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

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5
votes
1answer
768 views

SQL Server, TOP versus ROW_NUMBER

I'm learning about Execution plans and am trying out different queries and comparing their performance and stumbled upon this: SELECT StatisticID FROM ( SELECT StatisticID, ROW_NUMBER() OVER ...
0
votes
1answer
108 views

What is the best query to get the latest row version based on time?

I'm wondering what can be the most efficient query to get the latest rows from the following table. CREATE TABLE AGE_DATA ( INSERTED_DAY TIMESTAMP(6), HOSTNAME VARCHAR2(255 CHAR), CONCEPT ...
1
vote
3answers
77 views

Special function slow in where but not in select

I have kind of a special problem using a levenshtein algorithm in MySql. But I don't think that it's special for levenshtein. This query: SELECT *,levenshtein(word,'Facbook') FROM Words WHERE ...
0
votes
0answers
61 views

Auto update stats turned off for a user database on SQL Server

While trying to improve the performance of few queries, we found via execution plan that there were lot of index / clustered index seeks. Therefore: First thing we did, was to check our Re-indexing ...
0
votes
1answer
100 views

How to speed up mysql query against a 204 million record table

For some reason my server has been finicky lately and for the life of me I can't figure out why. I monitor the memory usage by running shell# watch -n 5 free -m without running any activities ...
3
votes
2answers
458 views

Efficently Remove 90% of a table's data

I am working on a process to remove 90% of a table's data because only 10% is needed for testing. The best way I have found includes storing 10% of the table's rows into a temporary table. Current ...
1
vote
0answers
46 views

Poor performance filtering mysql spatial join

First of all, sorry for the crossposting. I ask this question in stackoverflow and they sent me here I have a mysql table with spatial references (GEOGRAPHIC_FILTER), like cities, countries, natural ...
1
vote
0answers
55 views

MDX query is SLOWER with warm cache

I have a MDX query that executes faster on cold cache than warm cache. If I ran the same MDX query after restarting SSAS it takes 14 seconds. All subsequent runs of the same statement then take 50 ...
0
votes
0answers
54 views

SQL query running slow compared to its earlier execution time

One of our application using an SQL query is reported running slow. Current execution time:- 15 minutes and so Earlier execution time:- 30 seconds. SQL-Sentry Plan for the slow query I've ...
2
votes
1answer
39 views

Why can't I view the plan for view creation…?

mysql> EXPLAIN EXTENDED create algorithm =temptable view fisgen_temptable(inter,phone) as select intercom1,phone from fisgen where fid='f105'; I am getting an error like this: ERROR ...
1
vote
1answer
66 views

How to optimize a table/db with 200 insert/sec

I'm facing a very hard problem. I have a mysql DB (MyISAM) with a main table (user) where I write a row for every new user (around 10 fields). Every INSERT triggers around 10 new INSERT in 10 ...
5
votes
2answers
136 views

Sporadic execution time causing timeouts [closed]

We have a table with 100 million records holding 24 hour worth of data of our clients' customers actions (actions which are performed on 3rd party sites and replicated from there to our server) The ...
1
vote
1answer
107 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
350 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
vote
2answers
139 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
votes
1answer
45 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
135 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). ...
2
votes
2answers
42 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 ...
1
vote
0answers
27 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 ...
2
votes
1answer
201 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
47 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
votes
1answer
47 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
votes
0answers
27 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
22 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
votes
1answer
73 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 ...
1
vote
1answer
69 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
vote
2answers
109 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
68 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
vote
1answer
762 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 ...
1
vote
0answers
101 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
2k 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 ...
1
vote
0answers
28 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
vote
0answers
47 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 ...
1
vote
1answer
219 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
votes
0answers
5 views

Delete fabricante_producto_solicitud only if is not related to modelo_marca_producto

I have this related tables: It's possible, in one query, check if fabricante_producto_solicitud has relation with modelo_marca_producto or do I need to rely on programmatic way? I need some ...
0
votes
0answers
46 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
votes
0answers
183 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
votes
0answers
69 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 ...
0
votes
1answer
172 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. ...
3
votes
1answer
287 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 ...
1
vote
1answer
32 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
113 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 ...
2
votes
1answer
110 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 ...
0
votes
0answers
26 views

Aggregate query on indexed field slows down due to WHERE clause. Can I speed it up?

I have a MySQL InnoDB table with about 33 million rows. It has an indexed 'date' column. CREATE TABLE T ( `Id` int(11) NOT NULL AUTO_INCREMENT, `date` datetime DEFAULT NULL, `Version` ...
2
votes
1answer
442 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
188 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
47 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
votes
0answers
123 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
103 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
217 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, ...