In the context of a database, optimisation refers to the process of the query optimiser selecting an efficient physical execution plan.

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Optimising a query to get rows where x is between pairs of values from another table

PostgreSQL 9.4.5 In my database there are 2 tables, vcfentries and exons. I want to query for rows in vcfentries where pos is between a list of pairs of positions, exonstart and exonend in the ...
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What are the things that you will look at execution plan [closed]

I can write some good queries and I am trying to understand reading execution plans and see if there can be a better plan for this query. Below is the checklist I derived over time from different ...
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3answers
71 views

Improving query time for auto complete box with millions of record

I have a very basic requirement. I have a table that store city id (primary key) and city name (nvarchar value). The remaining information is stored in a separate table. In my UI, I have an auto ...
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44 views

Slow query - PostgreSQL 9.2

I've got a Query that takes some time to be executed... Can you guys help to improve the total time? Thank you! QUERY: SELECT file.inode_id AS file_id, file.parent_inode_id AS ...
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62 views

How does logical and physical operators of query plans works in low level? [closed]

As a practice a few weeks ago I decided to build a small database system. I wrote relational tables as object arrays. Also I wrote basic relational algebra operations that operate on my data ...
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36 views

Most Similar Records Query Performance

I have a mysql database table with 20 million records. It grows at roughly 25,000 records per day. Each record has a number of numeric fields. I have a similarity query that selects the 10 most ...
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1answer
58 views

Optimizing query in PostgreSQL that tries to match a string and matches a timestamp range

I am building a database in PostgreSQL for financial data, where the table looks like this: create table fin_data( brokerid text, stock int, holding bigint, stake float, value ...
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16 views

Variables for Merging MySQL InnoDB Tables

I have several thousand InnoDB tables in MySQL 5.6 that I am trying to merge together into a single table. A simplified form of the queries I am executing (one for each of the tables to merge) is ...
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1answer
59 views

How can I find out what stats objects were used during a SQL Server 2014 query?

I’ve read here that trace flags 3604, 9292 and 9204 enable debugging output that shows what statistics objects were used by the cardinality estimator during query compilation in SQL Server 2012. They ...
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86 views

Queries which return more than 100k rows

I have a following query SELECT * FROM table_name WHERE #3_column BETWEEN start_date AND end_date which is taking about 10 seconds on my computer to execute and returns about 180k rows. Table schema ...
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1answer
485 views

MySQL Query with good execution plan is very slow due to Sending data operation

I have the following query: SELECT a.borrowerId AS borrower_id, a.created, NULL AS initiator_team_id, NULL AS initiator_user_id, NULL AS old_team_id, NULL AS old_user_id, ...
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PostGIS Intersects Query takes lot of time to get the result

I am developing a webmapping application in which I used PosgreSQL with PostGIS plugin as my DB. I have this two tables namely; evidensapp_polystructures and evidensapp_seniangcbr. Both tables ...
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48 views

Oracle tuning strategy for columns with long tails

We have an Oracle 11g database, where the two biggest tables are Customer and Order. The order profile of our customers has a long tail: we have millions of customers, with most only having a small ...
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23 views

Optiming ACT_RU_JOB Query

We're using Activiti version 5.15.1 with timers in our workflow which sends reminders to users who are in the workflow. Problem is that we're creating jobs in ACT_RU_JOB table and even though there ...
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310 views

Why my sql query run faster than my stored procedure?

I am trying to write a script in MYSQL Workbench to update my database every day using stored procedure but I find it too slow compared normal query or temporary tables. If i use temporary table the ...
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434 views

Oracle 10.2.0.4 query hundreds times slower than the same query on Oracle 10.2.0.3

I have an issue with query on Oracle 11.2.0.4.0 (it takes forever to complete and CPU is at 100% all the time) so I was trying to change optimizer_features_enable to previous versions. It worked with ...
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66 views

MySQL Cluster 7.4.6 - Analyze table failure on 15m reference table

I'm running MySQL Cluster 7.4.6 on Azure VM's with the following infrastructure: 2 x Mgmt Nodes: Ubuntu 14.10LTS, 2 cores, 3.5GB ram 2 x MySQL API Nodes: Ubuntu 14.10LTS, 2 cores, 3.5GB ram 2 x Data ...
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208 views

Optimizing a geo search in Postgres

I'm searching for UK postcodes within a radius of a given postcode. The query that I'm using looks like this: SELECT *, earth_distance(ll_to_earth( {$lat}, {$lon} ), ll_to_earth(lat, lng)) as ...
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26 views

Optimizing MySQL for write throughput ceiling

We have a large MySQL database on AWS RDS, with a huge table around ~1.8TB with massive write workload. We recently hit a write throughput bottleneck, which caps our provisioned IOPS way below the ...
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62 views

Is there a way to improve this query further?

I've got a query that over time I've been improving. Originally it simply selected * from the records table, and the data was formatted on the webapp side. But that was slow and I wanted to make ...
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1answer
69 views

What is causing an INTERSECT to run forever when the individual SELECTs run quickly? [closed]

I have a script that applies the INTERSECT operator to 2 separate queries. Query1 executes instantly and returns ~1k rows. Query2 executes almost instantly and returns 200k rows However, when ...
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1answer
131 views

Multi table GROUP BY query optimisation

Currently I have a multi table/column GROUP BY query which is pretty slow. Below is the tables schema used by the query: report Table ...
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158 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 ...
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1answer
26 views

How to optimize search restricted by boolean column?

I want to optimize a query1 of the form SELECT yid, xid FROM x WHERE is_principal; Here, is_principal is a non-null boolean column of x. If I run EXPLAIN QUERY PLAN on this query, the output I get ...
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1answer
44 views

How to get paged resultset from a table?

I am trying to get paged resultset from a table (Notes). So, I am passing the last offset id (@LastOffset) value along with the page size (@Count). My approach to achieving this is: Sort the table ...
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469 views

Optimize large table design

First, I am a complete novice when it comes to databases, but have been given the task to speed up queries on a large set of data. (Hundreds of millions of records) The current implementation is a ...
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1answer
175 views

optimize design for a table with 50 columns [closed]

I have a table with 50 column and one of my friend has told me to split the table in 4 different table to save 12 column in each table. He proposed a design to have Master table and refer the PK of ...
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106 views

Delete Query throwing warning db2

I am trying to delete multiple records from view The view has Instead of Trigger defined .. The view has records consolidated from multiple tables. [db2inst1@testServer001 ~]$ db2 "delete from ...
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359 views

How to Insert records from remote database to local database using dblink in postgresql 9.3

I have a scenario like i have a two DB, one resides in remote server and other resides local. Now i have to fetch the records from remote DB when new records are inserted on tables (in remote DB) and ...
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1answer
844 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 ...
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56 views

Slow MySQL Query when Ordering

This query takes around 2 seconds when the order by is included, without the order it takes less than a tenth of a second. The field that is doing the sorting, qc_products.addedDate, is an index and ...
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75 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, ...
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1answer
104 views

Is it normal that I have to FLUSH QUERY CACHE once every 6 hours to maintain fast queries?

I am running MySQL 5.5.37. I have a cronjob set to run every 6 hours to flush the query cache. I realized that if I don't do that, then the cache becomes fragmented and average query response time ...
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856 views

MySQL InnoDB log files on different location

I am using MySQL version: 5.5.38 There are following parameters that can control InnoDB log files: innodb_log_files_in_group - amount of log files in the group, by default 2. Will create 2 files ...
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733 views

Optimization Tips For MYSQL Tuner/Primer

So I have a site that has a crap ton of traffic. I see a decent amount of latency when the site has over 1,000 active visitors on it. I have new relic installed and it seems Im only using 10% of the ...
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136 views

Refactoring IN Subquery, Avoiding Query in a Loop

I've got a table which was designed as both the current data set for participants, as well as being the historical changeset for those participants. This table has been in use for approximately three ...
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Need help in optimizing a Slow Query

I am using userpoints module to provide points for different actions that they do on my site. mysql> desc userpoints; +-------------+---------+------+-----+---------+----------------+ | Field ...
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Querying number of tries since last successful log, checking IP as well as user

I asked this question before on stackoverflow, but it might fit better here, since it is mainly about database performance. The actual question With performance in mind, how would you go about ...
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164 views

Significant difference between duration for querys in SHOW PROFILE and SHOW PROFILES?

I have use mysql profiler to optimize an opencart query which takes more than 10 seconds to executes. mysql> SHOW PROFILES; +----------+-------------+-----------------------------------------------...
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1answer
6k views

Truncating Table Partitions Containing Data and Global Indexes

I have to truncate a partition (392,000 records) of a table with 20.000.000 records. At the moment, I'm making a truncate table and rebuilding indexes. But the table has 37 indexes and it takes 20 ...
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343 views

Why is adding a FK constraint slow in MySQL?

I'm doing some experimentation in MySQL 5.1.53 and I've run across a case that I just don't understand. CREATE TABLE A ( `pk` INT(11) NOT NULL, `fk` INT(11) NOT NULL, PRIMARY KEY `pk_A` (`...
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116 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` ...
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94 views

Query optimization, SQL Server cache query, SQL Server execution query

I have 2 queries, the results of their execution is the same, but I don't know which of these is the best in terms of performance and why. Query #1: SELECT CASE WHEN ( EXISTS (SELECT 1 AS [C1] ...
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681 views

is it good to add index on column used in group by clause?

I have a query like- select x, sum(y) from xyz where z>=100 group by x order by sum(y) desc; will it be faster if I am going to add index on x?
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can this mysql query be optimized further?

I have this query select counterparty_id, max(id) max_id from client_administrations where counterparty_type = 1 and effective_on <= '2013-10-22' group by counterparty_id When I ...
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605 views

Optimising a query of an SSRS dataset

Consider the query given below: SELECT * FROM ((SELECT c.cust_id , c.username , REPLACE(qs.seg_type_ref_key_02, 'N/A', 'Non Vip') casino_group, ...
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Mysql key_buffer_size already 16GB but some fulltext searches are still slow

I have a query w/ full text search which takes 5 - 10 secs. key_buffer_size is already 16GB. Table has 15 million records and has a compound fulltext index on fields: categories and company. Table ...