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

learn more… | top users | synonyms

16
votes
2answers
20k views

Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries

I have a PostgreSQL 9.2 instance running on RHEL 6.3, 8-core machine with 16GB of RAM. The server is dedicated to this database. Given that the default postgresql.conf is quite conservative regarding ...
1
vote
0answers
31 views

How can I replace the below logic for my Stored Procedure?

I have a table named TagSchema that stores information flattened from XML. The data in this table is stored per item. I have to get the data from this table and process it per item. I wrote a job ...
0
votes
0answers
8 views

MariaDB: Querying a timestamp partition

I'm having difficulties getting my queries to make use of the partitions when I'm selecting. They need to be able to do > sometime > sometime and between sometime and anothertime. However, if I ...
0
votes
1answer
22 views

Record scan speed, column orientated databases and SSDs

I'm learning about column orientated databases. I have just watched a YouTube video on column orientated databases by Arnaldo from MIT, who suggests an interesting motivation for column orientated ...
1
vote
2answers
67 views

Slow SQL query with LEFT JOIN

What my query is doing: I have two SQL tables and I want to copy datarows from the one table to the other table. I am doing this for statistics. The source table includes all current ...
0
votes
1answer
46 views

How to improve this query so it'll run quicker

I've got this query: SELECT m.vlanID, v.vlan_name, m.interfaceName, count(m.macAddress) as mac, n.nd_name, p.interfaceDescription, p.interfacePortType FROM macs m, network_devices n, ...
4
votes
1answer
27 views

Update queries slower after enabling SQL Server Full-Text Index

I have an asp.net website with many insert, update, and delete queries running against my database. A few days ago I create a Full-Text Index on two columns of one of tables. After that I realized ...
0
votes
1answer
42 views

Artificially increasing query time

Very weird question: Is there any way to artificially inflate the amount of time a query will take? An infinite loop would be great. SELECT CLAIM.UNIT_PRICE FROM CLAIM WHERE ...
4
votes
1answer
114 views

Finding distinct rows across two tables: Full Outer Join more efficient than Union?

When finding distinct rows across two tables where we can't necessarily ensure are pre-sorted, is it a good idea to use a FULL OUTER JOIN rather than a UNION? Are there any downsides to this ...
5
votes
3answers
64 views

Slow query performance due to temporary file?

Here is the query: SELECT "products".* FROM "products" WHERE (status > 100) AND "products"."above_revenue_average" = 't' AND ("products"."category_id" NOT IN (5)) ORDER BY ...
0
votes
0answers
32 views

MySQL: Slow Query Performance - Parameter Sniffing?

For a personal weather project, I am trying to define and run the following stored procedure: DROP PROCEDURE IF EXISTS history_between$$ CREATE PROCEDURE history_between (IN date_start DATETIME, ...
0
votes
0answers
41 views

Mysql query performance is really bad

I have a very simple query in MySQL which is taking hell lot of time. It ran for 18 hours and didn't complete Update OrderDetail OD Join TEMP_PARTMASTER_LATEST_UPDATES PM Using ...
2
votes
1answer
137 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 ...
2
votes
2answers
2k 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 ...
2
votes
1answer
42 views

how to find the T-SQL of a sleeping session that is blocking some other process?

I have a stored procedure called sp_radhe that I put on my servers and it has been helping me to "see" what is happening internally. here is the code of this stored procedure: USE [master] GO SET ...
1
vote
0answers
22 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, ...
8
votes
1answer
418 views

What does duration measurement in sql server actually measure?

What precisely does the query duration measure when conducting a profiler trace? I have a stored procedure which performs data access (SELECT), and it is taking an average of around 30 seconds to ...
2
votes
2answers
40 views

Finding differences between two tables takes too long

I'm trying to find the diff of two tables using a left join. My query is as follows: CREATE TABLE my_diff (INDEX my_index (name, type)) SELECT AA.name, AA.type FROM AA LEFT JOIN BB USING (name, ...
3
votes
1answer
111 views

Query looks optimal but logical reads is huge

I run the following (really simple) query in SQL Server: SELECT MAX(PK_Field1) FROM MainTable kh WHERE kh.PK_Field1 >= '2014-12-01T00:00:00' AND kh.PK_Field2 = 1572 AND ...
0
votes
1answer
27 views

Is it advisable to asynchronously update the summary table every time a transaction is deleted?

Given three tables: (a) Product (b) Transaction Head (c) Transaction Detail We need to create a query that fetches a list of products with associated latest ordered quantity and latest transaction ...
1
vote
2answers
47 views

How to optimise MySQL query that uses dependent subquery

I have a web app that has a custom feed of images. The image queried are based on whether the users have previously seen the image and ordered by a Hacker News style score. There are only 1000 rows ...
1
vote
1answer
45 views

Slow MySQL query when the IN list is long

I have 3 tables, namely: product, product_has_category, category: CREATE TABLE IF NOT EXISTS `product` ( `id` int(11) NOT NULL, `name` varchar(255) DEFAULT NULL, `des` text COMMENT 'description', ...
1
vote
0answers
199 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 ...
5
votes
2answers
402 views

Grant users privilege to use QUERYTRACEON 9481

Microsoft suggests using OPTION (QUERYTRACEON 9481) for queries that have "degraded" performance against SQL Server 2014 databases running under compatibility level 120. In my situation, "degraded" ...
1
vote
1answer
40 views

Is it more efficient to union from sub-query or combine two outer queries?

I searched for this but couldn't find the response I needed. So my apologies if this has already been asked. I'm asking in regards to DB2 but I suppose this would apply, generally speaking, to just ...
1
vote
1answer
21 views

How to merge partitions in Postgres?

I have a table that is partitioned by date on a monthly basis beginning January 1, 2014. There is significantly more rows of data in 2015 than there were in 2014 and the data in 2014 is not accessed ...
1
vote
1answer
150 views

Tuning Mysql and Monitoring

I would like to know if anybody can point me towards a tool/way for MySQL database tuning. Actually the tuning of my.cnf is like below: My database engine is MyISAM | Mysql 5.1.73 key_buffer = ...
0
votes
0answers
41 views

Upsert - Should I verify the row exists first, attempt an update, or try to insert first?

In a software that I'm working, I have a table with a few columns and a id. In some events in my software, I need to update some column of a record with a certain unique field (other column), but ...
2
votes
1answer
114 views

why this session in particular is suspended? Please see the details

My understanding regarding the suspended status of a session: A query gets suspended when it is requesting access to a resource that is currently not available. This can be a logical resource ...
2
votes
2answers
63 views

MySQL: memory requirements for django app with 1 big table (460M rows)

I have created a django app that is running on virtual machine. All db tables are rather small (up to 1M rows) but recently I was asked to add a big table (460M rows). CREATE TABLE `genescorrelation` ...
5
votes
1answer
56 views

Joining in query decomposition

I have a question about query decomposition and localization, as in here: When joining 3 tables (here EMP, ASG and PROJ) is there any specifiy order, when to join which table? Why ASG and EMP are ...
3
votes
0answers
74 views

query optimization of a left join

I have the following query written into the slow log (mysql-slow.log). I don't have much idea how to optimize this query. I already have indexes for: mode, f.user_id... etc but doesn't seem to ...
2
votes
2answers
206 views

How to optimize indexes on MySQL query with various sorts

I have an INNODB table levels: +--------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | ...
4
votes
1answer
85 views

Performance problems with TOP and user defined functions in views

I have problem with performance of queries on simple query on view. To keep things simple, assume my view is defined as follows: CREATE VIEW [mon].[ViewDevicesWithGroups] AS SELECT Id, Name, ...
3
votes
1answer
73 views

Problem with clustered index? Or bad indexes? (SQL Server 2008 R2)

I have this query (it was running in 2 minutes). With new indexes, it takes 40 sec: This is the execution plan: [![100% use][1]][1] [![it's not heavy][2]][2] [![not at all][3]][3] I can't ...
1
vote
1answer
34 views

Monitoring SQL Server 2012 slow queries/queries which are causing blocking

I am using SQL Server 2012 and I want to get hold of the queries which are taking longer to execute along with the queries which are causing blocking on the server. When I look at the server for the ...
1
vote
1answer
134 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, ...
2
votes
4answers
149 views

Finding all date ranges that overlap a target date range

Say I wish to store when staff are on holiday (FromDate, ToDate) and then I wish to find all staff that are on holiday between two given dates (QFromDate, QToDate). Now assume that I have many such ...
0
votes
0answers
32 views

How should massive effect update queries and scripts be performed?

I have some MongoDB databases in production (at a Mongolab AWS deployment) for which I've sometimes required to apply queries or scripts effecting on whole collections. As collections got over 20k ...
-1
votes
2answers
55 views

Optimize query or split in two queries and process result separately?

I have this DB schema: As you may notice already there is no relationship between tables and won't be on the future. If I run the following queries I will get a lot of rows per table: SELECT ...
2
votes
2answers
242 views

Why the WHERE clause is not pushed down in the view's query?

With Postgres 9.4, I'm doing the following query quite often: SELECT DISTINCT ON(recipient) * FROM messages LEFT JOIN identities ON messages.recipient = identities.name WHERE timestamp BETWEEN timeA ...
2
votes
1answer
148 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) ...
2
votes
1answer
52 views

Any SQL where clause performance similar to where 1=0

(i'm using SQL Server 2008R2 or later) For centralize manage and consistent, there is a view definition as follow: CREATE VIEW view_all_situation ( select null as src, tf.col1, sum(col2) as fee, ...
3
votes
1answer
400 views

Getting each status change in a table

I have a table that holds status changes per item. The item can go in and out of a status multiple times. ItemTable (ItemId int, Status varchar(50), DateOfChange date) I need to pull the date of ...
1
vote
1answer
478 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 ...
3
votes
0answers
39 views

Efficiently computing aggregate functions over subqueries with incremental data

I have a PostgreSQL database (version 9.3.6) containing a large number of orders. As the orders are processed, scan_events are triggered and stored, with multiple events per order. Scan events have a ...
2
votes
1answer
176 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 ...
1
vote
1answer
62 views

Postgres not using the index even when rows returned is 5% of the table

I have a postgres table with the following structure: +---------+-------------+-------------+----------+---------+---------+ | id | timestamp | numvalues | text1 | text2 | text3 | ...
1
vote
0answers
46 views

Tuning MySQL MyISAM for large joined updates

I have a database with two tables that I would consider small. I need to update values on the larger of the two tables (1,100,000 rows, 75M MYD, 120M MYI) from the join of the two tables. The smaller ...
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 ...