A class of issues where a database executes a query inefficiently due to the optimiser selecting an innapropriate query plan.

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7 views

Improving performance of a weighted search query in SQLite3

For an intra-site search I have this table in an SQLite3 database, that relates ids to search terms with a certain weight: CREATE TABLE search_index ( id INTEGER(7) REFERENCES other_table, ...
-7
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0answers
32 views

Vendor query yields poor performance [on hold]

I have a query that the vendor will not change. The query takes 4 hours and of course slows down the entire application. Has anyone run into this? Query Code Here
1
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1answer
61 views

Why SELECT is so slow

I have the following table 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 NULL, w4 int(11) NOT NULL, ...
2
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1answer
61 views

Slow PostgreSQL query

I'm building a search interface for a web site that currently searches through approximately 2 million pieces of real estate with approximately 60 million attributes (address, city, state, ZIP, beds, ...
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2answers
22 views

Awful execution plans after migrating from MySQL 5.5.11 to MariaDB 5.5.41

We just migrated our web site database from a server running MySQL 5.5.11 to one running MariaDB 5.5.41. Everything is working mostly fine, except there's at least one query from our storefront that's ...
1
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1answer
75 views

high PAGEIOLATCH_SH waits on server [closed]

EDIT: I know this question is closed, but I hope it will help someone. The problem is on our disks ( cluster ). Using PerfMon, I could create some counters ( disk reads and writes ) and the reads ...
1
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0answers
25 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 ...
4
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2answers
66 views
+50

Convert date in date list condition to list of date ranges

I want to look for all the records that occur on specific dates. SELECT * FROM table1 WHERE date(column) in ($date1, $date2, ...); However, as many of you, know this kind of comparison doesn't get ...
2
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0answers
63 views

Why is this MySQL query “using where” instead of “using index”?

Could you help me with this query, please? SELECT p.patid, MAX(c1.eventdate) as eventdate from patient as p left join op_adv_effects._clinical as c1 on p.patid = c1.patid left join ...
2
votes
1answer
81 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 ...
2
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1answer
56 views

DB2 CASE statement faster with parentheses around entire WHEN

Trying to optimize slow queries, someone on my team come across this. Having this in our stored proc: CASE WHEN MYCOL BETWEEN @STARTNUM AND @ENDNUM AND RECTYPE = 'RO' THEN 1 ELSE 0 ...
1
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0answers
23 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 ...
2
votes
2answers
48 views

MySQL taking too much CPU

Below is my .cnf file and if I see my CPU consumption 99.99% of it my the mysqld commands. The MySQL server is connected from remote machines that update data in it frequently, but I make sure that ...
1
vote
1answer
75 views

Index to filter a view before joining the underlying tables [closed]

Using SQL Server 2008 R2 Suppose you have a query like the following select top 1 * from view_cms_user where UserId = 1234 or UserPasswordRequestHash = 'anxazno121o3n' view_cms_user is basically: ...
0
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0answers
5 views

Create table with select Query on DB link

I'm trying to execute the following query, it is taking more than usual time. I'm retrieving data from db link. without the create table statement the query is giving results. for Create table also if ...
0
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2answers
80 views

How can I replace the following query with ISNULL function in SQL?

I have the following query. For performance optimization reasons I have been asked to replace the logic with ISNULL function in SQL. How can I achieve this? please advice. SELECT ...
0
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0answers
54 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] >= ...
0
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1answer
18 views

MySQL 2 Million Rows, longtext and varchar indexes

I'm trying to find a solution for this, with no success. I have a table with ~2M rows, and I need to do a WHERE with 3 expressions using OR. name LIKE '%PARAM%' OR text1 LIKE '%PARAM%' OR text2 LIKE ...
0
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2answers
38 views

SQL Server 2005 query with multiple conditions, some indexed, some not

I have a table with 50 million rows. It is indexed on zip. A query Select * from table where zip = '12345' returns 20,000 rows in about 2 seconds When I add an additional condition it jumps to ...
1
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2answers
32 views

Two (almost) identical queries, but only one of them uses the index

I have a table with two columns, batch_id and study_id. There are indexes on both columns. I want to get a random row back from MySQL. I originally wrote: SELECT * FROM alt_join_batch_study ORDER BY ...
0
votes
1answer
31 views

Optimizing a query on Mysql 5.5.24

I am trying to optimize the query SELECT CONCAT(lastname, ', ', title, ' ', firstname) AS fullName, e.lastname, e.firstname, e.email, e.userType, e.userID FROM employee e, ...
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3answers
40 views

How work SELECT in database [closed]

My table has 8,400 rows of user information. Say I submit the query SELECT name FROM users WHERE name = 'jhon'; I know that 'jhon' is the 400th row in my dataset. My question is, will the DBMS ...
1
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1answer
40 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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2answers
89 views

Why is “select join insert” so much faster than “loop insert”?

MySQL docs state that the time required for inserts has these approximate proportions: Connecting: (3) Sending query to server: (2) Parsing query: (2) Inserting row: (1 × size of row) ...
0
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0answers
41 views

Which of sys.dm_exec_query_stats columns should I pay most attention?

I'm trying to tune my database and currently staring into sys.dm_exec_query_stats (with actual queries): SELECT SqlText.text, * from sys.dm_exec_query_stats CROSS APPLY ...
6
votes
2answers
296 views

Unexpected Implicit conversion in a procedure

I have a procedure like this (simplified): CREATE PROCEDURE test @userName VARCHAR(64) SELECT * FROM member M INNER JOIN order O ON M.MemberId=O.MemberId WHERE M.Username = @userName There is a ...
0
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2answers
63 views

Oracle query optimization

We have a query that runs on a view and its execution time is about 6 min. SELECT COUNT(*) FROM someschema.item_total_violations WHERE channel_id = 122507833 AND item_date >= ...
0
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1answer
16 views

represent multiple entities to one entity relationship

If suppose, I have following tables: Here, person can own either home or car. person can't own both at a time. If person owns home, then owns field will be equal to 1, if it owns car, owns field ...
0
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0answers
7 views

indexing table column on the go of mysql query commit

It is said that to optimize the query cost of execution, then it would be by indexing the field of tables in database. Since I don't have a permission to enter the phpmyadmin in my web server as I am ...
0
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0answers
21 views

Best way to run a formula (segment) a large number of users with custom attributes

Here is my question. I have a table that stores a large number of people (80 mil). Each person has a GUID id. Then I have another table (or set of tables) that stores information about people. e.g. ...
0
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1answer
75 views

Improve Query Performance

I have the following sqlite3-Tables: db.execute("""CREATE TABLE IF NOT EXISTS STATIONS (StationUID INTEGER PRIMARY KEY AUTOINCREMENT, StationNumber TEXT NOT NULL, ...
0
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0answers
53 views

Slow running Oracle query caused by unnecessary full table scan

I'm by no means an expert with Oracle, but I know enough in terms of how to analyze explain plans and perform basic optimizations. However, this time, Oracle has stumped me with it's explain plan. ...
6
votes
2answers
148 views

Hindrance in TSQL SVF Call

I have a simply Products data table with 100k records (just generates some random data): set nocount on create table dbo.temp_Products ( [ProductID] int, [Type] tinyint, [Price] float, ...
0
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1answer
33 views

InnoDB Table has backed up INSERT and UPDATE queries, high CPU

I am running an MySQL DB with all InnoDB tables. I often have many queries backed up for the same table when I run SHOW PROCESSLIST; Basically, I keep a table of every logged in customer and update ...
0
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0answers
51 views

Optimising an SP - Left Join against several big tables

I have stumbled upon performance bottleneck due to LEFT JOIN against several big tables (approx. 6 million rows of data, consisting of 10 columns). Any suggestions on how to optimize this SP is ...
0
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0answers
34 views

How to divide a big SQL Query into small query

I am trying to traverse the whole file system. I am picking each and every file and then trying to insert it into the SQLite Database. Before inserting I am also calculating the checksum of each file. ...
0
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1answer
45 views

Viewing execution plans for queries with parameters

I have a sample query generated by an application (Microsoft Dynamics AX 2012 in this case) which is ineffective performance-wise (cross joins, order by etc.) I would like to display its execution ...
0
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0answers
34 views

Mysql cursor alternative / Optimization - each row updates are too slow

I'm looking to optimize my cursor based update or actually replacing it... Situation We're carrying out promotional campaigns and I'd like to track user activity per campaign. Logic Each campaign ...
0
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0answers
32 views

delete query performance issue on mysql

I have two tables table1, table2 where table2 is a subset of table1 (basically created with the query create table table2 as select * from table1 where .....) Now, I am trying to run the below query. ...
0
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1answer
20 views

Optimize Query in MySQL

I've following tables with respective fields 1) wi_individual_g(ind_id,ind_is_recepient,ind_deleted,ind_district_id,...) - Around 200K data 2) wi_individual_p(ind_id,prg_id,...) Around 250K data 3) ...
1
vote
1answer
38 views

SQL Server execution plan using a view, but no view is inside the stored procedure

I am troubleshooting this slow stored procedure and when checking the actual execution plan I noticed a warning of a possible missing index. Taking a closer look, it's against one of the views, not an ...
1
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0answers
53 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 ...
0
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0answers
20 views

DB space vs query complexity tradeoff

I have a dilemma - Right now I have a query that I do constantly - joining 5 tables on different columns, calculate stuff per row, distinct on that, and do that with offset and limit (pagination). I ...
1
vote
1answer
28 views

Postgres - Insert performance with indexes

We have a table with about 20 columns in a Postgres 9.2.10 DB. For better performance on some SELECT queries, we plan to add an index on one column with data type timestamp. As the index also can slow ...
0
votes
1answer
23 views

Clustering a heap by date in stead of unique composite key

I've been working on improving the performance of a large reporting database. This database is 2TB in size, and one of the larger tables is a heap with three non-clustered indexes on it. The ...
0
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0answers
32 views

trying to a lag a column in SQLite

Sorry if this is too basic for this forum, but I have had no luck in StackOverflow. I am a newbie to SQL. I am using SQLite. I have a table where rows represent individuals in a point in time. I am ...
2
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0answers
44 views

Performance differs on same query against two (almost) identical tables?

I'm running these two queries in SQL Server 2012: SELECT tpua.Field1, CAST(round(twg.Field2 * 2, 0) / 2 As Decimal(8,1)) As Field2, CAST((round((twg.Field3/10.0) * 2, 0) / 2) * 10 As int) As ...
1
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2answers
184 views

Is it a good idea to include a value column (e.g. from measurements) in an index?

Is it a good idea to include a value column into an index for a table which has many million rows? For example a measurement table which looks kind of like this: CREATE TABLE measurements ( id ...
0
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1answer
60 views

Complex query performance in MySQL InnoDB versus MyISAM

I am running on MariaDB 10.0.15 on a 4GB RAM cloud server with Local SSD disk for database. My model: users <n---n> right_holders <n---n> tracks ---n> raw_detections I have this ...
0
votes
1answer
24 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 ...