In the original implementation, a range-contained-by search had to scan
the entire index because an empty range could be lurking anywhere.
Improve that by adding a flag to upper GiST entries that says whether the
represented subtree contains any empty ranges.
Also, make a simple mod to the penalty function to discourage empty ranges
from getting pushed into subtrees without any. This needs more work, and
the picksplit function should be taught about it too, but that code can be
improved without causing an on-disk compatibility break; so we'll leave it
for another day.
Since we're breaking on-disk compatibility of range values anyway, I took
the opportunity to reorganize the range flags bits; the unused
RANGE_xB_NULL bits are now adjacent, which might open the door for using
them in some other way later.
In passing, remove the GiST range opclass entry for <>, which doesn't seem
like it can really be indexed usefully.
Alexander Korotkov, with some editorializing by Tom
The original coding would not work for discrete ranges in which the
canonicalization rule is to produce symmetric boundaries (either [] or ()
style), as noted by Jeff Davis. Florian Pflug pointed out that we could
fix that by invoking the canonicalization function to see if the range
"between" the two given ranges normalizes to empty. This implementation
of Florian's idea is a tad slower than the original code, but only in the
case where there actually is a canonicalization function --- if not, it's
essentially the same logic as before.
It's not clear that a per-datatype typanalyze function would be any more
useful than a generic typanalyze for ranges. What *is* clear is that
letting unprivileged users select typanalyze functions is a crash risk or
worse. So remove the option from CREATE TYPE AS RANGE, and instead put in
a generic typanalyze function for ranges. The generic function does
nothing as yet, but hopefully we'll improve that before 9.2 release.
Per discussion, the zero-argument forms aren't really worth the catalog
space (just write 'empty' instead). The one-argument forms have some use,
but they also have a serious problem with looking too much like functional
cast notation; to the point where in many real use-cases, the parser would
misinterpret what was wanted.
Committing this as a separate patch, with the thought that we might want
to revert part or all of it if we can think of some way around the cast
ambiguity.
Implement these tests directly instead of constructing a singleton range
and then applying range-contains. This saves a range serialize/deserialize
cycle as well as a couple of redundant bound-comparison steps, and adds
very little code on net.
Remove elem_contained_by_range from the GiST opclass: it doesn't belong
there because there is no way to use it in an index clause (where the
indexed column would have to be on the left). Its commutator is in the
opclass, and that's what counts.
Per discussion, relax the range input/construction rules so that the
only hard error is lower bound > upper bound. Cases where the lower
bound is <= upper bound, but the range nonetheless normalizes to empty,
are now permitted.
Fix core dump in range_adjacent when bounds are infinite. Marginal
cleanup of regression test cases, some more code commenting.
Move the responsibility for caching specialized information about range
types into the type cache, so that the catalog lookups only have to occur
once per session. Rearrange APIs a bit so that fn_extra caching is
actually effective in the GiST support code. (Use of OidFunctionCallN is
bad enough for performance in itself, but it also prevents the function
from exploiting fn_extra caching.)
The range I/O functions are still not very bright about caching repeated
lookups, but that seems like material for a separate patch.
Also, avoid unnecessary use of memcpy to fetch/store the range type OID and
flags, and don't use the full range_deserialize machinery when all we need
to see is the flags value.
Also fix API error in range_gist_penalty --- it was failing to set *penalty
for any case involving an empty range.
A range type whose element type has 'd' alignment must have 'd' alignment
itself, else there is no guarantee that the element value can be used
in-place. (Because range_deserialize uses att_align_pointer which forcibly
aligns the given pointer, violations of this rule did not lead to SIGBUS
but rather to garbage data being extracted, as in one of the added
regression test cases.)
Also, you can't put a toast pointer inside a range datum, since the
referenced value could disappear with the range datum still present.
For consistency with the handling of arrays and records, I also forced
decompression of in-line-compressed bound values. It would work to store
them as-is, but our policy is to avoid situations that might result in
double compression.
Add assorted regression tests for this, and bump catversion because of
fixes to built-in pg_type entries.
Also some marginal cleanup of inconsistent/unnecessary error checks.
Change range_lower and range_upper to return NULL rather than throwing an
error when the input range is empty or the relevant bound is infinite. Per
discussion, throwing an error seems likely to be unduly hard to work with.
Also, this is more consistent with the behavior of the constructors, which
treat NULL as meaning an infinite bound.
Change range_before, range_after, range_adjacent to return false rather
than throwing an error when one or both input ranges are empty.
The original definition is unnecessarily difficult to use, and also can
result in undesirable planner failures since the planner could try to
compare an empty range to something else while deriving statistical
estimates. (This was, in fact, the cause of repeatable regression test
failures on buildfarm member jaguar, as well as intermittent failures
elsewhere.)
Also tweak rangetypes regression test to not drop all the objects it
creates, so that the final state of the regression database contains
some rangetype objects for pg_dump testing.
No functional changes in this commit (except I could not resist the
temptation to re-word a couple of error messages). This is just manual
cleanup after pgindent to make the code look reasonably like other PG
code, in preparation for more detailed code review to come.
