distribute by sort by /cluster by clear cut idea
up vote
0
down vote
favorite
I'm not getting a clear cut idea about distribute by sort by /cluster by in hive
according to my understanding ,multiple reducers are used when we use distribute by sort by /cluster by in hive, so that sorting happens faster
but why is that the reducers are needed in sorting of columns ,sorting can be done by a map and it does not involve any aggregate function
does it have any relation with clustered by sorted by that we use when we create a table
the problem I'm facing is,
select * from order_items cluster by order_item_order_id limit 10;
for the above query ,reducer count is not changed even though i use the command,
set mapreduce.job.reduce=4
it still remains 1
you can see here ,even though your change reducer count ,it still remains 1
though there is a post related to this , the answer given there does not clear my doubts..
thanks in advance....
hive bigdata hiveql
asked Nov 21 at 7:21
Hariharan Palanichamy
34
add a comment |
up vote
0
down vote
favorite
I'm not getting a clear cut idea about distribute by sort by /cluster by in hive
according to my understanding ,multiple reducers are used when we use distribute by sort by /cluster by in hive, so that sorting happens faster
but why is that the reducers are needed in sorting of columns ,sorting can be done by a map and it does not involve any aggregate function
does it have any relation with clustered by sorted by that we use when we create a table
the problem I'm facing is,
select * from order_items cluster by order_item_order_id limit 10;
for the above query ,reducer count is not changed even though i use the command,
set mapreduce.job.reduce=4
it still remains 1
you can see here ,even though your change reducer count ,it still remains 1
though there is a post related to this , the answer given there does not clear my doubts..
thanks in advance....
hive bigdata hiveql
asked Nov 21 at 7:21
Hariharan Palanichamy
34
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 at 7:38
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I'm not getting a clear cut idea about distribute by sort by /cluster by in hive
according to my understanding ,multiple reducers are used when we use distribute by sort by /cluster by in hive, so that sorting happens faster
but why is that the reducers are needed in sorting of columns ,sorting can be done by a map and it does not involve any aggregate function
does it have any relation with clustered by sorted by that we use when we create a table
the problem I'm facing is,
select * from order_items cluster by order_item_order_id limit 10;
for the above query ,reducer count is not changed even though i use the command,
set mapreduce.job.reduce=4
it still remains 1
you can see here ,even though your change reducer count ,it still remains 1
though there is a post related to this , the answer given there does not clear my doubts..
thanks in advance....
hive bigdata hiveql
asked Nov 21 at 7:21
Hariharan Palanichamy
34
I'm not getting a clear cut idea about distribute by sort by /cluster by in hive
according to my understanding ,multiple reducers are used when we use distribute by sort by /cluster by in hive, so that sorting happens faster
but why is that the reducers are needed in sorting of columns ,sorting can be done by a map and it does not involve any aggregate function
does it have any relation with clustered by sorted by that we use when we create a table
the problem I'm facing is,
select * from order_items cluster by order_item_order_id limit 10;
for the above query ,reducer count is not changed even though i use the command,
set mapreduce.job.reduce=4
it still remains 1
you can see here ,even though your change reducer count ,it still remains 1
though there is a post related to this , the answer given there does not clear my doubts..
thanks in advance....
hive bigdata hiveql
hive bigdata hiveql
asked Nov 21 at 7:21
Hariharan Palanichamy
34
asked Nov 21 at 7:21
Hariharan Palanichamy
34
asked Nov 21 at 7:21
Hariharan Palanichamy
34
asked Nov 21 at 7:21
Hariharan Palanichamy
34
asked Nov 21 at 7:21
Hariharan Palanichamy
34
34
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 at 7:38
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23
add a comment |
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 at 7:38
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23
Distribute by already implies using reducers. cluster by = distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 at 7:38
Distribute by already implies using reducers. cluster by = distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 at 7:38
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23
add a comment |
active
oldest
votes
active
oldest
votes
active
oldest
votes
active
oldest
votes
active
oldest
votes
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53407051%2fdistribute-by-sort-by-cluster-by-clear-cut-idea%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 at 7:38
I didn't get you , can you please elaborate, "map" does the action of filtering and sorting ,so why we need reducer here.. in the given link "youtube.com/watch?v=6r2jNcisRLw" they've used mapreduce.job.reduce to increase the reducer count.can u point me where i'm going wrong..
– Hariharan Palanichamy
Nov 21 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 at 8:23