Why use a READ UNCOMMITTED isolation level?

A transaction ID (txid) is not authoritative. Absence of a txid in the blockchain does not mean the transaction was not processed. This is known as “transaction malleability,” because transactions can be modified prior to confirmation in a block, changing their txids. After a transaction is included in a block, its txid cannot change unless there i

That brings us to this rule: Have only one copy of any given piece of data. Instead of copying data into two places on the system, instead link data from one part of the information system to the other.

MapReduce is not a database, so it has no built-in security, no indexing, no query or process optimizer, no historical perspective in terms of other jobs that have been run, and no knowledge of other data that exists.

There are a few downsides to a table-based EADS. First is that the enterprise analytic data set tables will not be fully up-to-date with the latest data. Second is that they will use disk space on the system, potentially a whole lot of it.