I've got the following, slow performing, SQL query:
SELECT *
FROM news_events
WHERE 1 AND (user_id = 2416) OR id IN(SELECT content_id FROM likes WHERE user_id = 2416)
ORDER BY id DESC
LIMIT 0,10
The news_events table has indexes on user_id. And the likes table has an index on user_id.
To try to improve performance I have re-written the query using an INNER JOIN the following way:
SELECT a.*
FROM news_events a
INNER JOIN likes b ON (a.id = b.content_id)
WHERE (a.user_id = 2416) OR (b.user_id = 2416)
ORDER BY a.id DESC
LIMIT 0,10
But performance doesn't improve either. I've run explain on this last query and this is the result:
I appreciate any pointer on what I could do to improve the performance of this query.
SELECT *
FROM
(
SELECT a.*
FROM news_events a
WHERE a.user_id = 2416
UNION
SELECT ne.*
FROM news_events ne
INNER JOIN likes l
ON ne.id=l.contentid
WHERE l.user_id = 2416
)
ORDER BY 1 DESC
LIMIT 0,10
Try this query -
SELECT * FROM news_events ne
LEFT JOIN (SELECT content_id FROM likes WHERE user_id = 2416) l
ON ne.user_id = 2416 OR ne.id = l.content_id
ORDER BY
ne.id DESC
LIMIT
0, 10
These columns should be indexed: news_events.user_id, news_events.id, likes.user_id, likes.content_id.
Your query is quite good enough. Posted queries by mates are also fine. But, if you are having large set of data and you did not rebuild indexes since long then, you need to rebuild indexes on both tables.
It is a standard protocol that db admin need to rebuild all the indexes timely as well as recompile all the objects+packages in the db.
I hope it will help :)
Keep querying!
Related
I have a performance issue with the query below on MYSQL. The below query has 5 tables involved. When I apply the order by and limit, the results are retrieved in 0.3 secs. But without the order by and limit, I was able to get the results in 0.01 secs. I am tired changing the query but that did not work. Could someone please help me with this query so I can get the results in desired time (<0.3 secs).
Below are the details.
m_todos = 286579 (records)
m_pat = 214858 (records)
users = 119 (records)
m_programs = 26 (records)
role = 4 (records)
SELECT *
FROM (
SELECT t.*,
mp.name as A_name,
u.first_name, u.last_name,
p.first, p.last, p.zone, p.language,p.handling,
r.name,
u2.first_name AS created_first_name,
u2.last_name AS created_last_name
FROM m_todos t
INNER JOIN role r ON t.role_id=r.id
INNER JOIN m_pat p ON t.patient_id = p.id
LEFT JOIN users u2 ON t.created_id=u2.id
LEFT JOIN m_programs mp ON t.prog_id=mp.id
LEFT JOIN users u ON t.user_id=u.id
WHERE t.role_id !='9'
AND t.completed = '0000-00-00 00:00:00'
) C
ORDER BY priority DESC, due ASC
LIMIT 0,10
Get rid of the outer SELECT; move the ORDER BY and LIMIT in.
Indexes:
t: (completed)
t: (priority, due)
I assume priority and due are in t?? Please be explicit in the query. It could make a huge difference.
If the following works, it should speed things up a lot: Start by finding the t.id without all the JOINs:
SELECT id
FROM m_todos
WHERE role_id !='9'
AND completed = '0000-00-00 00:00:00'
ORDER BY priority DESC, due DESC
LIMIT 10
That will benefit from this covering composite index:
INDEX(completed, role_id, priority, due, id)
Debug that. Then use it in the rest:
SELECT t.*, the-other-stuff
FROM ( that-query ) AS t1
JOIN m_todos AS t USING(id)
then-the-rest-of-the-JOINs
ORDER BY priority DESC, due ASC -- yes, again
If you don't need all of t.*, it may be beneficial to spell out the actual columns needed.
The reason for this to run much faster is that the 10 rows are found efficiently by looking only at the one table. The original code was shoveling around a lot more rows than 10 and they included all the columns of t, plus columns from the other tables.
My version does only 10 lookups for all the extra stuff.
I'm struggling to make a query efficient enough. I'm using Doctrine2 ORM (the query is build with QueryBuilder) and part of my query is running very slow - takes about 4s with table of 5000 rows.
This is the relevant part of db schema:
TABLE user
id (primary)
... (plenty of rows, not relevant to the query)
TABLE slot
id (primary)
user_id (foreign for user)
date (datetime)
And this is how my query looks like (it's the basic version, there's a lot of filters to be applied, but these work like fine for now)
SELECT
u.id AS uid,
COUNT(DISTINCT s_order.id) AS sclr_1,
COUNT(DISTINCT s_filter.id) AS sclr_2
FROM
user u
LEFT JOIN slot s_order ON (s_order.user_id = u.id)
LEFT JOIN slot s_filter ON (s_filter.user_id = u.id)
WHERE
(
(
(
s_order.date BETWEEN ?
AND ?
)
AND (
s_filter.date BETWEEN ?
AND ?
)
)
AND (u.deleted_at IS NULL)
)
AND u.userType IN ('2')
GROUP BY
u.id
HAVING
sclr_2 > 0
ORDER BY
sclr_1 DESC
LIMIT
12
Let me explain what I'm trying to achieve here:
I need to filter users who has any slots between 1 week ago and 1 week ahead, then order them by count of slots available between now and 1 week ahead. The part of query causing issues is LEFT JOIN of s_filter and I'm wondering whether perhaps there's a way to improve the performance of that query?
Any help appreciated really, even if it's only plain SQL I'll try to convert it to DQL myself!
#UPDATE
Just an additional info that I forgot, the LIMIT in query is for pagination purposes!
#UPDATE 2
After a while of tweaking the query I figured out that I can use JOIN for filtering instead of LEFT JOIN + COUNT, so my query does look like that now:
SELECT
u.id AS uid, COUNT(DISTINCT s_order.id) AS ordinal
FROM
langu_user u
LEFT JOIN
slot s_order ON (s_order.user_id = u.id) AND s_order.date BETWEEN '2017-02-03 14:03:22' AND '2017-02-10 14:03:22'
JOIN
slot s_filter ON (s_filter.user_id = u.id) AND s_filter.date BETWEEN '2017-01-27 14:03:22' AND '2017-02-10 14:03:22'
WHERE
u.deleted_at IS NULL
AND u.userType IN ('2')
GROUP BY u.id
ORDER BY ordinal DESC
LIMIT 12
And it went down from 4.1-4.3s to 3.6~
My MySQL query is loading very slow (over 30 secs), I was wondering what tweaks I can make to optimize it.
The query should return the last post with the string "?" of all threads.
SELECT FeedbackId, ParentFeedbackId, PageId, FeedbackTitle, FeedbackText, FeedbackDate
FROM ReaderFeedback AS c
LEFT JOIN (
SELECT max(FeedbackId) AS MaxFeedbackId
FROM ReaderFeedback
WHERE ParentFeedbackId IS NOT NULL
GROUP BY ParentFeedbackId
) AS d ON d.MaxFeedbackId = c.FeedbackId
WHERE ParentFeedbackId IS NOT NULL
AND FeedbackText LIKE '%?%'
GROUP BY ParentFeedbackId
ORDER BY d.MaxFeedbackId DESC LIMIT 50
Before discuss this problem, I have formatted your SQL:
SELECT feedbackid,
parentfeedbackid,
pageid,
feedbacktitle,
feedbacktext,
feedbackdate
FROM readerfeedback AS c
LEFT JOIN (SELECT Max(feedbackid) AS MaxFeedbackId
FROM readerfeedback
WHERE parentfeedbackid IS NOT NULL
GROUP BY parentfeedbackid) AS d
ON d.maxfeedbackid = c.feedbackid
WHERE parentfeedbackid IS NOT NULL
AND feedbacktext LIKE '%?%'
GROUP BY parentfeedbackid
ORDER BY d.maxfeedbackid DESC
LIMIT 50
Since there is an Inefficient query criteria in your SQL:
feedbacktext LIKE '%?%'
Which is not able to take benefit from Index and needs a full scan, I suggest you to add a new field
isQuestion BOOLEAN
to your table, and then add logic in your program to assign this field when insert/update a feedbacktext.
Finally your can query based on this field and take benefit from index.
Firstly your SQL is not valid. The outer Group by is not valid.
According to the SQL the second group by is not needed. I moved the 2 where into inner SQL, as well as the limit, wonder if the following is quicker:
SELECT FeedbackId, ParentFeedbackId, PageId, FeedbackTitle, FeedbackText, FeedbackDate
FROM ReaderFeedback AS c
JOIN (
SELECT max(FeedbackId) AS MaxFeedbackId
FROM ReaderFeedback
WHERE ParentFeedbackId IS NOT NULL
AND FeedbackText LIKE '%?%'
GROUP BY ParentFeedbackId
ORDER BY 1 DESC LIMIT 50
) AS d ON d.MaxFeedbackId = c.FeedbackId
Please have a look at your table structure, see if there is any normalisation be downed for speed concern.
The below query is very slow (takes around 1 second), but is only searching approx 2500 records (+ inner joined tables).
if i remove the ORDER BY, the query runs in much less time (0.05 or less)
OR if i remove the part nested select below "# used to select where no ProfilePhoto specified" it also runs fast, but i need both of these included.
I have indexes (or primary key) on :tPhoto_PhotoID, PhotoID, p.Enabled, CustomerID, tCustomer_CustomerID, ProfilePhoto (bool), u.UserName, e.PrivateEmail, m.tUser_UserID, Enabled, Active, m.tMemberStatuses_MemberStatusID, e.tCustomerMembership_MembershipID, e.DateCreated
(do i have too many indexes? my understanding is add them anywhere i use WHERE or ON)
The Query :
SELECT e.CustomerID,
e.CustomerName,
e.Location,
SUBSTRING_INDEX(e.CustomerProfile,' ', 25) AS Description,
IFNULL(p.PhotoURL, PhotoTable.PhotoURL) AS PhotoURL
FROM tCustomer e
LEFT JOIN (tCustomerPhoto ep INNER JOIN tPhoto p ON (ep.tPhoto_PhotoID = p.PhotoID AND p.Enabled=1))
ON e.CustomerID = ep.tCustomer_CustomerID AND ep.ProfilePhoto = 1
# used to select where no ProfilePhoto specified
LEFT JOIN ((SELECT pp.PhotoURL, epp.tCustomer_CustomerID
FROM tPhoto pp
LEFT JOIN tCustomerPhoto epp ON epp.tPhoto_PhotoID = pp.PhotoID
GROUP BY epp.tCustomer_CustomerID) AS PhotoTable) ON e.CustomerID = PhotoTable.tCustomer_CustomerID
INNER JOIN tUser u ON u.UserName = e.PrivateEmail
INNER JOIN tmembers m ON m.tUser_UserID = u.UserID
WHERE e.Enabled=1
AND e.Active=1
AND m.tMemberStatuses_MemberStatusID = 2
AND e.tCustomerMembership_MembershipID != 6
ORDER BY e.DateCreated DESC
LIMIT 12
i have similar queries that but they run much faster.
any opinions would be grateful:
Until we get more clarity on your question between working in other query etc..Try EXPLAIN {YourSelectQuery} in MySQL client and see the suggestions to improve the performance.
Please help me optimize query about getting reccomended (rec) for movies. I have many records and query run quite slow. The following query run for 2 mins
SELECT rec.toMovieID, sum(rec.score)
FROM rec
WHERE movieID in
(SELECT movieid as movieID FROM userFavorites as ufv WHERE ufv.userid = 29)
GROUP BY rec.toAMovieID
ORDER BY rec.score DESC
LIMIT 10
Do you think I can optimize it more?
You can use an inner join instead of a subselect
SELECT
rec.toMovieID,
sum(rec.score)
FROM rec INNER JOIN userFavorites ON rec.movieID = userFavorites.movieid
WHERE
userid = 29
GROUP BY rec.toAMovieID
ORDER BY rec.score DESC
LIMIT 10
You should set indexes on rows in where clause, at least for movieid and userid. (If not allready done)
You can use exists:
SELECT rec.toMovieID, sum(rec.score)
FROM rec r
WHERE EXISTS (SELECT 1 FROM userFavorites as ufv WHERE ufv.userid = 29 and ufv.MovieId = r.MovieId)
GROUP BY rec.toAMovieID
ORDER BY rec.score DESC
LIMIT 10;
You have to be careful using a join because of duplicate records.