On 08/07/2012 09:45 PM, Kevin Grittner wrote:
I also think it's a problem that one can get through the entire
"Concurrency Control" chapter (mvcc.sgml) without a clue that
sequences aren't transactional. I think maybe a mention in the
Introduction section of that chapter with a <ref> would be
appropriate.
How about this? Is it accurate to suggest that sequences behave as if
they were always in "dirty read" isolation? Or would you instead say
that "changes made to a sequence are immediately visible to all other
transactions" ?
[PATCH] Make sure you can't read through mvcc.sgml without realising
that SEQUENCEs and SERIAL don't follow the rules.
---
doc/src/sgml/mvcc.sgml | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
new file mode 100644
index 8f88582..eed1f85
*** a/doc/src/sgml/mvcc.sgml
--- b/doc/src/sgml/mvcc.sgml
***************
*** 260,265 ****
--- 260,276 ----
command <xref linkend="sql-set-transaction">.
</para>
+ <important>
+ <para>
+ Some PostgreSQL data types and functions have special transactional
+ behaviour. Notably, SEQUENCEs
+ behave as if the isolation level is Dirty Read, irrespective
+ of the current isolation level, and are exempt from transaction
+ rollback. See <xref linkend="functions-sequence">.
+ SEQUENCEs are used by the SERIAL data types. See <xref
linkend="datatype-serial">.
+ </para>
+ </important>
+
<sect2 id="xact-read-committed">
<title>Read Committed Isolation Level</title>
--
1.7.11.2
--
Craig Ringer
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