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Mapr (HP) HBase Developer Certification Questions and Answers (Dumps and Practice Questions)



Question :

Yon are storing page view data for a large number of Web sites, each of which has many subdomains (www.
example.com, archive.example.com, beta.example.com, etc.) Your reporting tool needs to retrieve the total
number of page views for a given subdomain of a Web site. Which of the following rowkeys should you use?
:
1. The reverse domain name (e.g., com.example.beta)
2. The domain name followed by the URL
 3. Access Mostly Uused Products by 50000+ Subscribers
4. The URL followed by the reverse domain name

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Consider a table whose keys are domain names. It makes the most sense to list them in reverse notation (so
"com.jimbojw.www" rather than "www.jimbojw.com") so that rows about a subdomain will be near the parent
domain row. Continuing the domain example, the row for the domain "mail.jimbojw.com" would be right next to
the row for "www.jimbojw.com" rather than say "mail.xyz.com" which would happen if the keys were regular
domain notation.





Question :

Your client is writing to a region when the RegionServer crashes. At what point in the write is your data
secure?

:
1. From the moment the RegionServer wrote to the WAL (write-ahead log)
2. From the moment the RegionServer returned the call
 3. Access Mostly Uused Products by 50000+ Subscribers
4. From the moment the RegionServer wrote to the MemStore



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Each RegionServer adds updates (Puts, Deletes) to its write-ahead log (WAL) first, and then to the Section
9.7.5.1, "MemStore" for the affected Section 9.7.5, "Store". This ensures that HBasehas durable writes.
Without WAL, there is the possibility of data loss in the case of a RegionServer failure before each MemStore
is flushed and new StoreFiles are written. HLog is the HBase WAL implementation, and there is one HLog
instance per RegionServer.

Note:
In computer science, write-ahead logging (WAL) is a family of techniques for providing atomicity and durability
(two of the ACID properties) in database systems. In a system using WAL, all modifications are written to a log
before they are applied. Usually both redo and undo information is stored in the log.
The purpose of this can be illustrated by an example. Imagine a program that is in the middle of performing
some operation when the machine it is running on loses power. Upon restart, that program might well need to
know whether the operation it was performing succeeded, half- succeeded, or failed. If a write-ahead log were
used, the program could check this log and compare what it was supposed to be doing when it unexpectedly
lost power to what was actually done. On the basis of this comparison, the program could decide to undo what
it had started, complete what it had started, or keep things as they are. WAL allows updates of a database to
be done in-place. Another way to implement atomic updates is with shadow paging, which is not in-place. The
main advantage of doing updates in-place is that it reduces the need to modify indexes and block lists.





Question :

Given the following HBase dataset, which is labeled with row numbers. . .

1 BB002 Column=Comments:C_Author,timestamp=001,value=Diana Mears
2 BB002 Column=Comments:C_Title,timestamp=001,value=Thanks
3 BB001 Column=INFO:Title,timestamp=005,value=HBase+Hadoop
4 BB001 Column=INFO:Author,timestamp=005,value=Larse George
5 BB002 Column=Comments:C_Text,timestamp=001,value=Any tips on...
3 BB001 Column=INFO:Text,timestamp=005,value=Some of the...

Which of the following lists of row numbers is the correct order that HBase would store this data?

:
1. 1, 5, 2, 4, 3, 6
2. 4, 1, 2, 6, 3, 5
 3. Access Mostly Uused Products by 50000+ Subscribers
4. 3, 4, 6, 1, 2, 5



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Related Questions

Question : Given the following HBase code:

HTable customers = new HTable(hconf, "customers");
byte [] rowKey = Bytes.toBytes(65);
Put put = new Put(rowKey);
put.add("info".getBytes(), "FirstName".getBytes(), "Kimberly".getBytes());
put.add("info".getBytes(), "LastName".getBytes(), "Grant".getBytes());

What line of code adds this data to the table named "customers"?


 : Given the following HBase code:
1. put.insertRow(customers);
2. put.add(customers);
3. Access Mostly Uused Products by 50000+ Subscribers
4. customers.add(put);



Question : Given the following HBase code:
byte [] rowKey = Bytes.toBytes(65);
Get get = new Get(rowKey);
Result result = customers.get(get);

Which one of the following statements is true?


 : Given the following HBase code:
1. The result variable will contain all values from all column families for the row whose key is 65
2. The result variable in this example will always be null
 3. Access Mostly Uused Products by 50000+ Subscribers
4. The result variable will not contain any values and can be used for retrieving the column values



Question : Given the following HBase code:

byte [] rowKey = Bytes.toBytes(65);
Get get = new Get(rowKey);
get.addFamily("info".getBytes());
Result result = customers.get(get);

Which one of the following statements is true?



: Given the following HBase code:
1. The method call to addFamily does not compile
2. The result will contain all values from all column families for the row whose key is 65
 3. Access Mostly Uused Products by 50000+ Subscribers
4. The result will contain all values from the "info" column qualifier for the row whose key is 65



Question :

Yon are storing page view data for a large number of Web sites, each of which has many subdomains (www.
example.com, archive.example.com, beta.example.com, etc.) Your reporting tool needs to retrieve the total
number of page views for a given subdomain of a Web site. Which of the following rowkeys should you use?
 :
1. The reverse domain name (e.g., com.example.beta)
2. The domain name followed by the URL
 3. Access Mostly Uused Products by 50000+ Subscribers
4. The URL followed by the reverse domain name


Question :

Your client is writing to a region when the RegionServer crashes. At what point in the write is your data
secure?

 :
1. From the moment the RegionServer wrote to the WAL (write-ahead log)
2. From the moment the RegionServer returned the call
 3. Access Mostly Uused Products by 50000+ Subscribers
4. From the moment the RegionServer wrote to the MemStore




Question :

Given the following HBase dataset, which is labeled with row numbers. . .

1 BB002 Column=Comments:C_Author,timestamp=001,value=Diana Mears
2 BB002 Column=Comments:C_Title,timestamp=001,value=Thanks
3 BB001 Column=INFO:Title,timestamp=005,value=HBase+Hadoop
4 BB001 Column=INFO:Author,timestamp=005,value=Larse George
5 BB002 Column=Comments:C_Text,timestamp=001,value=Any tips on...
3 BB001 Column=INFO:Text,timestamp=005,value=Some of the...

Which of the following lists of row numbers is the correct order that HBase would store this data?

 :
1. 1, 5, 2, 4, 3, 6
2. 4, 1, 2, 6, 3, 5
 3. Access Mostly Uused Products by 50000+ Subscribers
4. 3, 4, 6, 1, 2, 5