My server gets data from another server every hour on the hour. The other server wakes up and sends many requests to my server, each result in ...
0
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1answer
240 views

Scale MySQL trigger for thousands of inserts per seconds

We are using MYSQL database for an Analytics app. I have two table token and token-big (for overview of actual data) both have id(int) unix_starttime(int) unix_endtime(int) details(varchar 256) A row ...