If convert_to_scalar is passed a pair of datatypes it can't cope with,
its former behavior was just to elog(ERROR). While this is OK so far as
the core code is concerned, there's extension code that would like to use
scalarltsel/scalargtsel/etc as selectivity estimators for operators that
work on non-core datatypes, and this behavior is a show-stopper for that
use-case. If we simply allow convert_to_scalar to return FALSE instead of
outright failing, then the main logic of scalarltsel/scalargtsel will work
fine for any operator that behaves like a scalar inequality comparison.
The lack of conversion capability will mean that we can't estimate to
better than histogram-bin-width precision, since the code will effectively
assume that the comparison constant falls at the middle of its bin. But
that's still a lot better than nothing. (Someday we should provide a way
for extension code to supply a custom version of convert_to_scalar, but
today is not that day.)
While poking at this issue, we noted that the existing code for handling
type bytea in convert_to_scalar is several bricks shy of a load.
It assumes without checking that if the comparison value is type bytea,
the bounds values are too; in the worst case this could lead to a crash.
It also fails to detoast the input values, so that the comparison result is
complete garbage if any input is toasted out-of-line, compressed, or even
just short-header. I'm not sure how often such cases actually occur ---
the bounds values, at least, are probably safe since they are elements of
an array and hence can't be toasted. But that doesn't make this code OK.
Back-patch to all supported branches, partly because author requested that,
but mostly because of the bytea bugs. The change in API for the exposed
routine convert_network_to_scalar() is theoretically a back-patch hazard,
but it seems pretty unlikely that any third-party code is calling that
function directly.
Tomas Vondra, with some adjustments by me
Discussion: https://postgr.es/m/b68441b6-d18f-13ab-b43b-9a72188a4e02@2ndquadrant.com
This addresses only those cases that are easy to fix by adding or
moving a const qualifier or removing an unnecessary cast. There are
many more complicated cases remaining.
"consistent" functions, and remove pg_amop.opreqcheck, as per recent
discussion. The main immediate benefit of this is that we no longer need
8.3's ugly hack of requiring @@@ rather than @@ to test weight-using tsquery
searches on GIN indexes. In future it should be possible to optimize some
other queries better than is done now, by detecting at runtime whether the
index match is exact or not.
Tom Lane, after an idea of Heikki's, and with some help from Teodor.
* new split algorithm (as proposed in http://archives.postgresql.org/pgsql-hackers/2006-06/msg00254.php)
* possible call pickSplit() for second and below columns
* add spl_(l|r)datum_exists to GIST_SPLITVEC -
pickSplit should check its values to use already defined
spl_(l|r)datum for splitting. pickSplit should set
spl_(l|r)datum_exists to 'false' (if they was 'true') to
signal to caller about using spl_(l|r)datum.
* support for old pickSplit(): not very optimal
but correct split
* remove 'bytes' field from GISTENTRY: in any case size of
value is defined by it's type.
* split GIST_SPLITVEC to two structures: one for using in picksplit
and second - for internal use.
* some code refactoring
* support of subsplit to rtree opclasses
TODO: add support of subsplit to contrib modules
- Fix wrong index results on text, char, varchar for multibyte strings
- Fix some SIGFPE signals
- Add support for infinite timestamps
- Because of locale settings, btree_gist can not be a prefix index anymore (for text).
Each node holds now just the lower and upper boundary.
