Thread: Question about isolation level documentation
Is there a discussion somewhere regarding this line from the docs on transaction isolation: "When you select the level Read Uncommitted you really get Read Committed, and phantom reads are not possible in the PostgreSQL implementation of Repeatable Read"? I get that RU is the same as RC and why that is so, but why is RR mentioned in this sentence and more importantly why does it claim phantom reads aren't possible in RR despite the table above this paragraph clearly stating they are? It looks like a documentation issue associated with the true serialization mode introduced in 9.1.
Elliot S wrote: > Is there a discussion somewhere regarding this line from the docs on > transaction isolation: "When you select the level Read Uncommitted > you really get Read Committed, and phantom reads are not possible in > the PostgreSQL implementation of Repeatable Read"? I get that RU is > the same as RC and why that is so, but why is RR mentioned in this > sentence and more importantly why does it claim phantom reads aren't > possible in RR despite the table above this paragraph clearly > stating they are? It looks like a documentation issue associated > with the true serialization mode introduced in 9.1. I read that as saying that even though the standard defines repeatable read as possibly having phantom reads, they don't occur in Postgres. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
On 04/08/2014 04:09 PM, Alvaro Herrera wrote: > Elliot S wrote: >> Is there a discussion somewhere regarding this line from the docs on >> transaction isolation: "When you select the level Read Uncommitted >> you really get Read Committed, and phantom reads are not possible in >> the PostgreSQL implementation of Repeatable Read"? I get that RU is >> the same as RC and why that is so, but why is RR mentioned in this >> sentence and more importantly why does it claim phantom reads aren't >> possible in RR despite the table above this paragraph clearly >> stating they are? It looks like a documentation issue associated >> with the true serialization mode introduced in 9.1. > I read that as saying that even though the standard defines repeatable > read as possibly having phantom reads, they don't occur in Postgres. > Oh - duh - that makes sense. Thanks. For some reason I couldn't make the connection between the two clauses.