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

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2
votes
2answers
799 views

Why does innodb_flush_method = O_DSYNC provide such a performance boost with SAN-backed storage?

I've seen some people suggest that O_DSYNC should be used with a SAN. The MySQL docs have this to say about O_DSYNC in general: In some versions of GNU/Linux and Unix, flushing files to disk with ...
0
votes
1answer
456 views

NTEXT,Indexing, and lob logical reads

We have an query that would benefit from a covering index but one of the columns that would be returned is a NTEXT data type. I know this can't be added to the index and I also know it would be good ...
4
votes
2answers
854 views

Why is my plan guide not being used?

We recently ran into the tipping point issue and some of our report queries that used to complete execution within a couple of seconds are now taking more than 2 min because the query optimizer simply ...
1
vote
2answers
234 views

Why does “SELECT *” take longer than “SELECT <primary_key>”?

I'm having a problem with a query running on a little PHP program. When I use * to select all the columns, it takes way more to return the result than when I use just one column. The query that is ...
1
vote
0answers
26 views

Difference in the workload related to data-amount and search option

A couple of days ago I was asked why it is necessary to use the first normal form also for separation of names. We have a table which stores private customers (Name+Surname;Information) and business ...
1
vote
0answers
208 views

Latest of group in subquery is bottleneck, how to optimizing query?

See Original question I'm fetching the activity data for the latest activity for each company as part of a bigger query. I've been using the method provided by ypercube, and it works fine, but I find ...
1
vote
1answer
406 views

Retrieve next queue item

I have a simple table in SQL Server 2012 which implements a processing queue. As data has been inserted the query to retrieve the next item has gone from <100ms to a constant 5-6secs. I would be ...
2
votes
0answers
571 views

mariadb out of memory crash

I have recently migrated from mysql (5.5.36 MySQL Community Server (GPL)) to MariaDB (10.0.10-MariaDB-1~wheezy), along with switching my cloud hosting provider. Both machines have 2GB RAM and 1GB ...
1
vote
1answer
10k views

MySQL SQLSTATE[HY000]: General error: 1205 Lock wait timeout exceeded

I have database session enable, when website got thousands of visitor. It gives me error [30-Apr-2014 04:27:12 America/Denver] PHP Fatal error: Uncaught exception 'PDOException' with message ...
3
votes
2answers
265 views

How can I eliminate this costly index seek operation from my query?

I have two tables in Sql Server 2008 that look something like this: Transaction_Details: Dataset, Department, Charge_ID, Transaction_Type, dos_month, post_month, amount ...
3
votes
2answers
4k views

MySQL COUNT Query taking too long time to execute

I have below query that takes 7 secs to run SELECT COUNT(*) AS `count` FROM `yuldi`.`businesses` AS `Business` LEFT JOIN `yuldi`.`businesses_categories` AS `BusinessesCategory` ON ...
4
votes
0answers
610 views

SQL server query is slow *without* including execution plan [closed]

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 ...
0
votes
0answers
63 views

MySql query keep running for a long time

Following query keep running for a long time and I'm using MySql 5.5.34 on XAMPP on Windows SELECT id_package, `pck`.`fk_sales_order`, `pck`.`fk_picklist`, count(pci.id_package_item) as items, ...
0
votes
0answers
77 views

Adding additional condition significantly degrades performance

Have the following query: SELECT * FROM table_A INNER JOIN table_B ON /* conditions */ INNER JOIN table_C ON /* conditions */ INNER JOIN table_D ON /* conditions */ WHERE table_B.state = 'active' ...
3
votes
1answer
181 views

How do I deal with query getting slower when a select parameter is not specified inline?

I faced this problem twice with SQL Azure and two different queries so far. Something like this: select top(100) * from SomeView WHERE AccountId='actual-guid-typed-in-here' runs super fast but ...
2
votes
2answers
248 views

DISTINCT not using an index [duplicate]

I have table (2139868 rows): COLUMN1 NUMBER(20,0) COLUMN2 XMLTYPE COLUMN3 XMLTYPE COLUMN4 VARCHAR2(50 BYTE) COLUMN5 VARCHAR2(50 BYTE) COLUMN6 VARCHAR2(50 BYTE) COLUMN7 VARCHAR2(50 BYTE) COLUMN8 ...
1
vote
1answer
85 views

Any idea why this seemingly-simple query is really slow?

Here's the query SELECT count(*) FROM registration r LEFT JOIN registration r2 ON r.baggage_group_id = r2.baggage_group_id AND r2.team_id IS NULL WHERE r.event_id = "102577"; It seems pretty ...
1
vote
2answers
1k views

postgresql being slow on count distinct for dates

I have a very simple, but very big, table. Its schema is like this (yadda int, yadda1 int, yaddate date, ... other stuff). Now, yaddate has an index by itself and it is also in other indexes ...
1
vote
2answers
285 views

What's the best way to translate a website [closed]

I have a website in Django using MySQL, and I have more than 4.000 entries that I want to translate. What's the best way to do it? Create a new database for every language? Create other table for ...
1
vote
0answers
59 views

Microsoft Access database performance

I wonder how MS Access manage to show long list of records when we want to browse theme in Datasheet view. 1 - Does it load limited amount of records on start-up and then load the remainder upon user ...
1
vote
0answers
232 views

Best database for fast read all in one table [closed]

I currently have a large database in SQLite that I was using for rapid-prototyping for a software I am working on. Now that I am planning to move it to another database that should give better ...
0
votes
2answers
177 views

How to optimize query

I'm 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 ...
0
votes
2answers
3k views

How to fix slow LIMIT queries with big offsets without heavily rewriting them?

Imagine a very basic example of your average discussion board. For example: CREATE TABLE threads ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, title VARCHAR(100), PRIMARY KEY (id) ) CREATE ...
1
vote
3answers
5k views

Is table partitioning improving performance? Is it worth it?

I have just been involved in a project on which I will have to develop a data migration process and a web interface that uses an already existing SQL Server DB. This DB was developed by another person ...
0
votes
0answers
147 views

Big Mysql table optimization

I have a table that I use to cache google translate API answers. Table structure is orig_string and group are indexes Now it has more that 1million rows with 35000 distinct values in group field. ...
4
votes
1answer
156 views

Every query plan statistic says my query should be faster, but it is not

I have a bit of a odd situation. I have two queries that produce the same result, according to SSMS and SQL Sentry Plan Explorer the first query should cost 95% and the 2nd query should cost 5%. ...
1
vote
1answer
2k views

How can I speed up a Postgres query containing lots of Joins with an ILIKE condition

I have an odd problem which I really don't understand. Simply put I have a join containing 4 table joins, which I believe all have appropriate indexes, but which takes a ridiculous amount of time to ...
1
vote
2answers
186 views

Oracle result cache behaviour

Oracle by default caching the query results and function results(Buffer cache). I have noticed this with AutoTrace utility, where the physical reads are huge on first execution, but from next ...
0
votes
2answers
171 views

Get only future records

I have the following query: SELECT master.master_id, master.showname, MIN(CONCAT(shows.show_date, ' ', shows.show_time)) AS first_show_date, MAX(CONCAT(shows.show_date, ' ', shows.show_time)) AS ...
3
votes
1answer
829 views

Is there any way to get the estimate cost of executing a query in MySQL?

In PostgreSQL, EXPLAIN or EXPLAIN ANALYZE will show the estimate cost of executing a query. But EXPLAIN in MySQL doesn't provide this information. How can I get the estimate cost without installation ...
0
votes
2answers
76 views

MySQL query optimization for legacy application

I'm working with a legacy application that started out with little data years ago (developed by a third party custom for this client), and now we're seeing MySQL load skyrocket on this query alone. ...
0
votes
1answer
656 views

Take query results and insert into new table [closed]

So I have the following query: DECLARE @tbl TABLE(value int) *--The same function but with the number of the random numbers ;WITH Nbrs (n) AS ( SELECT 1 UNION ALL SELECT 1 + n FROM ...
2
votes
2answers
2k views

Optimized query to fetch a record from 10 million entries

A table has 2 fields | UniqueKey | TimeStamp | ------------------------- | xfsddddq | 1024125412 | | xfstttdx | 1024125413 |< | xfsdxxau | 1024125415 | Estimated, there are 10 million ...
3
votes
0answers
69 views

Tagged questions

I have similar to StackExchange network that utilises tagged questions. In my web application Users also can find questions by tags. The query below returns a set of tagged questions: SELECT ...
0
votes
1answer
333 views

too many entries for one single session and serila# in V$Session_longops

I have a concern with the entries in v$session_longops. I used a query to identify query running from past 25 minutes for sid=62 which is given below: SELECT s.sid, s.serial#, ...
1
vote
1answer
2k views

Poor performance on inner join using dates and between

I am having trouble optimizing a query that does an inner join using a date range. The purposes of the query is take daily data and summarize by week. Select pcw.EndDate WeekEndDate, h.Store, ...
4
votes
2answers
306 views

Query tuning to meet timeout settings [closed]

We have an web app with a 30 second time out on search screens. I've analyzed the original query and added a missing index for one of the query's 9 joins. Other things like expected and actual ...
0
votes
0answers
162 views

Oracle Merge performance

I've a question about the merge performance in oracle. I work in the business intelligence area of a big company and its quite common to have to move millions of records one side to other. The other ...
12
votes
3answers
2k views

Indexes for SQL query with WHERE condition and GROUP BY

I am trying to determine which indexes to use for an SQL query with a WHERE condition and a GROUP BY which is currently running very slow. My query: SELECT group_id FROM counter WHERE ts between ...
1
vote
0answers
112 views

MySQL query with order by decreased performance

Here is my schema: CREATE TABLE `UserMst` ( `UserID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT, `EMailID` varchar(50) DEFAULT NULL, `UserName` varchar(20) DEFAULT NULL, `FullName` ...
0
votes
0answers
224 views

Remote scan in OpenXMl

I'm looking for some advice on OPENXML. Specifically, the performance. I am seeing very slow performance on a very small piece of XML. Something about this is causing a Remote Scan. Any ideas on how ...
1
vote
2answers
341 views

optimization of expensive subquery

The following query gets the last report (where latitude and longitude and secs are <> 0) associated with the specified units: SELECT reports.* FROM reports INNER JOIN ...
7
votes
2answers
15k views

High CXPACKET and LATCH_EX waits

I am having some performance issues with a data processing system which I am working on. I have gathered wait stats from a one hour peroid which show a large amount of CXPACKET and LATCH_EX wait ...
0
votes
2answers
1k views

How can I speed up this query on table with 65 million records

select hash_id, hash_value, substring(T.cri, 1, 7), substring(T.cri, 9, D2.Pos-9), substring(T.cri, D2.Pos + 1, D3.Pos - D2.Pos - 1), ...
0
votes
1answer
864 views

Delete millions of rows, fast

I currently have a database with the following structure: id->varchar(9) time->datetime val01 - val20->int(11) val21 - val40->tinyint(1) id and time are the primary key. also I defined an index ...
0
votes
2answers
421 views

Instead of static list, using a table select result for IN key

I use a static list for some queries WHERE clause like WHERE STypeID IN ('12', '13', '14', '265') This list will be changed in the future; new values will be added. When list changed, I don't want ...
0
votes
1answer
151 views

Query causing Database lock problem (php/Mysql) [closed]

What is the issue with my query? When I execute, it lock the database for 5 to 10 minutes. Please help me to optimize this query. SELECT u.username, u.email, u.created_at, ...
1
vote
1answer
290 views

Firebird query performance with text search, also some numbers

I have situation as follows: I'm having a table OFERTY of 10k+ records, and when I select * from it, I get PLAN (OFERTY NATURAL) Executing... Done. 656 fetches, 0 marks, 0 reads, 0 writes. 0 inserts, ...
0
votes
2answers
60 views

Which one is better way to insert data? [closed]

I have two cases case create proc createEmployee @firstName varchar(255), @lastName varchar(255) = null as insert into Employee_Tbl values (@firstName, @lastName) case create proc ...
4
votes
2answers
243 views

Spatial index not used

I have a table with a geometry column. For one record, there is only one Point stored. A spatial index has been created but queries searching for the nearest location do not use this index resulting ...