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SQL v/s NoSQL: Amazon v/s eBay and the false premise of NoSQL


Here is the poll data from the Confio-sponsored webinar “NoSQL and Big Data for the Oracle DBA” and my answers to the questions asked in the chat. The recording of the webinar is now available at http://www.confio.com/webinars/nosql-big-data/. The slide deck is at http://iggyfernandez.files.wordpress.com/2013/10/nosql-and-big-data-for-oracle-dbas-oct-2013.pdf.

Are NoSQL products and technologies being deployed at your organization?
Total Responses: 145 of 303 (48%)
Answer Total Number Total %
Yes 39 27%
No 106 73%
Are Big Data products and technologies being deployed at your organization?
Total Responses: 138 of 303 (46%)
Answer Total Number Total %
Yes 52 38%
No 86 62%
Is there any merit to the claim that NoSQL technology beats relational technology in performance, scalability, and availability?
Total Responses: 143 of 303 (47%)
Answer Total Number Total %
No merit whatsoever 5 3%
Some merit 38 27%
A lot of merit 6 4%
Don’t have enough information to judge 94 66%

SQL v/s NoSQL

Q. Where would I use a NoSQL database v/s Cloudera Hadoop? (G. B.)

A. You would use a NoSQL database where you are dealing with simple schemas such as in the Amazon examples. You would use Cloudera Hadoop when you want to process large amounts of filesystem data using the parallel capabilities of the Map/Reduce algorithm.

Q. I’m a little confused on the objective of the webinar. Is it to indicate that a NoSQL solution is always unnecessary and one can use Oracle? Or that there are situations where a NoSQL data store is relevant and one can still use Oracle? Or something else? (R. B.)

A. There are certainly situations where NoSQL technologies excel, specifically situations that benefit from sharding and replication. However, the eBay example proves that it is also possible to design a modern e-commerce platform without completely abandoning relational technology. The unstated objective of the presentation was to prove that Amazon missed the opportunity to take relational technology to the next level. Amazon believed that relational technology requires a join penalty but it was wrong. See my post http://iggyfernandez.wordpress.com/2013/07/28/no-to-sql-and-no-to-nosql/.

Q. Are you implying that NoSQL is a solution for everything relational or that it has areas where it excels?  What are those areas for NoSQL vs. Relational? (C. R.)

A. Answered above.

Q. Are you also going to discuss the cost of Oracle v/s NoSQL? (D. T.)

A. Many NoSQL technologies are open-source. However, there is an argument to be made that you get what you pay for. Oracle Database is a feature-rich and mature product.

Q. If I understood your explanations, you mean that Oracle, through the 12c version, is now able to create data or reorganize any existing ones the NoSQL way and then can still use the powerful SQL language which does not require high technical skills? (J. M. A.)

Clusters have been available in Oracle Database for an extremely long time. For example, refer to the Oracle7 Server Concepts Manual at http://docs.oracle.com/cd/A57673_01/DOC/server/doc/SCN73/ch5.htm#toc052. Object-relational capabilities were introduced in Oracle Database 8.0.

Q. Is there a benefit for eBay to transfer its data into NoSQL clusters given it is already using Oracle the SQL way? (J. M. A.)

The eBay example proves that it is also possible to design a modern e-commerce platform without completely abandoning relational technology.

Clusters

Q. Why do you think people are not using clustered tables? Are there any downsides with it? (A. K. E.)

A. They are not used because most application developers and database administrators haven’t heard of them even though Oracle uses them for data dictionary tables such as TAB$ and COL$ and even though Oracle uses single-table hash clusters in TPC-C benchmarks.

Clusters cannot be partitioned but you could use partition views to emulate partitioning as in the example at http://iggyfernandez.wordpress.com/2013/01/22/we-dont-use-databases-we-dont-use-indexes/. Note that Oracle used an undocumented patch to partition hash clusters in a recent TPC-C benchmark. See http://iggyfernandez.wordpress.com/2011/05/10/major-new-undocumented-partitioning-feature-in-oracle-database-11g-release-2/.

One issue with hash clusters is the potential for hash collisions and block chains. In the TPC-C benchmarks, Oracle pre-allocates space for all the expected rows and uses the “HASH IS” clause to prevent hash collisions. An alternative is to use indexed clusters.

Q. What if you have large tables in terms of rows. How will table clusters perform? (T. D.)

A. Clusters cannot be partitioned but you could use partition views to emulate partitioning as in the example at http://iggyfernandez.wordpress.com/2013/01/22/we-dont-use-databases-we-dont-use-indexes/. Note that parallel UNION ALL is only available in Oracle Database 12c. Note that Oracle used an undocumented patch to partition hash clusters in a recent TPC-C benchmark. See http://iggyfernandez.wordpress.com/2011/05/10/major-new-undocumented-partitioning-feature-in-oracle-database-11g-release-2/ so it is not unreasonable to hope that the feature will be implemented someday.

Q. How will table clusters perform for large amounts of data? (M. R.)

A. Answered above.

Q. Is there a multi-block read penalty for blocks that are read from the clustered tables in your example when you want to report across all employees? (K. H.)

A. Yes, there is a penalty. But NoSQL optimizes for a specific use case and we did the same. It is good practice to optimize for the most important use case. In the example, we optimized for the use case of retrieving all data for a single employee.

Q. How about the employee object-relational view. Doesn’t it use join operations in the background at the time of select? (K. N.)

A. Yes, it does. But the query execution plan shows that there is no join penalty. When retrieving one row from the view, the estimated cost is 1 and the actual number of blocks touched is also 1.

Big Data

Q. You mentioned writing Java code [for Hadoop]. How about using C++, Python, etc.? (K. Z.)

A. See http://www.michael-noll.com/tutorials/writing-an-hadoop-mapreduce-program-in-python/.

Q. How does what you present compare to Aster SQL/MapReduce? (L. L.)

A. The detailed explanation is in Aster Data’s paper “SQL/MapReduce: A practical approach to self-describing, polymorphic, and parallelizable user-defined functions” available at http://pdf.aminer.org/000/225/039/a_practical_approach_to_static_node_positioning.pdf. You might also want to read Oracle’s paper “In-Database Map-Reduce” available at http://www.oracle.com/technetwork/database/bi-datawarehousing/twp-indatabase-mapreduce-128831.pdf.

Q. What is the best database to load Twitter and Facebook data and analyze? (G.B.)

A. Facebook cannot provide public access to user posts because of privacy restrictions but Twitter provides public access to its tweet stream. The choice of technology for analyzing the tweet stream depends on the kind of analysis. Last year, Twitter engineers made presentations on the Twitter architecture to students at the University of California at Berkeley. For their projects, the students analyzed the Twitter data using various technologies. The architecture presentations by the Twitter engineers and the project presentations by the students are available at http://blogs.ischool.berkeley.edu/i290-abdt-s12/. The “map of a tweet” is at http://www.scribd.com/doc/30146338/map-of-a-tweet.

Predictions

Q. What skills can an Oracle DBA take to use in Big Data world? (G. B.)

A. In the Big Data world, you’re probably going to need Linux, SQL, and programming skills. You can leverage your previous experience as an administrator or an application developer.

Q. Assuming NoSQL takes over, what do you think will be the roles of Database Administrators? (K. I.)

A. I don’t foresee NoSQL taking over. But I see innovation continuing in the relational and non-relational spaces. I see relational and non-relational systems co-existing. I see some companies winning and some companies losing. I see both the relational and non-relational camps adopting each other’s best ideas. However, the tasks will remain the same; that is, installing, configuring, upgrading, monitoring, tuning, programming, etc.

Q. With Big Data and the Cloud coming into the picture, will roles like Oracle DBA and SQL Server DBA be replaced by Big Data DBA and Cloud DBA roles? (V. V.)

A. They won’t be replaced because Oracle Database and SQL Server are not going away.

Q. If NoSQL people are reinventing SQL in one way or another, then what is the future of SQL? (J. G.)

A. Relational algebra is the right tool for a lot of tasks, so the future of SQL is assured.

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