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2
votes
1answer
139 views

Mysql join table order by index

First Master Table CREATE TABLE `edipostingmaster` ( `ID` bigint(20) NOT NULL AUTO_INCREMENT, `applied` int(11) DEFAULT '0', `fileName` varchar(255) DEFAULT NULL, `checkNo` varchar(100) ...
1
vote
1answer
22 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 ...
0
votes
1answer
20 views

Disc IO for query in MongoDB

is there a way to tell how much data MongoDB is reading from disc and how much from cache for a query ? I looked at the explain()-Function but did not find this kind of informations. Thanks, Andre
0
votes
1answer
152 views

Help interpreting a MySQL execution plan

I'm trying to understand a slow query. The SELECT has been running (at this moment) for almost 18000 seconds (output from a SELECT on PROCESSLIST): id: 22 time: 17870 ...
2
votes
0answers
122 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
0answers
129 views

Almost identical queries but large time difference in execution

Exhibit A SELECT SUM(value) FROM Credits RIGHT JOIN calendar ON datefield = DATE(FROM_UNIXTIME(created_at)) WHERE confirm = 1 && reason = 1 && country = 'it' && created_at ...
1
vote
0answers
41 views

Explain partitions

What does the possible keys, reference and rows indicate in explain partitions? I have used partitions on the table and I executing the explain partitions with a query: select ...
1
vote
0answers
71 views

Amazon Redshift: “*SELECT* 1” vs. volt_dt_0 vs. volt_tt_51343b6aa3bd4

I've noticed subqueries in Amazon Redshift can be represented in the explain plan in 3 separate ways: -> XN Subquery Scan "*SELECT* 1" -> XN Subquery Scan volt_dt_0 -> XN Seq Scan on ...
1
vote
0answers
84 views

Mysql: Large Query with subqueries optimization

Any query optimization gurus in the house?? Anyway, I am trying to attack this on two fronts, one being to code a way around it but secondly, I'm thinking some real optimization might help in the ...
0
votes
0answers
63 views

Optimizing query - understanding explain

I've got a query (partly generated by django orm, but can be modified). For some reason, It's very slow (between 1.5 -3 seconds, without having lots of data on the system) . I've got an "explain" ...
0
votes
0answers
81 views

explain plan ,joins and optimization

I have to join 6 tables in sql query and each of these tables have 1 join to each of there master tables . Hence i have defined 5 subqueries within a sql query but i am seeing a lot of performance ...
0
votes
0answers
39 views

Large-query optimization: given my “explain” results, what stands out?

I've got a monster query, which runs quite quick in many cases, but in some cases very much slower. The EXPLAIN output below is from one of the slow cases. I'm guessing that the slowdown is related ...