pgsql: Fix integer overflow in array_agg(), when the array grows too la

Fix integer overflow in array_agg(), when the array grows too large

If you accumulate many arrays full of NULLs, you could overflow
'nitems', before reaching the MaxAllocSize limit on the allocations.
Add an explicit check that the number of items doesn't grow too large.
With more than MaxArraySize items, getting the final result with
makeArrayResultArr() would fail anyway, so better to error out early.

Reported-by: Xint Code
Author: Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Backpatch-through: 14
Security: CVE-2026-6473

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/8e81995de30c5a1834d7dae56a6396067d491975
Author: Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>

Modified Files
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src/backend/utils/adt/arrayfuncs.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)