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HTAP - hybrid transactional/analytical processing

SG - serializability graph

Design Goals

To define key points of the protocol design, let's take a look at some features, which can be provided by the product, and value them from 1 to 3, where 3 means maximum importance for product success.

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Two actions on the same data object, modified by different transactions, conflict, if at least one of them is a write. The three anomalous situations can be described in terms of when the actions of two transactions T1 and T2 conflict with each other: in a write-read (WR) conflict T2 reads a data object previously written by T1; we define read-write (RW) and write-write (WW) conflicts similarly. These conflicts can cause anomalies like dirty reads, unrepeatable reads, lost updates, and others.

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It is useful to capture all potential conflicts between the transactions in a schedule in a precedence graph, also called a serializability graph (SG).

The precedence graph for a schedule S contains:

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TBD example of view serializable schedule but non CSR

Until now we have talked about schedules having only committed transactions. We must also take into consideration schedules containing aborted transactions (this can happen also due to internal error or a crash), which brings the recoverability notion for a schedule. 

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