database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-18 02:02:55 +03:00
Code Activity

Make type Datum be 8 bytes wide everywhere.

Browse Source 
This patch makes sizeof(Datum) be 8 on all platforms including
32-bit ones.  The objective is to allow USE_FLOAT8_BYVAL to be true
everywhere, and in consequence to remove a lot of code that is
specific to pass-by-reference handling of float8, int8, etc.  The
code for abbreviated sort keys can be simplified similarly.  In this
way we can reduce the maintenance effort involved in supporting 32-bit
platforms, without going so far as to actually desupport them.  Since
Datum is strictly an in-memory concept, this has no impact on on-disk
storage, though an initdb or pg_upgrade will be needed to fix affected
catalog entries.

We have required platforms to support [u]int64 for ages, so this
breaks no supported platform.  We can expect that this change will
make 32-bit builds a bit slower and more memory-hungry, although being
able to use pass-by-value handling of 8-byte types may buy back some
of that.  But we stopped optimizing for 32-bit cases a long time ago,
and this seems like just another step on that path.

This initial patch simply forces the correct type definition and
USE_FLOAT8_BYVAL setting, and cleans up a couple of minor compiler
complaints that ensued.  This is sufficient for testing purposes.
In the wake of a bunch of Datum-conversion cleanups by Peter
Eisentraut, this now compiles cleanly with gcc on a 32-bit platform.
(I'd only tested the previous version with clang, which it turns out
is less picky than gcc about width-changing coercions.)

There is a good deal of now-dead code that I'll remove in separate
follow-up patches.

A catversion bump is required because this affects initial catalog
contents (on 32-bit machines) in two ways: pg_type.typbyval changes
for some built-in types, and Const nodes in stored views/rules will
now have 8 bytes not 4 for pass-by-value types.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/1749799.1752797397@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2025-08-13 16:35:06 -04:00
parent 66f8765c53
commit 2a600a93c7
6 changed files with 27 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/storage/ipc/ipc.c
View File

@@ -399,7 +399,7 @@ cancel_before_shmem_exit(pg_on_exit_callback function, Datum arg)
before_shmem_exit_list[before_shmem_exit_index - 1].arg == arg)
--before_shmem_exit_index;
else
elog(ERROR, "before_shmem_exit callback (%p,0x%" PRIxPTR ") is not the latest entry",
elog(ERROR, "before_shmem_exit callback (%p,0x%" PRIx64 ") is not the latest entry",
function, arg);
}

7
src/backend/utils/resowner/resowner.c
View File

@@ -231,11 +231,8 @@ hash_resource_elem(Datum value, const ResourceOwnerDesc *kind)
* 'kind' into the hash. Just add it with hash_combine(), it perturbs the
* result enough for our purposes.
*/
#if SIZEOF_DATUM == 8
return hash_combine64(murmurhash64((uint64) value), (uint64) kind);
#else
return hash_combine(murmurhash32((uint32) value), (uint32) kind);
#endif
return hash_combine64(murmurhash64((uint64) value),
(uint64) (uintptr_t) kind);
}
/*