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

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PostgreSQL: labels vs columns

I have a data structure similar to this: date foo bar baz boo ---------------------------------------- 2015-11-18 1 null 2.5 81.0 2015-11-19 1 78.4 12.8 ...
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0answers
46 views

Optimizing a group by/where in/min() query in MySQL

Assume I have a table that looks like such (The actual column names of my real table would only make things harder to explain, so I have created a mimic that behaves similarly). id | cond1 | cond2 ...
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76 views

Mongodb Huge Number of Open Connections and Write Locks

We are seeing around 800 open connections to our Mongodb. To clarify our issue: We have 5 different clients who write the data into Mongodb. Each of these clients - write four different type of ...
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2answers
126 views

Faster query when joining data from multiple tables

I’m looking for a way to make a database query faster. The table parts has over 6 million rows. Each part row is associated with the manufacturers table (a couple hundred rows) by ID. When searching ...
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1answer
82 views

How to speed up queries in MySQL on a table with ~50 million rows

The table has 4 columns of type datetime, smallint(6), tinyint(4) and decimal(15,5). The first 3 columns are PK. There are four indexes on the table: one with all the PK columns, and one with each ...
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30 views

How to efficiently a query to return rows plus a summary

I need to write a query for a SQL Server 2012 database that will return rows to be presented to a search results page, this page has 12 filters that the user can use to narrow the results. I create ...
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1answer
66 views

SQL Server - High Performance Record Comparison [closed]

Scenario : I have a collection of records to be inserted/updated into a table. Each record before getting inserted/updated in the table must be checked with the other rows in the table so as to find ...
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3answers
62 views

MySQL: Why is this UPDATE query so incredibly slow?

So I have a landing table for my data called XMLImport, and a products table called ActiveProducts. When there are changes to a product in the XMLImport table I need it to update the ActiveProducts ...
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94 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, ...
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62 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, ...
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1answer
64 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', ...
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70 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 ...
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1answer
79 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 ...
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0answers
56 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 ...
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1answer
237 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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0answers
16 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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1answer
40 views

Procedure to read from crontab like table and populate another one periodically

Postgres 9.3 Debian 7 I'm working on a mobile game project (poker like) where an admin user can register a recurrent tournament. As it's recurrent, I modeled it crontab like as follows. ...
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1answer
58 views

Query or a New Column for Performance

I have below tables: ProductsTable (has product details), UsersTable (has all application users), RatingCategry (category for which user can rate a products like Quality, Cost etc.) and ...
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2answers
133 views

Should I stop an awfully inefficient MySQL DELETE statement?

I'm running the following statement on MySQL 5.5 in a 1GB 1CPU SSD virtual machine from Linode: DELETE table FROM ( SELECT MAX(id) id, field FROM table GROUP BY field ) temp_table INNER ...
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0answers
113 views

Select SQL_Calc_Found_Rows query extremely slow

I'm Wordpress 4.2.2 on an Ubuntu 14.04 LTS server, with PHP 5.9x and MariaDB 10.0.17. When clicking on a post on my site I see many slow queries that all resemble this and it ends up taking as 8 or 9 ...
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0answers
41 views

Delete using join or using sub-query?

I need to delete rows from a table based on what is present in a temporary table. For me, both of these statements work : DELETE from main_table where `id` in (select `deletable_id` from ...
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0answers
93 views

Query execution taking long time

SELECT sqltext.TEXT, req.session_id, req.status, req.command, req.cpu_time, req.total_elapsed_time FROM sys.dm_exec_requests req CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS sqltext select ...
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0answers
1k views

INSERT INTO with TABLOCK taking longer than without TABLOCK [closed]

I'm doing something like below to ensure the insert is minimally logged: insert into AnotherDatabase.dbo.HeapTable with (Tablock) ( <column fields ) select <column fields> from ...
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0answers
151 views

Foreign table not using index

I have a table on database temp_db named external_objects and an index on the field id, which is an MongoDB id (like 5458d717cd07870859000003). When I explain this select at this database, I got this ...
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0answers
196 views

How to speed up for huge tables in SQL select query?

I have the following huge tables. Table_1 with 500000 (0.5m) rows Table_8 with 20000000 (20m) rows Table_13 with 4000000 (4m) rows Table_6 with 500000 (0.5m) rows Table_15 with 200000 (0.2m) rows ...
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1answer
73 views

GROUP BY very slow when returning many rows

I have a query to aggregate data per day. When I run the query for a single day it is very fast. However, when I run the query for multiple days the time cost increases much faster than ...
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1answer
78 views

Why MySQL SELECT performance depends on table size? [closed]

I've got two identical tables with the following structure: CREATE TABLE words ( id bigint(20) NOT NULL, `text` int(11) NOT NULL, w1 int(11) NOT NULL, w2 int(11) NOT NULL, w3 int(11) NOT ...
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0answers
174 views

Most effective way to manage a growing list of time series data in an MS Access database

I am building a database to store time series data along with some other summary statistics. Since this is a local application I do not have access to more robust database solutions and am confined to ...
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0answers
63 views

PostgreSQL DB freezes with large inserts

I am developing a web application with an SQLAlchemy ORM linked with PostgreSQL database backend. I have this usecase where a client uploads a file of about 20 MB containing large data. What I am ...
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0answers
108 views

Query Performance - Why is a query slower when there are two criteria on the same column?

I have these two queries against a view, where I've added WHERE clauses against a date column (Indexed, Unique, Non-Clustered, Ascending): SELECT ColA FROM MyView a WHERE a.[Date] >= ...
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1answer
442 views

MongoDB document size for collection - impact on RAM and query performance

I have been advised on stackoverflow to ask this question on dba.stackexchange instead - We are using MongoDB version 3.0 with WiredTiger storage. As newbies to MongoDB, we may have designed our ...
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0answers
58 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
95 views

placing conditions in a join query join on vs where

Is there and advantage to one of the following options over the other or are they the same ? select * from T1 Join T2 on T2.id=T1.t2_id and T2.field=value; vs. select * from T1 Join T2 ...
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0answers
67 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 ...
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0answers
208 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). ...
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31 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 ...
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1answer
126 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 ...
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1answer
117 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 ...
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0answers
134 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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0answers
33 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 ...
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0answers
55 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 ...
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1answer
412 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 ...
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0answers
50 views

Is there any way to improve this code?

SELECT tblstud.studid, tblsched.ip FROM tblstud LEFT JOIN tblstudsched ON (tblstud.studid=tblstudsched.studid) LEFT JOIN tblsched ON (tblstudsched.schedid=tblsched.schedid) ...
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0answers
57 views

Can MySQL Index Merge an Composite index with a single column index?

I am tuning a query and currently have an index as following : Index 1 : (col1, col2) An example query would be : SELECT * FROM t1 WHERE col1 = '1' AND col3 = '2'; I have created an index on ...
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0answers
45 views

Best ratio for files and file groups for a highly partitioned table

I have a number of tables with exactly 1000 partitions. Each table can be up to 200G with 100M rows and cannot be compressed. Data in partitions distributed quite equally. The SQL Server has 8 ...
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1answer
139 views

Optimizing intersect query in MySQL

I'm facing a performances problem in our MariaDB server. We have a table linking users to pages, a user belongs to 1+ pages. I have a page that have users and I want to get the 10 best pages based ...
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1answer
46 views

Create a log file for check which time import has been done and to split the import files

How to create a log table for when does the last import has been done and also for Query for split the records in to 1000 while importing. to avoid the bulk insert For example : If the data ...
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1answer
75 views

Skewed Clustered Index

I have a SQL Server database that has a pretty important table (join wise) that contains just over 2.1 million rows. For the VARCHAR column that defines the clustered index, 17.5k rows contain unique ...
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1answer
73 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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0answers
196 views

Performance tuning self-joining MySQL query

I asked a question recently on the correct way to update a table using multiple joins to itself in order to generate the desired values. Updating MySQL innodb table based on multiple joins After ...