Transakce ...tam a zase zpátky

Ondřej Chaloupka

jOpenSpace 2019

Jsou transakce zlo?

Databáze

https://www.root.cz/clanky/historie-relacnich-databazi

1983
ACID

Principles of Transaction-Oriented Database Recovery, Andreas Reuter and Theo Härde, 1983

1980*
relační databáze

Transakce jsou...

abstrakce pro jednoduchou práci s daty

ACID

Atomicity

Consistency

Isolation

Durability

Transactions: myths, surprises and opportunities" by Martin Kleppmann

Atomicity == vrácení dat do původního stavu

ACID

ACID

Consistency == data jsou konzistentní

Durability == data jsou bezpečně uloženy

ACID

Isolation == data je možné zpracovávat paralelně

Serializability !

Lock-based

ID	Jméno	Příjmení
1	Zdeněk	Henek
2	Jan	Novotný

Lock-based for serializability

ID	Jméno	Příjmení
1	Zdeněk	Henek
2	Jan	Novotný

Lock-based isolation levels

Isolation level	Dirty reads	Lost updates	Non-repeatable reads	Phantoms
Read Uncommitted	may occur	may occur	may occur	may occur
Read Committed	don't occur	may occur	may occur	may occur
Repeatable Read	don't occur	don't occur	don't occur	may occur
Serializable	don't occur	don't occur	don't occur	don't occur

https://en.wikipedia.org/wiki/Isolation_(database_systems)

Databáze a transakce

1983
ACID

First version of ANSI SQL was in 1987
A Critique of ANSI SQL Isolation Levels, Hal Berenson, Phil Bernstein 1995

1980*
relační databáze

1992
ANSI SQL

1995
Critique on ACID

Lock-based vs. MVCC

https://medium.com/@FranckPachot/mvcc-in-oracle-vs-postgres-and-a-little-no-bloat-beauty-e3a04d6a8bd2

CAP a distribuované databáze

1983
ACID

1980*
relační databáze

1992
ANSI SQL

1995
Critique on ACID

2000
CAP

Brewer’s CAP Theorem, 2000
The Part-Time Parliament, Leslie Lamport, 1998
Paxos Made Simple, Leslie Lamport, 2001

2001
Paxos simple

CAP theorem

https://towardsdatascience.com/cap-theorem-and-distributed-database-management-systems-5c2be977950e

CAP Consistency != ACID consistency

Availability over Consistency

1983
ACID

Amazon's dynamo paper, Amazon, 2007

1980*
relační databáze

1992
ANSI SQL

1995
Critique on ACID

2000
CAP

2001
Paxos simple

2007
Dynamo paper

NoSQL era

Consistency strikes back

CRDT: Conflict-free replicated data types, Shapiro, 2011
Spanner, Google, 2012
Calvin, A. Thomson, D. Abadi 2012
Jepsen.io analyses, Kyle Kingsbury

2012
Spanner

NewSQL era

2011
CRDT

1983
ACID

1980*
relační databáze

1992
ANSI SQL

1995
Critique on ACID

2000
CAP

2001
Paxos simple

2007
Dynamo paper

NoSQL to NewSQL

https://medium.com/rabiprasadpadhy/google-spanner-a-newsql-journey-or-beginning-of-the-end-of-the-nosql-era-3785be8e5c38

A co aplikace?

2011
Microservices

1991
XA spec

2008
BASE

"Dva největší problémy při programování jsou invalidace cache, pojmenování věcí a chyby o jedničku."

Martin Kleppmann: Transactions: myths, surprises and opportunities

?

2011
Microservices

1991
XA spec

Saga pattern/comensation transactions
Protocols for "client-side" distributed transactions
Event-sourcing message based approach (Kafka and friends)

2008
BASE

2019
?

DÍKY ZA POZORNOST