MIN/MAX not be converted to use an index if the query WHERE clause contains
any volatile functions or subplans.
I had originally feared that the conversion might alter the behavior of such a
query with respect to a volatile function. Well, so it might, but only in the
sense that the function would get evaluated at a subset of the table rows
rather than all of them --- and we have never made any such guarantee anyway.
(For instance, we don't refuse to use an index for an ordinary non-aggregate
query when one of the non-indexable filter conditions contains a volatile
function.)
The prohibition against subplans was because of worry that that case wasn't
adequately tested, which it wasn't, but it turns out to be possible to make
8.1 fail anyway:
regression=# select o.ten, (select max(unique2) from tenk1 i where ten = o.ten
or ten = (select f1 from int4_tbl limit 1)) from tenk1 o;
ERROR: direct correlated subquery unsupported as initplan
This is due to bogus code in SS_make_initplan_from_plan (it's an initplan,
ergo it can't have any parParams). Having fixed that, we might as well allow
subplans as well as initplans.
qualification when the underlying operator is indexable and useOr is true.
That is, indexkey op ANY (ARRAY[...]) is effectively translated into an
OR combination of one indexscan for each array element. This only works
for bitmap index scans, of course, since regular indexscans no longer
support OR'ing of scans. There are still some loose ends to clean up
before changing 'x IN (list)' to translate as a ScalarArrayOpExpr;
for instance predtest.c ought to be taught about it. But this gets the
basic functionality in place.
comment line where output as too long, and update typedefs for /lib
directory. Also fix case where identifiers were used as variable names
in the backend, but as typedefs in ecpg (favor the backend for
indenting).
Backpatch to 8.1.X.
or OFFSET clauses by using estimate_expression_value(). The main advantage
of this is that if the expression is a Param and we have a value for the
Param, we'll use that value rather than defaulting. Also, fix some
thinkos in the logic for combining LIMIT/OFFSET with an externally
supplied tuple fraction (this covers cases like EXISTS(...LIMIT...)).
And make sure the results of all this are shown by EXPLAIN. Per a
gripe from Merlin Moncure.
planning logic for bitmap indexscans. Partial indexes create corner
cases in which a scan might be done with no explicit index qual conditions,
and the code wasn't handling those cases nicely. Also be a little
tenser about eliminating redundant clauses in the generated plan.
Per report from Dmitry Karasik.
a new PlannerInfo struct, which is passed around instead of the bare
Query in all the planning code. This commit is essentially just a
code-beautification exercise, but it does open the door to making
larger changes to the planner data structures without having to muck
with the widely-known Query struct.
but the code is basically working. Along the way, rewrite the entire
approach to processing OR index conditions, and make it work in join
cases for the first time ever. orindxpath.c is now basically obsolete,
but I left it in for the time being to allow easy comparison testing
against the old implementation.
be supported for all datatypes. Add CREATE AGGREGATE and pg_dump support
too. Add specialized min/max aggregates for bpchar, instead of depending
on text's min/max, because otherwise the possible use of bpchar indexes
cannot be recognized.
initdb forced because of catalog changes.
into indexscans on matching indexes. For the moment, it only handles
int4 and text datatypes; next step is to add a column to pg_aggregate
so that all MIN/MAX aggregates can be handled. Per my recent proposal.
