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Redesign query-snapshot timing so that volatile functions in READ COMMITTED

mode see a fresh snapshot for each command in the function, rather than
using the latest interactive command's snapshot.  Also, suppress fresh
snapshots as well as CommandCounterIncrement inside STABLE and IMMUTABLE
functions, instead using the snapshot taken for the most closely nested
regular query.  (This behavior is only sane for read-only functions, so
the patch also enforces that such functions contain only SELECT commands.)
As per my proposal of 6-Sep-2004; I note that I floated essentially the
same proposal on 19-Jun-2002, but that discussion tailed off without any
action.  Since 8.0 seems like the right place to be taking possibly
nontrivial backwards compatibility hits, let's get it done now.
This commit is contained in:
Tom Lane
2004-09-13 20:10:13 +00:00
parent d69528881a
commit b2c4071299
41 changed files with 1764 additions and 834 deletions

View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.23 2004/05/16 23:22:07 neilc Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.24 2004/09/13 20:05:18 tgl Exp $ -->
<chapter id="plpython">
<title>PL/Python - Python Procedural Language</title>
@ -175,7 +175,7 @@ def __plpython_procedure_myfunc_23456():
row number and column name. It has these additional methods:
<function>nrows</function> which returns the number of rows
returned by the query, and <function>status</function> which is the
<function>SPI_exec()</function> return value. The result object
<function>SPI_execute()</function> return value. The result object
can be modified.
</para>