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.
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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.
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�lvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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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.
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