that it's good to join where there are join clauses rather than where there
are not. Also enable it to generate bushy plans at need, so that it doesn't
fail in the presence of multiple IN clauses containing sub-joins. These
changes appear to improve the behavior enough that we can substantially reduce
the default pool size and generations count, thereby decreasing the runtime,
and yet get as good or better plans as we were getting in 7.4. Consequently,
adjust the default GEQO parameters. I also modified the way geqo_effort is
used so that it affects both population size and number of generations;
it's now useful as a single control to adjust the GEQO runtime-vs-plan-quality
tradeoff. Bump geqo_threshold to 12, since even with these changes GEQO
seems to be slower than the regular planner at 11 relations.
default value for geqo_effort is supposed to be 40, not 1. The actual
'genetic' component of the GEQO algorithm has been practically disabled
since 7.1 because of this mistake. Improve documentation while at it.
sequence every time it's called is bogus --- it interferes with user
control over the seed, and actually decreases randomness overall
(because a seed based on time(NULL) is pretty predictable). If you really
want a reproducible result from geqo, do 'set seed = 0' before planning
a query.
allocation in best_inner_indexscan(). While at it, simplify GEQO's
interface to the main planner --- make_join_rel() offers exactly the
API it really wants, whereas calling make_rels_by_clause_joins() and
make_rels_by_clauseless_joins() required jumping through hoops.
Rewrite gimme_tree for clarity (sometimes iteration is much better than
recursion), and approximately halve GEQO's runtime by recognizing that
tours of the forms (a,b,c,d,...) and (b,a,c,d,...) are equivalent
because of symmetry in make_join_rel().
PX recombination operator, changes some elog() messages from LOG
to DEBUG1, puts some debugging functions inside the appropriate
#ifdef (not enabled by default), and makes a few other minor
cleanups.
BTW, the elog() change is motivated by at least one user who
has sent a concerned email to -general asking exactly what the
"ERX recombination operator" is, and what it is doing to their
DBMS.
Neil Conway
query representation. Note that GEQO_RELS setting is now interpreted
as the number of top-level items in the FROM list, not necessarily the
number of relations in the query. This seems appropriate since we are
only doing join-path searching over the top-level items.
for details). It doesn't really do that much yet, since there are no
short-term memory contexts in the executor, but the infrastructure is
in place and long-term contexts are handled reasonably. A few long-
standing bugs have been fixed, such as 'VACUUM; anything' in a single
query string crashing. Also, out-of-memory is now considered a
recoverable ERROR, not FATAL.
Eliminate a large amount of crufty, now-dead code in and around
memory management.
Fix problem with holding off SIGTRAP, SIGSEGV, etc in postmaster and
backend startup.
That means you can now set your options in either or all of $PGDATA/configuration,
some postmaster option (--enable-fsync=off), or set a SET command. The list of
options is in backend/utils/misc/guc.c, documentation will be written post haste.
pg_options is gone, so is that pq_geqo config file. Also removed were backend -K,
-Q, and -T options (no longer applicable, although -d0 does the same as -Q).
Added to configure an --enable-syslog option.
changed all callers from TPRINTF to elog(DEBUG)
