Cloudera HBase Certification Questions and Answers (Dumps and Practice Questions)

Question :

Your client application calls the following method for all puts to the single table notifications:
'put.setWriteToWAL, (false);
One region, region1, for the notifications table is assigned to RegionServer rs1. Which of the following
statements describes the result of RegionServer rs1 crashing?


1. All data in the notifications table is lost
2. No data is lost
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4. Data for your client application in the MemStores for region1 is lost



Correct Answer : Get Lastest Questions and Answer :


Explanation: What role does 'setWriteToWAL(false)' play?
HBase uses a write ahead log, if you don't write to it you will lose all the data that's only in the memstores
when a region server fails.
This setting is useful for importing a lot of data.





Question :

You have a key-value pair size of l00 bytes. You increase your HFile block size from its default 64k. What
results from this change?


1. scan throughput increases and random-access latency decreases
2. scan throughput decreases and random-access latency increases
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4. scan throughput increases and random-access latency increases




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Explanation: Larger block size is preferred if files are primarily for sequential access. Smaller blocks are good for random
access, but require more memory to hold the block index, and may be slower to create





Question :

You have tin linage table live in production. The table users (timestamp) as the rowkey. You want to change
the existing rowkeys to (userid)(timestamp). Which of the following should you do?


1. Modify the client application to write to both the old table and a new table while migrating the old data separately
2. Use the ALTER table command to modify the rowkeys
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4. Add a new column to store the userid



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Explanation: Rowkeys cannot be changed. The only way they can be "changed" in a table is if the row is deleted and then
re-inserted. This is a fairly common question on the HBase dist-list so it pays to get the rowkeys right the first
time (and/or before you've inserted a lot of data).

Related Questions

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Question : There are two option as below to create HTable

1.
HBaseConfiguration conf = HBaseConfiguration.create();
HTable table1 = new HTable(conf, "myTable");
HTable table2 = new HTable(conf, "myTable");

2.
HBaseConfiguration conf1 = HBaseConfiguration.create();
HTable table1 = new HTable(conf1, "myTable");
HBaseConfiguration conf2 = HBaseConfiguration.create();
HTable table2 = new HTable(conf2, "myTable");

Which of the approach is recommended


1. Both 1 and 2 are equal
2. 1 is recommnded
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Question : HTable is a thread-safe and should not create a unique instance in each thread or and using HTablePool is not a good idea

1. True
2. false




Question : HBase uses byte arrays for ..


1. Row keys
2. column names
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4. All of the above





Question :

Which of the following operation is used to find single rowkey



1. Get
2. Find
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4. IsAvailable




Question :

HTables get method retrieves a Result object as below

Get g = new Get(Bytes.toBytes("rowkey"));
Result row = table.get(g);

Does this Result object holds all information about a row key ?


1. True
2. False




Question :

HTables get method retrieves a Result object as below

Get g = new Get(Bytes.toBytes("rowkey"));
Result row = table.get(g);

Select the correct statement from below


1. Column names known than use getValue or getFamilyMap to retrieve values
2. if not known use list or raw to iterate over the columns
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4. 1 and 3 are correct
5. 1 and 2 are correct