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

learn more… | top users | synonyms

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
1answer
85 views

How can I improve performance of update query in PostgreSQL

I have a table with about 80 million records. I have added a new attribute (heigth_category) which I want to fill based on another attribute (heigth). If the heigth is between 0 and 6, I want to fill ...
1
vote
2answers
273 views

How to avoid timeouts during big DML operations

I have a big insert script I need to run. Its about 55,000 records and 160 columns. The script is already created and I can't create it again. The problem I have is that this runs for about 4 hours ...
1
vote
1answer
1k views

Splitting a column to normalized table

I have a de-normalized table as Original De-Normalized Table id text 23 first,second|third,fourth,fifth|sixth I want to normalize the database to create the following tables Table 1: (Split by ...
1
vote
1answer
317 views

query optimization delete nested query [closed]

Can the following query be optimized ? DELETE FROM COLOR_TAGS WHERE COLOR_PROJECTID = $id AND NoteID IN( SELECT ID FROM note_note WHERE BibID=$bid AND isdel=0);
1
vote
2answers
218 views

Is possible to optimize this query or it's already optimized?

I've three tables: default_users, default_profiles, default_friend. This are the SQL for each one: -- -- Table structure for table `default_users` -- CREATE TABLE IF NOT EXISTS `default_users` ( ...
1
vote
1answer
66 views

Queries not Running in Prod [duplicate]

I've an update statement which uses 2-3 tables. It runs in less than a second in QA but it takes forever in Prod. The number of records are exactly same and all the indexes are same too. In fact Prod ...
1
vote
1answer
56 views

Complex key performance problem (MySQL, InnoDB)

A query is painstakingly slow in both production environment and (fortunately reproducable) on my local dev box. Production is Linux and my dev is currently Windows 10 with MySQL 5.7.11: SHOW ...
1
vote
1answer
56 views

Stored procedure running for a long time

We have a stored procedure which is running for ever, whereas when it is run as script it takes just couple of minutes to complete. When I just declare the params and assign values to them and run the ...
1
vote
1answer
49 views

SQL getting IDs from one table with multiple entries in another table

In my database I have two tables: Persons and PersonAttributes. One Person may have several Attributes associated with it. What I would like to do is get a list of all Persons(/IDs) that have at ...
1
vote
1answer
40 views

How to optimize query with max on Postgres?

I'm trying to make a relatively simple query, but it's taking much longer than I'd expect. I have an index in place, but it doesn't seem to be helping much. Here's the query. It takes over an hour ...
1
vote
1answer
78 views

how to check whether or not queries are doing partition elimination when accessing my partitioned table?

I am considering partitioning a table. I am trying to think in terms of how we query that table so that I achieve partition elimination. Suppose I have a table that has a partition by month, what ...
1
vote
1answer
74 views

How to measure I/O contention after adding calculated fields on indexed views to a table in SQL Server?

I have successfully added several calculated fields to different tables, for example: ALTER TABLE dbo.tblBGiftVoucherItem ADD isUsGift AS CAST( ( ISNULL( CASE WHEN ...
1
vote
1answer
43 views

optimise my.ini for key query

I have a database system with a fairly complex dashboard query. First of all the details. Data model: DROP TABLE IF EXISTS `contract`; CREATE TABLE IF NOT EXISTS `contract` ( `id` int(11) NOT ...
1
vote
1answer
87 views

Int comparison very slow in query

I have this for simplicity fictional table which explains my problem: CREATE TABLE IF NOT EXISTS `posts` ( `pid` int(11) NOT NULL AUTO_INCREMENT, `user` int(11) NOT NULL, `posts` int(11) NOT ...
1
vote
1answer
96 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 ...
1
vote
2answers
198 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 ...
1
vote
3answers
438 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 ...
1
vote
1answer
126 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 ...
1
vote
1answer
48 views

stored procedures location influence their performance?

I have a procedure SP_MYPRO that updates data in MYDB1. 1) the performance of SP_MYPRO would be different if I place it in MYDB2 instead of MYDB1? 2) what if the procedure SP_MYPRO only read data, ...
1
vote
1answer
295 views

Performance of checking for data in related tables

NB: this question is purely academic / to help improve my understanding of SQL Server performance. Given a master table which relates to one or more other tables, how would you determine the best ...
1
vote
2answers
125 views

MySQL query performance question

I have a MySQL database where I would like to return results based on multiple rows. id | key | value | selector --------------------------------------------------------- 1 | username ...
1
vote
1answer
4k views

Have Postgresql query planner use nested loop w/ indices over hash join

I'm having a problem with some StackOverflow-schema related data loaded into PostgreSQL 9.3.4. I have a query that is taking about 10x longer than it should, due to the fact that it is choosing to use ...
1
vote
2answers
253 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
3answers
6k 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 ...
1
vote
2answers
205 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 ...
1
vote
1answer
421 views

MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | ...
1
vote
2answers
271 views

Need some support on MySQL Query

I have a query SELECT leads.id, sfav.id is_favorite FROM leads INNER JOIN teams tst ON tst.team_set_id = leads.team_set_id INNER JOIN members members ON tst.team_id = ...
1
vote
2answers
1k views

Mysql. Block/disconnect slow queries

I am experiencing issue. Someone 'attacked' my server: simply by searching the same phrase with multiple requests. As it is text search request and database indices are not used, the engine searches ...
1
vote
1answer
936 views

Query is not using indexes on third table in left join

My query is not using indexes on third table(pci promotion_coupon_images) . i was tried with using index and force index in query but there is no change in result. any body please suggest me how ...
1
vote
1answer
50 views

simple query is not using indexes

My query is not using indexes. it was taking around 5 seconds. output is 500 rows only. it is a simple query Please find the explain plan and table structure here. Explain Plan mysql> explain ...
1
vote
1answer
94 views

Dealing with large log files

I'm new to the database world and have recently started working with a large database with several tables with mainly varchar text and integers. The two largest tables are of ~50 million and ...
1
vote
1answer
206 views

EXISTS and sub-query cost

i've just wondered if there's a difference in cost(memory,cpu) of an EXISTS or NOT EXISTS in following queries. Does it make a difference if i select NULL, 1 or columns? 1) SELECT id FROM Parent p ...
1
vote
1answer
448 views

SQL Server 2012 Performance Test

I've been given a task to test where an SQL Server 2012 can achieve better performances - we have two options: Use the SQL Server as an On-Premise machine (Standalone server that we have) Use the ...
1
vote
1answer
1k views

Slow performance of MySQL Join Query

I have inherited a site (running Coldfusion8 and MySQL 5.0.88) with a product search using multiple criteria. I'm struggling with optimizing the search, especially a pricelist check, which makes the ...
1
vote
2answers
183 views

Can a poor database layout cause performance issues for simple queries?

I have a database layout that is realy a mess and needs to be optimized. Does the layout of the database and some queries that are executed cause other queries to be slow too? For example, an insert ...
1
vote
2answers
1k views

Update Large Table

I have these two tables: user_profile: user_profile_id_int int primary key user_profile_id varchar user_activity: user_profile_id_int int key user_profile_id varchar both fields in user_profile ...
1
vote
2answers
35 views

Slow query / Indexes creation (PostgreSQL 9.2)

I have the following Query: explain analyze SELECT split_part(full_path, '/', 4)::INT AS account_id, split_part(full_path, '/', 6)::INT AS note_id, split_part(full_path, '/', 9)::TEXT ...
1
vote
1answer
25 views

index creation - Slow Query - PostgreSQL 9.2

I've got the following query: SELECT * FROM ( SELECT split_part(full_path, '/', 4)::INT AS account_id, split_part(full_path, '/', 6)::INT AS note_id, split_part(full_path, '/', 9)::TEXT ...
1
vote
1answer
82 views

Why using where in indexed field is slow?

we have a big table. the table structure is : CREATE TABLE `visit_logs` ( `id` int(10) NOT NULL AUTO_INCREMENT, `user_id` int(10) NOT NULL, `ref_id` int(10) NOT NULL DEFAULT '0', `link_id` ...
1
vote
2answers
81 views

How can I improve performance on a 3 table query?

I'm attempting to analyze a resource drawdown (the percentage of time individual units are being utilized during a reporting period, e.g. 2-weeks or 1-year). I need the aggregation down to the ...
1
vote
1answer
56 views

Extra fields in user_role / roles tables or a new table

I have a user_roles table which I use to manage permissions and user's access to certain things. For example, a team manager is a role. Since a team manager belongs to a specific team, the way I ...
1
vote
1answer
68 views

get query execution time in command prompt [duplicate]

I'm doing this query select * from rentals. This table has more than 10,000 rows and it takes more than 4 minutes to retrieve the results. But I get this time after I get the results: 10000 rows in ...
1
vote
1answer
82 views

MySQL difficulty with optimizing slow query with index but without improvement. Explains tells otherwise

I've a slow query (~11 seconds) that I'm trying to optimize. But the use of indexes seems to not make any difference even thou Explain indicates otherwise. Let me walk you through my problem. So this ...
1
vote
1answer
46 views

How can I 'further' improve my table and queries

This question is an extension of this question. Where Rick James kindly provided a list of things I should change in my table and query. I also changed my application so that unused filters weren't ...
1
vote
1answer
104 views

SELECT Causes Performance Issue [closed]

I have a SQL SELECT statement that has joins on 27 of our warehouse tables. Original statement was taking more than an hour everyday so I decided to optimize it. I created some indexes but still it ...
1
vote
1answer
27 views

What are the consequences of enabling slow_query_log and flushing the cache on mysql?

I have a large database that is performing poorly recently. I want to enable the slow_query_log to investigate the queries and flushing the cache but I need to know what are the consequences of doing ...
1
vote
1answer
65 views

Does InnoDB store row counts in secondary index B-Tree non-leaf nodes?

Does InnoDB store row counts of child nodes in secondary index B-Tree non-leaf nodes? If so, does MySQL use this information to speed up COUNT(*) queries with range constraint (assuming appropriate ...
1
vote
2answers
350 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 ...
1
vote
1answer
106 views

Speed up COUNT(*) when using an index

I have a table similar to this (simplified): CREATE TABLE books ( id INT AUTO_INCREMENT, category INT NOT NULL, PRIMARY KEY (id), KEY (category) ); This table has over 10,000,000 ...