Use this tag for questions about improving the performance and/or efficiency of database queries.

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1
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1answer
343 views

set global variable parameter?

My prod_server version is 5.1.47 and want to set the slow query log dynamically for certain period of time. I refered one site(http://toastergremlin.com/?p=276) there is mentioned below 5.1.6 we need ...
4
votes
1answer
433 views

Subselect of MAX(Version) takes many minutes, though there are only ~20K records

I have a pretty complicated data model. I can't understand most SQL examples without an explanation of what's being modeled, so I'll try to explain. Mainlines -> Releases -> Overlays -> Calibrations &...
1
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2answers
226 views

Why would a query work slower when a where clause is added?

I've got two databases and both have got the same view over the same table which has the same indexes. The view selects the top location for a given IMEI from a locations table. CREATE VIEW [dbo].[...
0
votes
1answer
51 views

Query results that not are in previous query result

I want to retrieve from my table the id_product of the products which haven't got some attribute and it's value is not the ones i want For example i want the id_product of the products in which ...
1
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0answers
261 views

Simple avg query on large table much slower in PostgreSQL than SQL Server

I have a database with three tables items, parameters and measurements in both servers and want to query the measuerment table. But the query is much slower in PostgeSQL (9.4) vs SQL Server (2012). ...
3
votes
2answers
56 views

Is it a better idea (performance is key) to store in a normalized table and retrieve by JOIN or in a single nvarchar column and retrieve using LIKE?

NOTE: The application is not really about websites or keywords, I am using that here only to provide reference points for discussion. I have a data set that is really just a string of words. Think of ...
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0answers
33 views

Sampling and matching samples with spatial conditions

The Problem I have two tables with start points of a route and possible end points of a route which need to be matched against each other. I also have a given distribution for the distance between ...
3
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2answers
1k views

How to speed up select distinct?

I have a simple select distinct on some time series data: SELECT DISTINCT user_id FROM events WHERE project_id = 6 AND time > '2015-01-11 8:00:00' AND time < '2015-02-10 8:00:00'; And it ...
0
votes
1answer
49 views

Mysql JOIN with 25million rows

Recently I got stucked with a table where its grown to +25million and I have got a query that's doing a JOIN on it. The query take 2.5hours to execute even though I got Good 96GB RAM and RAID10 with ...
0
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1answer
53 views

MySQL - How can I improve this query? EXPLAIN attached

I have a query that I feel should go much faster then it does. Right now it'll execute around 1,5xx secs each time. I don't have any advanced knowledge of looking at the EXPLAIN and draw conclusions. ...
2
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0answers
31 views

Query optimization - contact should be extracted at most once for a particular customer

I have created a database for a telemarketing company Scenario is, the telemarketing company is selling contacts to the customers. Customers log on to the website and search for the contacts for ...
1
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1answer
162 views

intermittent performance issue - query with multiple CTE and trashed execution plan

I'm trying to optimize a SQL query that shows variable performance (less than 2 to more than 15s). Overview This is a ColdFusion website, with a SQL Server 2008 R2 backend The query is part of the ...
2
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1answer
160 views

Mysql Partitions with Partition limit

I have a partition table on basis of Primary key having 1.5 Billion rows in it. But when i check ibd files only 80 ibd show in GB's whereas 120ibd shows 1MB file. I would like to know how does the ...
1
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2answers
205 views

1 hour query, is there another way to do this?

I saw a couple questions similar to this but none could answer my question, really. I have two tables, and I am trying to find those rows where a match is found. user has about 350,000 entries and ...
3
votes
2answers
82 views

Slow queries on production Server

I am a developer who has been asked to look at a database slowness issue. I have had a look at the waits on the server and retrieved the following using a query from Red Gate's wait stats white paper. ...
1
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1answer
2k views

Optimizing Amazon RDS - MySQLTuner Recommendations / Feedback & Suggestions

I'm currently trying to optimize a database I've inherited for speed. The server is an Amazon RDS db.m3.large instance: 2 VCPUs 7.5 GB Memory 500 GB HDD My current strategy is to do the following:...
1
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0answers
158 views

How to optimize inefficient query in PostGIS

I'm doing some queries on a PostGIS, and some of them take a really long time ( > 60 secs). My queries are like this, except querying different tables (like osm_placesbelow). This query takes about ...
2
votes
1answer
5k views

#2014 - Commands out of sync. you can't run this command now. Query was working before. But now it is not working

My table structure is ... There is Counter which has many Box in it. Box has a one BoxType. and Collection stores Box datewise revenue and data. I need data of particular 1 COUNTER (Data of All the ...
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0answers
43 views

How to query against legacy data that needs to be cleaned up?

I have an existing SQL Server DB with 3 tables (note: this is a made up example, but modelled after a real problem). Artists : contains music artists MusicRecords : contains information on music ...
1
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0answers
56 views

Is it bad practice to launch more than 100 sql statements at once?

I have PHP code that is meant to updating the billing status of someone. I only want it to update if the bill has been successfully created and therefore I think a possible solution would be to ...
2
votes
1answer
616 views

SQL Server 2012 stored procedure runs very slow sometimes

I have a stored procedure with a single large query which takes an ID as a parameter and returns some counts. It has quite a few inner joins and left outer joins but they are all on indexes. The ...
0
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0answers
48 views

Can an index be added to a PRIMARY with a null key?

I have a query that takes a long time to return, roughly 12-15 seconds, which I'd like to optimize. The query below is the result of running the original query with SHOW WARNINGS. If I run EXPLAIN ...
0
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0answers
454 views

Multiple user roles with different attributes

I need to design a database that has multiple users, with multiple roles. For instance, a user can be an admin, company, employee, or customer. Each user can have any number of these roles. Right now ...
0
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0answers
108 views

Multiple subqueries performance issue

I have a query that collects customer data. I select a lot of correlated data from different tables. I want to have only ONE result row for each customer. The query looks like that: SELECT c.Id ,c....
0
votes
1answer
378 views

Why does MariaDB 10.1.2 blow away MySQL 5.6.22 in sysbench?

Problem Maria DB is doing roughly twice the number of transactions that mysql is using standard oltp benchmark. The VM and db's are both fresh installs from vendor apt repos with default configs. ...
4
votes
1answer
612 views

Unused index in range of dates query

I have a query that is not using existing indices and I do not understand why. The table: mustang=# \d+ bss.amplifier_saturation Table "bss....
1
vote
1answer
51 views

Can I use SPARSE somehow on a non-nullable bit column with mostly false values?

I have a table that stores the results of queries that are run at least once a day. There's a bit column that represents whether the row is from the most recent run of a particular query with a ...
4
votes
2answers
183 views

Take advantage of monotonic columns in PostreSQL

I have a PostgreSQL table with, among the other, two columns named col1 and col2, both of integer type (there are around 10M rows in the table). I want to perform SQL queries like: SELECT * FROM ...
3
votes
2answers
207 views

Updating large table worked before, now taking hours

BACKGROUND: I am using a non-production SQL Server to manipulate a large data set and run a few basic calculations. The original data file I have, which is about 30M rows, is missing records (not NULL;...
2
votes
1answer
1k views

Amazon Redshift - The difference between Query Slots, Concurrency and Queues?

We are building a business intelligence system, and we have a huge PostgreSQL Database (DB) where we make all the info processing, and a Redshift Data Warehouse (DWH) where we store the data and ...
1
vote
3answers
472 views

Slow query when adding additional where clause

Here's my setup (Postgres 9.3) Posts project_id Messages post_id kind updated_at I'm trying to get the most recently updated 100 messages that belong to posts (on a specific project) that are ...
0
votes
1answer
111 views

How bigger page size effect at performance?

I know in case of Cluster index bigger page size improve peformance for range and multipoint query. Does bigger page size can effect to degrade performance when we have non cluster index .Because ...
2
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0answers
203 views

Oracle instead of trigger update performance issue

I have a large table containing over 15million records with 4 columns that form a compound key. Because we use a development environment that doesn't support compound keys I was required to create a ...
2
votes
1answer
146 views

Retrieving latest record using DISTINCT ON is slow [duplicate]

Using Postgres 9.4. I have a table cartests with 5.5M rows. Each row is a car test: \d log.cartests; Table "log.cartests" Column | Type | Modifiers ------------...
4
votes
1answer
313 views

How to optimize: having COUNT(*)>1

Without considering the indexes, Is there a way to re-write this query and get the same result quicker? select fo.OrderNo, fo.OrderItemSeqNo, COUNT(*) from Facts.FactBackOrder fo group by fo.OrderNo, ...
0
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0answers
46 views

Propper way to handle NULL (empty) values for User Definde Table Types passed as params to sproc

My stored procedures accepts table value parameters for querying data. Usually those are custom User Defined Table Types for where clause. Business logic of stored procedures push me to these @tables ...
2
votes
1answer
975 views

Performance of query with complex where clause on 10M rows

We have a query that destroys our production server when run. It is part of a reporting functionality and the bad part looks as follows: SELECT DISTINCT mt.ID AS ID FROM [dbo].[...
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0answers
50 views

Is there any way to improve this code?

SELECT tblstud.studid, tblsched.ip FROM tblstud LEFT JOIN tblstudsched ON (tblstud.studid=tblstudsched.studid) LEFT JOIN tblsched ON (tblstudsched.schedid=tblsched.schedid) ...
5
votes
1answer
2k views

Scaling PostgreSQL TRIGGER(s)

How Postgres triggers mechanism scales ? We have a large PostgreSQL installation and we are trying to implement an event based system using log tables and TRIGGER(s). Basically we would like to ...
1
vote
2answers
66 views

Get the pais_id not associated to fabricante_distribuidor_id and producto_solicitud_id, the opposite from SELECT query

I have this query for get all the pais_id given a fabricante_distribuidor_id and producto_solicitud_id, the query works fine. SELECT DISTINCT nom.pais_id FROM negocio.fabricante_producto_solicitud ...
0
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0answers
20 views

Usage of temporary tables in my tempdb database on sql server 2005 [duplicate]

I am trying to resolve the disk space issue on one of my drives where tempdb residing occupies more than 100 GB: Stats shown below I read some similar post on the same and i found few queries using ...
0
votes
1answer
49 views

optimizing a select query of 1.5 million entry

I have the following query: SELECT s0_.id, s0_.lowresimageurl FROM app_instagram_shop_picture s0_ FORCE INDEX ( idx_deleted_shopId ) LEFT JOIN app_instagram_shop s1_ ON s0_.shop_id = s1_.id AND ( s1_....
8
votes
2answers
578 views

Simple DELETE, but complicated execution plan

When I run this delete: DELETE FROM ETLHeaders WHERE ETLHeaderID < 32465870 ...it deletes 39,157 rows. It should be simple because it is deleting on ETLHeaderID which is the clustered index and ...
1
vote
0answers
64 views

Can MySQL Index Merge an Composite index with a single column index?

I am tuning a query and currently have an index as following : Index 1 : (col1, col2) An example query would be : SELECT * FROM t1 WHERE col1 = '1' AND col3 = '2'; I have created an index on ...
0
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0answers
218 views

Slow Query Performance - Can't Debug

I have a MySQL query that I am trying to debug the performance issue but cannot. I know that the majority of the query is reading/processing rows (Sending Data state). However, in the explain output, ...
1
vote
1answer
162 views

Optimizing intersect query in MySQL

I'm facing a performances problem in our MariaDB server. We have a table linking users to pages, a user belongs to 1+ pages. I have a page that have users and I want to get the 10 best pages based ...
1
vote
1answer
104 views

Best approach to get last value inserted

I have several devices that report via Edge network their position (and more data) to a UDP server which directly inserts this data in a SQL 2008 r2. I want to know which is the best approach to ...
2
votes
1answer
113 views

Indexed View - how to verify if it is worthy?

I have the following indexed view: CREATE view VProcessStatus WITH SCHEMABINDING AS select processstatus, StatusCount = COUNT_BIG(*) FROM DBO.tbltaxtransaction GROUP BY ...
1
vote
1answer
68 views

Create a log file for check which time import has been done and to split the import files

How to create a log table for when does the last import has been done and also for Query for split the records in to 1000 while importing. to avoid the bulk insert For example : If the data ...
1
vote
1answer
136 views

What are the side-effects of disabling nested loops in postgres?

A query of multiple joins spends a lot of time on nested loops. I disabled the nested loops and the query ran much faster. However, I have been told that nested loops might give me wrong results by ...