Presently, pg_popcount() processes data in 32-bit or 64-bit chunks
when possible. Newer hardware that supports AVX-512 instructions
can use 512-bit chunks, which provides a nice speedup, especially
for larger buffers. This commit introduces the infrastructure
required to detect compiler and CPU support for the required
AVX-512 intrinsic functions, and it adds a new pg_popcount()
implementation that uses these functions. If CPU support for this
optimized implementation is detected at runtime, a function pointer
is updated so that it is used by subsequent calls to pg_popcount().
Most of the existing in-tree calls to pg_popcount() should benefit
from these instructions, and calls with smaller buffers should at
least not regress compared to v16. The new infrastructure
introduced by this commit can also be used to optimize
visibilitymap_count(), but that is left for a follow-up commit.
Co-authored-by: Paul Amonson, Ants Aasma
Reviewed-by: Matthias van de Meent, Tom Lane, Noah Misch, Akash Shankaran, Alvaro Herrera, Andres Freund, David Rowley
Discussion: https://postgr.es/m/BL1PR11MB5304097DF7EA81D04C33F3D1DCA6A%40BL1PR11MB5304.namprd11.prod.outlook.com
For a long time, our outfuncs.c code has supposed that the string
contents of a BitString node could just be printed literally with
no concern for quoting/escaping. Now, that's okay if the string
literal contains only valid binary or hex digits ... but our lexer
doesn't check that, preferring to let bitin() be the sole authority
on what's valid. So we could have raw parse trees that contain
incorrect BitString literals, and that can result in failures when
WRITE_READ_PARSE_PLAN_TREES debugging is enabled.
Fix by using outToken() to print the string field, and debackslash()
to read it. This results in a change in the emitted representation
only in cases that would have failed before, and don't represent valid
SQL in the first place. Between that and the fact that we don't store
raw parse trees in the catalogs, I judge this safe to apply without a
catversion bump.
Per bug #18340 from Alexander Lakhin. Back-patch to v16; before that,
we lacked readfuncs support for BitString nodes, so that the problem
was only cosmetic.
Discussion: https://postgr.es/m/18340-4aa1ae6ed4121912@postgresql.org
pg_input_error_info() is now a SQL function able to return a row with
more than just the error message generated for incorrect data type
inputs when these are able to handle soft failures, returning more
contents of ErrorData, as of:
- The error message (same as before).
- The error detail, if set.
- The error hint, if set.
- SQL error code.
All the regression tests that relied on pg_input_error_message() are
updated to reflect the effects of the rename.
Per discussion with Tom Lane and Andrew Dunstan.
Author: Nathan Bossart
Discussion: https://postgr.es/m/139a68e1-bd1f-a9a7-b5fe-0be9845c6311@dunslane.net
This function for bit and bytea counts the set bits in the bit or byte
string. Internally, we use the existing popcount functionality.
For the name, after some discussion, we settled on bit_count, which
also exists with this meaning in MySQL, Java, and Python.
Author: David Fetter <david@fetter.org>
Discussion: https://www.postgresql.org/message-id/flat/20201230105535.GJ13234@fetter.org
If the substring start index and length overflow when added together,
substring() misbehaved, either throwing a bogus "negative substring
length" error on a case that should succeed, or failing to complain that
a negative length is negative (and instead returning the whole string,
in most cases). Unsurprisingly, the text, bytea, and bit variants of
the function all had this issue. Rearrange the logic to ensure that
negative lengths are always rejected, and add an overflow check to
handle the other case.
Also install similar guards into detoast_attr_slice() (nee
heap_tuple_untoast_attr_slice()), since it's far from clear that
no other code paths leading to that function could pass it values
that would overflow.
Patch by myself and Pavel Stehule, per bug #16804 from Rafi Shamim.
Back-patch to v11. While these bugs are old, the common/int.h
infrastructure for overflow-detecting arithmetic didn't exist before
commit 4d6ad3125, and it doesn't seem like these misbehaviors are bad
enough to justify developing a standalone fix for the older branches.
Discussion: https://postgr.es/m/16804-f4eeeb6c11ba71d4@postgresql.org
Commit 5ac0d9360 failed to entirely fix bitshiftright's habit of
leaving one-bits in the pad space that should be all zeroes,
because in a moment of sheer brain fade I'd concluded that only
the code path used for not-a-multiple-of-8 shift distances needed
to be fixed. Of course, a multiple-of-8 shift distance can also
cause the problem, so we need to forcibly zero the extra bits
in both cases.
Per bug #16037 from Alexander Lakhin. As before, back-patch to all
supported branches.
Discussion: https://postgr.es/m/16037-1d1ebca564db54f4@postgresql.org
If the bitstring length is not a multiple of 8, we'd shift the
rightmost bits into the pad space, which must be zeroes --- bit_cmp,
for one, depends on that. This'd lead to the result failing to
compare equal to what it should compare equal to, as reported in
bug #16013 from Daryl Waycott.
This is, if memory serves, not the first such bug in the bitstring
functions. In hopes of making it the last one, do a bit more work
than minimally necessary to fix the bug:
* Add assertion checks to bit_out() and varbit_out() to complain if
they are given incorrectly-padded input. This will improve the
odds that manual testing of any new patch finds problems.
* Encapsulate the padding-related logic in macros to make it
easier to use.
Also, remove unnecessary padding logic from bit_or() and bitxor().
Somebody had already noted that we need not re-pad the result of
bit_and() since the inputs are required to be the same length,
but failed to extrapolate that to the other two.
Also, move a comment block that once was near the head of varbit.c
(but people kept putting other stuff in front of it), to put it in
the header block.
Note for the release notes: if anyone has inconsistent data as a
result of saving the output of bitshiftright() in a table, it's
possible to fix it with something like
UPDATE mytab SET bitcol = ~(~bitcol) WHERE bitcol != ~(~bitcol);
This has been broken since day one, so back-patch to all supported
branches.
Discussion: https://postgr.es/m/16013-c2765b6996aacae9@postgresql.org
Up to now, get_const_expr() insisted on prefixing BIT and VARBIT
literals with 'B'. That's not really necessary, because we always
append explicit-cast syntax to identify the constant's type.
Moreover, it's subtly wrong for VARBIT, because the parser will
interpret B'...' as '...'::"bit"; see make_const() which explicitly
assigns type BITOID for a T_BitString literal. So what had been
a simple VARBIT literal is reconstructed as ('...'::"bit")::varbit,
which is not the same thing, at least not before constant folding.
This results in odd differences after dump/restore, as complained
of by the patch submitter, and it could result in actual failures in
partitioning or inheritance DDL operations (see commit 542320c2b,
which repaired similar misbehaviors for some other data types).
Fixing it is pretty easy: just remove the special case and let the
default code path handle these types. We could have kept the special
case for BIT only, but there seems little point in that.
Like the previous patch, I judge that back-patching this into stable
branches wouldn't be a good idea. However, it seems not quite too
late for v11, so let's fix it there.
Paul Guo, reviewed by Davy Machado and John Naylor, minor adjustments
by me
Discussion: https://postgr.es/m/CABQrizdTra=2JEqA6+Ms1D1k1Kqw+aiBBhC9TreuZRX2JzxLAA@mail.gmail.com
and implement OVERLAY() for bit strings and bytea.
In passing also convert text OVERLAY() to a true built-in, instead of
relying on a SQL function.
Leonardo F, reviewed by Kevin Grittner
to do that, but inconsistently.) Make bit type reject too short input,
too, per SQL. Since it no longer zero pads, 'zpbit*' has been renamed to
'bit*' in the source, hence initdb.
Nathan Bossart
Tom Lane
Michael Paquier
Peter Eisentraut
Peter Eisentraut
Thomas G. Lockhart