A class of issues where a database executes a query inefficiently due to the optimiser selecting an innapropriate query plan.

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92 views

A single, simple update takes 10+ seconds

We are running MySQL 5.1.71-log and have a table with 2.7 million rows. Simple updates to it are regularly taking more than 10 seconds to execute. The table structure is: CREATE TABLE `person` ( ...
2
votes
1answer
603 views

How to get query runtime in PL/pgSQL to be as fast as console query runtime?

Basically I want to assign the result of a query to a custom type attribute. However I noticed that querying directly from the PostgreSQL console was about 0.071 ms and inside the function was 0.400 ...
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1answer
122 views

MySql: Slow join and group by on indexed columns

The following query takes 15-20s to run SELECT "Trade_US"."ID" AS "Trade_US.ID", "Server_US"."Name" AS "Server_US.Name", "Trade_US"."TradeTypeID" AS "Trade_US.TradeTypeID", "Users"."ID" AS ...
0
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1answer
106 views

Tuning Mysql and Monitoring

I would like to know if anybody can point me towards a tool/way for MySQL database tuning ... Actualy the tunning of my.cnf is like below My database is in MyISAM | Mysql 5.1.73 key_buffer = 500M ...
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vote
1answer
88 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 ...
0
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1answer
19 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 ...
1
vote
1answer
100 views

Mysql join table order by index

First Master Table CREATE TABLE `edipostingmaster` ( `ID` bigint(20) NOT NULL AUTO_INCREMENT, `applied` int(11) DEFAULT '0', `fileName` varchar(255) DEFAULT NULL, `checkNo` varchar(100) ...
-1
votes
2answers
138 views

View with left joins are very slow

I have a view based on join of 3 tables and and query on view is taking 10 mins to fetch the results. Can anybody help me in reducing the time taken to fetch results? VIEW CREATE view ...
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1answer
137 views

How to optimize query

using SQLite3 and the following query, it seems like there should be a better performing way to write this query? Is there? Select Name, Sum(Case When Used Is ...
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1answer
3k views

Select from a list of values from JSON encoded data

I have saved the details of the product in JSON format. I am wondering how to select from a list of values from a "JSON_ENCODED DATA" For Example I want to select TV with screen_type as LED or LCD. ...
4
votes
1answer
282 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 ...
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2answers
144 views

Slow fulltext search due to wildly innacurate row estimates

Fulltext queries against this database (storing RT tickets) seem to be taking a very long time to execute. The attachments table (containing the fulltext data) is about 15GB. The database schema is ...
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2answers
80 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 ...
0
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1answer
33 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
vote
0answers
42 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). ...
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2answers
189 views

Database is slow once in a while

I am executing a web service for 100 times. The average response time of this service is 1.5 seconds. But when I look at the response time of each execution individually, there are a few executions ...
0
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2answers
197 views

How can I optimize this query and support multiple SKUs?

My current query only can select one SKU at a time. I can leave salesite_id constant. If there is a way to also have varying salesite_ids that would be good too, but not necessary. Also any ...
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0answers
87 views

How to calculate database query accurate responses? [closed]

I was given a set of data, 100000 rows of data queried using statistical interface for average value of an attribute. The response is determined using the random-sample query method, with subset of ...
2
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2answers
40 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 ...
2
votes
1answer
144 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
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0answers
19 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
votes
1answer
988 views

Optimizing large database query (25+ million rows, using max() and GROUP BY)

I'm using Postgres 9.3.5 and I have a large table in the database, currently it has over 25 million rows and it tends to get even larger rapidly. I'm trying to select specific rows (all unit_ids with ...
0
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1answer
97 views

Complicated data

I have a requirement i got from my father. He gave me a table and wanted me to digitalis it. So that he can the system can do all the dirty jobs for him ( that's why there are developers in the world, ...
3
votes
2answers
439 views

SQL server query is slow *without* including execution plan

I have just set up fresh installation of SQL Server 2012 on a new server and I'm experiencing very strange performance problems. Long story short, for some reason not including execution plan makes my ...
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1answer
63 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 ...
3
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2answers
378 views

Query planner thinks doing a sequential scan on a very large table is faster than using an index?

I've got a query that selects the most favorited photo for each of the last 12 editions for a particular domain (this is just a segment of a larger query, but the problem seems to stem from here): ...
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1answer
43 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 ...
2
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1answer
124 views

Minimizing Page Fetches

I have a complicated database structure and am trying to use it to retrieve Records based on multiple selection criteria from several tables. As a general rule, is it better to attempt to use ...
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0answers
195 views

How can I use mongoDB efficiently in this scenario?

I'm trying to build a system of documents that have hundreds of tags assigned to them, but each document-tag association has a certain condition it has to also meet so the document would be returned: ...
2
votes
1answer
58 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 ...
1
vote
1answer
66 views

optimizing query for slow queries

I have this query in my slowqueries table which essentially is taking about 5-8 seconds to complete the query time: SELECT s0_.id AS id0, s0_.updated AS updated1, s0_.created AS created2, ...
13
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1answer
6k views

SQL query for combinations without repetition

I need a query which can be used in (or as) a function and retrieves all combinations of n values. And I need all combinations of length k where k = 1..n. Extended sample input and result so input ...
0
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1answer
39 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. ...
0
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1answer
104 views

Rerunning query in the same connection takes significantly longer

I am having a weird issue when a running a query that joins some semi-large tables (one table is about 2 million rows and the other about 21 million) together. What happens is the query does not run ...
0
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0answers
17 views

Inner join slow with distinct

I know my query below is just horrible and it takes 2 min to get 10 records (listing table has over 1M records though) but I am not sure whats the better way to write this I simply just wanna get all ...
2
votes
0answers
18 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 ...
0
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1answer
27 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 ...
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2answers
85 views

Simple query is slow on 4M-rows table

I have in production a MySQL table pageviews with 4M rows that records page views of users on posts. I need to know which posts a specific user have read, but this request takes up to 15 seconds to ...
0
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1answer
91 views

MySQL: Optimize query with a range and distinct count

I have a query on a large table with millions of rows that looks like this: SELECT COUNT( DISTINCT clicks.tx_id ) AS unique_clicks_count , clicks.offer_id FROM clicks WHERE ...
1
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1answer
3k views

statistics State in MySQL Processlist

I have a busy MySQL Server having query SELECT sys_sess_state, index_state, timeout_lvl, last_queued_dt, last_polled_wait_dt, create_id, create_dt, modify_id, modify_dt FROM PQR_AM_SYSTEM_SESSION ...
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0answers
26 views

Postgres - Optimizing a View Query

I have a view which gets populated by approximately 150,000 records per day. The data from the view is consumed by another application. While reading the view, it takes almost 10 minutes, which is a ...
1
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1answer
28 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 ...
2
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1answer
83 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 ...
0
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1answer
995 views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
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vote
2answers
66 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 ...
0
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2answers
172 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
1
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1answer
65 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 ...
2
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2answers
607 views

Slow queries on billions-rows-table // index used

Since I'm a young developer and not really skilled in using databases (PostgreSQL 9.3) I ran into some problems with a project, where I really need help with. My project is about collecting data of ...
0
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2answers
2k views

Optimize IN clause in where query with order by - MySQL

I am trying to optimize a query that using IN clause in WHERE to avoid file sorting. To make it easy , I created the following sample which shows the problem. Here is my query: SELECT * FROM `test` ...
2
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2answers
58 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. ...