Re: Sort Order in HBase with Pig/Piglatin in Java
"but since hbase returns the values sorted" You are right. I just wanted to highlight the subtlety that you are essentially relying on the external mechanism for the desired feature (sorting) rather than the collection/container itself (as in TreeMap.) In this case, it is most probably redundant and you can use LinkedHashMap to avoid resorting. Regards, Shahab On Fri, Sep 13, 2013 at 12:50 PM, John wrote: > Yes, thats a good point @ Shahab, but since hbase returns the values sorted > everything shlould be fine and I can use the LinkedHashMap. > > Thanks to both of you! > > > 2013/9/13 Shahab Yunus > > > "But I used > > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > > or LinkedHashMap?" > > > > If you are asking from functionality perspective then there is a > difference > > between them that LinkedHashMap maintains the order in which items were > > entered in the map. So if they were entered in the correct order then you > > are fine but for any reason if they are not entered in the correct order > > that you want (i.e. some kind of sort order) then you will not be able to > > get your desired order. > > > > TreeMap on the other handle, makes sure that the ordering is > > right according to the natural ordering of the elements. Gives you more > > security in terms of what you want. > > > > Regards, > > Shahba > > > > > > On Fri, Sep 13, 2013 at 12:29 PM, John > wrote: > > > > > Hi, thanks for your quick answer! I figured it out by my self since the > > > mailing server was down the last 2hours?! Btw. I did option 1. But I > > used > > > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > > > or LinkedHashMap? > > > > > > Anyway thanks :) > > > > > > > > > 2013/9/13 Pradeep Gollakota > > > > > > > Thats a great observation John! The problem is that HBaseStorage maps > > > > columns families into a HashMap, so the sort ordering is completely > > lost. > > > > > > > > You have two options: > > > > > > > > 1. Modify HBaseStorage to use a SortedMap data structure (i.e. > TreeMap) > > > and > > > > use the modified HBaseStorage. (or make it configurable) > > > > 2. Since you convert the map to a bag, you can sort the bag in a > nested > > > > foreach statement. > > > > > > > > I prefer option 1 myself because it would be more performant than > > option > > > 2. > > > > > > > > > > > > On Fri, Sep 13, 2013 at 7:31 AM, John > > > wrote: > > > > > > > > > I have created a HBase Table in the hbase shell and added some > data. > > In > > > > > http://hbase.apache.org/book/dm.sort.html is written that the > > datasets > > > > are > > > > > first sorted by the rowkey and then the column. So I tried > something > > in > > > > the > > > > > HBase Shell: http://pastebin.com/gLVAX0rJ > > > > > > > > > > Everything looks fine. I got the right order a -> c -> d like > > expected. > > > > > > > > > > Now I tried the same with Apache Pig in Java: > > > > http://pastebin.com/jdTpj4Fu > > > > > > > > > > I got this result: > > > > > > > > > > (key1,[c#val,d#val,a#val]) > > > > > > > > > > So, now the order is c -> d -> a. That seems a little odd to me, > > > > shouldn't > > > > > it be the same like in HBase? It's important for me to get the > right > > > > order > > > > > because I transform the map afterwards into a bag and then join it > > with > > > > > other tables. If both inputs are sorted I could use a merge join > > > without > > > > > sorting these two datasets. So does anyone know how it is possible > to > > > get > > > > > the sorted map (or bag) of the columns? > > > > > > > > > > > > > > > thanks > > > > > > > > > > > > > > >
Re: Sort Order in HBase with Pig/Piglatin in Java
Yes, thats a good point @ Shahab, but since hbase returns the values sorted everything shlould be fine and I can use the LinkedHashMap. Thanks to both of you! 2013/9/13 Shahab Yunus > "But I used > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > or LinkedHashMap?" > > If you are asking from functionality perspective then there is a difference > between them that LinkedHashMap maintains the order in which items were > entered in the map. So if they were entered in the correct order then you > are fine but for any reason if they are not entered in the correct order > that you want (i.e. some kind of sort order) then you will not be able to > get your desired order. > > TreeMap on the other handle, makes sure that the ordering is > right according to the natural ordering of the elements. Gives you more > security in terms of what you want. > > Regards, > Shahba > > > On Fri, Sep 13, 2013 at 12:29 PM, John wrote: > > > Hi, thanks for your quick answer! I figured it out by my self since the > > mailing server was down the last 2hours?! Btw. I did option 1. But I > used > > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > > or LinkedHashMap? > > > > Anyway thanks :) > > > > > > 2013/9/13 Pradeep Gollakota > > > > > Thats a great observation John! The problem is that HBaseStorage maps > > > columns families into a HashMap, so the sort ordering is completely > lost. > > > > > > You have two options: > > > > > > 1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) > > and > > > use the modified HBaseStorage. (or make it configurable) > > > 2. Since you convert the map to a bag, you can sort the bag in a nested > > > foreach statement. > > > > > > I prefer option 1 myself because it would be more performant than > option > > 2. > > > > > > > > > On Fri, Sep 13, 2013 at 7:31 AM, John > > wrote: > > > > > > > I have created a HBase Table in the hbase shell and added some data. > In > > > > http://hbase.apache.org/book/dm.sort.html is written that the > datasets > > > are > > > > first sorted by the rowkey and then the column. So I tried something > in > > > the > > > > HBase Shell: http://pastebin.com/gLVAX0rJ > > > > > > > > Everything looks fine. I got the right order a -> c -> d like > expected. > > > > > > > > Now I tried the same with Apache Pig in Java: > > > http://pastebin.com/jdTpj4Fu > > > > > > > > I got this result: > > > > > > > > (key1,[c#val,d#val,a#val]) > > > > > > > > So, now the order is c -> d -> a. That seems a little odd to me, > > > shouldn't > > > > it be the same like in HBase? It's important for me to get the right > > > order > > > > because I transform the map afterwards into a bag and then join it > with > > > > other tables. If both inputs are sorted I could use a merge join > > without > > > > sorting these two datasets. So does anyone know how it is possible to > > get > > > > the sorted map (or bag) of the columns? > > > > > > > > > > > > thanks > > > > > > > > > >
Re: Sort Order in HBase with Pig/Piglatin in Java
"But I used a LinkedHashMap insead. Do you knows whats the better choice? TreeMap or LinkedHashMap?" If you are asking from functionality perspective then there is a difference between them that LinkedHashMap maintains the order in which items were entered in the map. So if they were entered in the correct order then you are fine but for any reason if they are not entered in the correct order that you want (i.e. some kind of sort order) then you will not be able to get your desired order. TreeMap on the other handle, makes sure that the ordering is right according to the natural ordering of the elements. Gives you more security in terms of what you want. Regards, Shahba On Fri, Sep 13, 2013 at 12:29 PM, John wrote: > Hi, thanks for your quick answer! I figured it out by my self since the > mailing server was down the last 2hours?! Btw. I did option 1. But I used > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > or LinkedHashMap? > > Anyway thanks :) > > > 2013/9/13 Pradeep Gollakota > > > Thats a great observation John! The problem is that HBaseStorage maps > > columns families into a HashMap, so the sort ordering is completely lost. > > > > You have two options: > > > > 1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) > and > > use the modified HBaseStorage. (or make it configurable) > > 2. Since you convert the map to a bag, you can sort the bag in a nested > > foreach statement. > > > > I prefer option 1 myself because it would be more performant than option > 2. > > > > > > On Fri, Sep 13, 2013 at 7:31 AM, John > wrote: > > > > > I have created a HBase Table in the hbase shell and added some data. In > > > http://hbase.apache.org/book/dm.sort.html is written that the datasets > > are > > > first sorted by the rowkey and then the column. So I tried something in > > the > > > HBase Shell: http://pastebin.com/gLVAX0rJ > > > > > > Everything looks fine. I got the right order a -> c -> d like expected. > > > > > > Now I tried the same with Apache Pig in Java: > > http://pastebin.com/jdTpj4Fu > > > > > > I got this result: > > > > > > (key1,[c#val,d#val,a#val]) > > > > > > So, now the order is c -> d -> a. That seems a little odd to me, > > shouldn't > > > it be the same like in HBase? It's important for me to get the right > > order > > > because I transform the map afterwards into a bag and then join it with > > > other tables. If both inputs are sorted I could use a merge join > without > > > sorting these two datasets. So does anyone know how it is possible to > get > > > the sorted map (or bag) of the columns? > > > > > > > > > thanks > > > > > >
Re: Sort Order in HBase with Pig/Piglatin in Java
No problem! In this case, insertion order is the same as natural order, so I think a LinkedHashMap is probably a better choice for this particular use case. Here's a great SO post about the differences between HashMap, TreeMap and LinkedHashMap. http://stackoverflow.com/questions/2889777/difference-between-hashmap-linkedhashmap-and-sortedmap-in-java On Fri, Sep 13, 2013 at 9:29 AM, John wrote: > Hi, thanks for your quick answer! I figured it out by my self since the > mailing server was down the last 2hours?! Btw. I did option 1. But I used > a LinkedHashMap insead. Do you knows whats the better choice? TreeMap > or LinkedHashMap? > > Anyway thanks :) > > > 2013/9/13 Pradeep Gollakota > > > Thats a great observation John! The problem is that HBaseStorage maps > > columns families into a HashMap, so the sort ordering is completely lost. > > > > You have two options: > > > > 1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) > and > > use the modified HBaseStorage. (or make it configurable) > > 2. Since you convert the map to a bag, you can sort the bag in a nested > > foreach statement. > > > > I prefer option 1 myself because it would be more performant than option > 2. > > > > > > On Fri, Sep 13, 2013 at 7:31 AM, John > wrote: > > > > > I have created a HBase Table in the hbase shell and added some data. In > > > http://hbase.apache.org/book/dm.sort.html is written that the datasets > > are > > > first sorted by the rowkey and then the column. So I tried something in > > the > > > HBase Shell: http://pastebin.com/gLVAX0rJ > > > > > > Everything looks fine. I got the right order a -> c -> d like expected. > > > > > > Now I tried the same with Apache Pig in Java: > > http://pastebin.com/jdTpj4Fu > > > > > > I got this result: > > > > > > (key1,[c#val,d#val,a#val]) > > > > > > So, now the order is c -> d -> a. That seems a little odd to me, > > shouldn't > > > it be the same like in HBase? It's important for me to get the right > > order > > > because I transform the map afterwards into a bag and then join it with > > > other tables. If both inputs are sorted I could use a merge join > without > > > sorting these two datasets. So does anyone know how it is possible to > get > > > the sorted map (or bag) of the columns? > > > > > > > > > thanks > > > > > >
Re: Sort Order in HBase with Pig/Piglatin in Java
Hi, thanks for your quick answer! I figured it out by my self since the mailing server was down the last 2hours?! Btw. I did option 1. But I used a LinkedHashMap insead. Do you knows whats the better choice? TreeMap or LinkedHashMap? Anyway thanks :) 2013/9/13 Pradeep Gollakota > Thats a great observation John! The problem is that HBaseStorage maps > columns families into a HashMap, so the sort ordering is completely lost. > > You have two options: > > 1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) and > use the modified HBaseStorage. (or make it configurable) > 2. Since you convert the map to a bag, you can sort the bag in a nested > foreach statement. > > I prefer option 1 myself because it would be more performant than option 2. > > > On Fri, Sep 13, 2013 at 7:31 AM, John wrote: > > > I have created a HBase Table in the hbase shell and added some data. In > > http://hbase.apache.org/book/dm.sort.html is written that the datasets > are > > first sorted by the rowkey and then the column. So I tried something in > the > > HBase Shell: http://pastebin.com/gLVAX0rJ > > > > Everything looks fine. I got the right order a -> c -> d like expected. > > > > Now I tried the same with Apache Pig in Java: > http://pastebin.com/jdTpj4Fu > > > > I got this result: > > > > (key1,[c#val,d#val,a#val]) > > > > So, now the order is c -> d -> a. That seems a little odd to me, > shouldn't > > it be the same like in HBase? It's important for me to get the right > order > > because I transform the map afterwards into a bag and then join it with > > other tables. If both inputs are sorted I could use a merge join without > > sorting these two datasets. So does anyone know how it is possible to get > > the sorted map (or bag) of the columns? > > > > > > thanks > > >
Re: Sort Order in HBase with Pig/Piglatin in Java
Thats a great observation John! The problem is that HBaseStorage maps columns families into a HashMap, so the sort ordering is completely lost. You have two options: 1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) and use the modified HBaseStorage. (or make it configurable) 2. Since you convert the map to a bag, you can sort the bag in a nested foreach statement. I prefer option 1 myself because it would be more performant than option 2. On Fri, Sep 13, 2013 at 7:31 AM, John wrote: > I have created a HBase Table in the hbase shell and added some data. In > http://hbase.apache.org/book/dm.sort.html is written that the datasets are > first sorted by the rowkey and then the column. So I tried something in the > HBase Shell: http://pastebin.com/gLVAX0rJ > > Everything looks fine. I got the right order a -> c -> d like expected. > > Now I tried the same with Apache Pig in Java: http://pastebin.com/jdTpj4Fu > > I got this result: > > (key1,[c#val,d#val,a#val]) > > So, now the order is c -> d -> a. That seems a little odd to me, shouldn't > it be the same like in HBase? It's important for me to get the right order > because I transform the map afterwards into a bag and then join it with > other tables. If both inputs are sorted I could use a merge join without > sorting these two datasets. So does anyone know how it is possible to get > the sorted map (or bag) of the columns? > > > thanks >