distribute by sort by /cluster by clear cut idea
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
add a comment |
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
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 '18 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..
– user5003155
Nov 21 '18 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23
add a comment |
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
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 '18 at 7:21
user5003155
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 '18 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..
– user5003155
Nov 21 '18 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23
add a comment |
Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.
– leftjoin
Nov 21 '18 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..
– user5003155
Nov 21 '18 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23
Distribute by already implies using reducers. cluster by = distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 '18 at 7:38
Distribute by already implies using reducers. cluster by = distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 '18 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..
– user5003155
Nov 21 '18 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..
– user5003155
Nov 21 '18 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23
add a comment |
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Distribute byalready implies using reducers.cluster by= distribute + sort. 'mapred.reduce.tasks' is correct property.– leftjoin
Nov 21 '18 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..
– user5003155
Nov 21 '18 at 7:49
he used mapreduce.job.reduces, you mapreduce.job.reduce
– leftjoin
Nov 21 '18 at 8:23