MySQL GROUP BY query drastically slow down when after data reaches a certain amount
I need help finding out why the following query that aggregates peoples' responses by "item" slows down considerably after the data being aggregated reaches a certain size.
select
t1.item,
count(t1.val) as count,
round(avg(t1.resp), 2) as mean,
round(std(t1.resp), 2) as std
from
person_response as t1
join person_info as t2
on t1.person_id = t2.id
where
t1.resp between 1 and 5
and t2.is_valid = 1
and (t2.attr1, t2.attr2) in ((?, ?), ...)
and t2.attr3 in (?, ...)
and t1.item in (?, ...)
group by t1.item
;
t1 has about 15 million rows and t2 has about 200,000 rows. All columns involved in the query are indexed. If the WHERE clause captures under 50,000 rows, execution is generally under 100 ms. If the WHERE clause captures 138,665 rows, execution is under 500 ms. But when I extend the WHERE clause to capture 150,685 rows, execution takes considerably longer at 3 m 40 s 366 ms. Nearly 4 minutes!
mysql
asked 12 mins ago
stackerstacker
2425
add a comment |
I need help finding out why the following query that aggregates peoples' responses by "item" slows down considerably after the data being aggregated reaches a certain size.
select
t1.item,
count(t1.val) as count,
round(avg(t1.resp), 2) as mean,
round(std(t1.resp), 2) as std
from
person_response as t1
join person_info as t2
on t1.person_id = t2.id
where
t1.resp between 1 and 5
and t2.is_valid = 1
and (t2.attr1, t2.attr2) in ((?, ?), ...)
and t2.attr3 in (?, ...)
and t1.item in (?, ...)
group by t1.item
;
t1 has about 15 million rows and t2 has about 200,000 rows. All columns involved in the query are indexed. If the WHERE clause captures under 50,000 rows, execution is generally under 100 ms. If the WHERE clause captures 138,665 rows, execution is under 500 ms. But when I extend the WHERE clause to capture 150,685 rows, execution takes considerably longer at 3 m 40 s 366 ms. Nearly 4 minutes!
mysql
asked 12 mins ago
stackerstacker
2425
Please provideSHOW CREATE TABLE t1andSHOW CREATE TABLE t2outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.
– Willem Renzema
7 mins ago
add a comment |
I need help finding out why the following query that aggregates peoples' responses by "item" slows down considerably after the data being aggregated reaches a certain size.
select
t1.item,
count(t1.val) as count,
round(avg(t1.resp), 2) as mean,
round(std(t1.resp), 2) as std
from
person_response as t1
join person_info as t2
on t1.person_id = t2.id
where
t1.resp between 1 and 5
and t2.is_valid = 1
and (t2.attr1, t2.attr2) in ((?, ?), ...)
and t2.attr3 in (?, ...)
and t1.item in (?, ...)
group by t1.item
;
t1 has about 15 million rows and t2 has about 200,000 rows. All columns involved in the query are indexed. If the WHERE clause captures under 50,000 rows, execution is generally under 100 ms. If the WHERE clause captures 138,665 rows, execution is under 500 ms. But when I extend the WHERE clause to capture 150,685 rows, execution takes considerably longer at 3 m 40 s 366 ms. Nearly 4 minutes!
mysql
asked 12 mins ago
stackerstacker
2425
I need help finding out why the following query that aggregates peoples' responses by "item" slows down considerably after the data being aggregated reaches a certain size.
select
t1.item,
count(t1.val) as count,
round(avg(t1.resp), 2) as mean,
round(std(t1.resp), 2) as std
from
person_response as t1
join person_info as t2
on t1.person_id = t2.id
where
t1.resp between 1 and 5
and t2.is_valid = 1
and (t2.attr1, t2.attr2) in ((?, ?), ...)
and t2.attr3 in (?, ...)
and t1.item in (?, ...)
group by t1.item
;
t1 has about 15 million rows and t2 has about 200,000 rows. All columns involved in the query are indexed. If the WHERE clause captures under 50,000 rows, execution is generally under 100 ms. If the WHERE clause captures 138,665 rows, execution is under 500 ms. But when I extend the WHERE clause to capture 150,685 rows, execution takes considerably longer at 3 m 40 s 366 ms. Nearly 4 minutes!
mysql
mysql
asked 12 mins ago
stackerstacker
2425
asked 12 mins ago
stackerstacker
2425
asked 12 mins ago
stackerstacker
2425
asked 12 mins ago
stackerstacker
2425
asked 12 mins ago
stackerstacker
2425
2425
Please provideSHOW CREATE TABLE t1andSHOW CREATE TABLE t2outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.
– Willem Renzema
7 mins ago
add a comment |
Please provideSHOW CREATE TABLE t1andSHOW CREATE TABLE t2outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.
– Willem Renzema
7 mins ago
Please provide
SHOW CREATE TABLE t1 and SHOW CREATE TABLE t2 outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.– Willem Renzema
7 mins ago
Please provide
SHOW CREATE TABLE t1 and SHOW CREATE TABLE t2 outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.– Willem Renzema
7 mins ago
add a comment |
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Please provide
SHOW CREATE TABLE t1andSHOW CREATE TABLE t2outputs. "All columns involved in the query are indexed." That statement doesn't mean much if they are just single column indexes.– Willem Renzema
7 mins ago