Peter Geoghegan 7c365eb504 Make handling of redundant nbtree keys more robust. ... nbtree preprocessing's handling of redundant (and contradictory) keys created problems for scans with = arrays. It was just about possible for a scan with an = array key and one or more redundant keys (keys that preprocessing could not eliminate due an incomplete opfamily and a cross-type key) to get stuck. Testing has shown that infinite cycling where the scan never manages to make forward progress was possible. This could happen when the scan's arrays were reset in _bt_readpage's forcenonrequired=true path (added by bugfix commit 5f4d98d4) when the arrays weren't at least advanced up to the same point that they were in at the start of the _bt_readpage call. Earlier redundant keys prevented the finaltup call to _bt_advance_array_keys from reaching lower-order keys that needed to be used to sufficiently advance the scan's arrays. To fix, make preprocessing leave the scan's keys in a state that is as close as possible to how it'll usually leave them (in the common case where there's no redundant keys that preprocessing failed to eliminate). Now nbtree preprocessing _reliably_ leaves behind at most one required >/>= key per index column, and at most one required </<= key per index column. Columns that have one or more = keys that are eligible to be marked required (based on the traditional rules) prioritize the = keys over redundant inequality keys; they'll _reliably_ be left with only one of the = keys as the index column's only required key. Keys that are not marked required (whether due to the new preprocessing step running or for some other reason) are relocated to the end of the so->keyData[] array as needed. That way they'll always be evaluated after the scan's required keys, and so cannot prevent code in places like _bt_advance_array_keys and _bt_first from reaching a required key. Also teach _bt_first to decide which initial positioning keys to use based on the same requiredness markings that have long been used by _bt_checkkeys/_bt_advance_array_keys. This is a necessary condition for reliably avoiding infinite cycling. _bt_advance_array_keys expects to be able to reason about what'll happen in the next _bt_first call should it start another primitive index scan, by evaluating inequality keys that were marked required in the opposite-to-scan scan direction only. Now everybody (_bt_first, _bt_checkkeys, and _bt_advance_array_keys) will always agree on which exact key will be used on each index column to start and/or end the scan (except when row compare keys are involved, which have similar problems not addressed by this commit). An upcoming commit will finish off the work started by this commit by harmonizing how _bt_first, _bt_checkkeys, and _bt_advance_array_keys apply row compare keys to start and end scans. This fixes what was arguably an oversight in either commit 5f4d98d4 or commit 8a510275. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Heikki Linnakangas <heikki.linnakangas@iki.fi> Discussion: https://postgr.es/m/CAH2-Wz=ds4M+3NXMgwxYxqU8MULaLf696_v5g=9WNmWL2=Uo2A@mail.gmail.com Backpatch-through: 18		2025-07-02 09:40:48 -04:00
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backend	Make handling of redundant nbtree keys more robust.	2025-07-02 09:40:48 -04:00
bin	Fix bug in archive streamer with LZ4 decompression	2025-07-02 13:48:41 +09:00
common	Use 'void *' for arbitrary buffers, 'uint8 *' for byte arrays	2025-05-08 22:01:25 +03:00
fe_utils	Fix bug in archive streamer with LZ4 decompression	2025-07-02 13:48:41 +09:00
include	Remove implicit cast from 'void *'	2025-07-02 11:51:53 +07:00
interfaces	libpq: Message style improvements	2025-06-26 22:13:53 +02:00
makefiles	pgxs.mk: remove unreachable rule for deleting regress.def.	2025-06-20 12:12:29 -04:00
pl	Sync typedefs.list with the buildfarm.	2025-06-15 13:04:24 -04:00
port	Fix indentation in pg_numa code	2025-07-01 15:24:19 +02:00
template	thread-safety: gmtime_r(), localtime_r()	2024-08-23 07:43:04 +02:00
test	Run pgperltidy	2025-06-29 21:14:21 -04:00
timezone	Update time zone data files to tzdata release 2025b.	2025-04-30 11:13:49 -04:00
tools	Silence valgrind about pg_numa_touch_mem_if_required	2025-07-01 12:33:29 +02:00
tutorial	Doc: simplify the tutorial's window-function examples.	2025-01-21 14:43:21 -05:00
.gitignore
DEVELOPERS
Makefile	Remove distprep	2023-11-06 15:18:04 +01:00
Makefile.global.in	oauth: Move the builtin flow into a separate module	2025-05-01 09:14:30 -07:00
Makefile.shlib	Use exported symbols list on macOS for loadable modules as well	2025-06-10 07:04:43 +02:00
meson.build	Update copyright for 2025	2025-01-01 11:21:55 -05:00
nls-global.mk	Remove distprep	2023-11-06 15:18:04 +01:00