accesses versus sequential accesses, a (very crude) estimate of the
effects of caching on random page accesses, and cost to evaluate WHERE-
clause expressions. Export critical parameters for this model as SET
variables. Also, create SET variables for the planner's enable flags
(enable_seqscan, enable_indexscan, etc) so that these can be controlled
more conveniently than via PGOPTIONS.
Planner now estimates both startup cost (cost before retrieving
first tuple) and total cost of each path, so it can optimize queries
with LIMIT on a reasonable basis by interpolating between these costs.
Same facility is a win for EXISTS(...) subqueries and some other cases.
Redesign pathkey representation to achieve a major speedup in planning
(I saw as much as 5X on a 10-way join); also minor changes in planner
to reduce memory consumption by recycling discarded Path nodes and
not constructing unnecessary lists.
Minor cleanups to display more-plausible costs in some cases in
EXPLAIN output.
Initdb forced by change in interface to index cost estimation
functions.
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
^^^^ required
Also note that SET TRANSACTION ISOLATION LEVEL change
isolevel for _current_ transaction, in accordance with
standard, not for session (ALTER SESSION is used in Oracle,
but it's not implemented currently).
And I would don't mention SET XACTISOLEVEL TO ...
form at all.
Please update set.sgml - I failed to understand all these
SET TIME ZONE { '<REPLACEABLE CLASS="PARAMETER">
now.
for Vadim
