Description
LEAD returns values from earlier rows instead of NULL when its offset is INT64_MAX and the current row index is greater than zero.
On latest main (234a93f81ce52b4457c7595e455eca4bba3bc680), the window operator computes the source row as:
srcRow := j + int(offset)
if srcRow >= end {
// append default or NULL
} else {
localResult.UnionOne(srcVec, int64(srcRow), ...)
}For offset = math.MaxInt64, j + int(offset) overflows when j > 0. The result becomes negative, bypasses the srcRow >= end check, and is passed to UnionOne. The vector access then silently reads earlier rows.
Reproduction
Equivalent SQL shape:
select id,
lead(id, 9223372036854775807) over (order by id)
from t;With input [10, 20, 30], the operator currently produces null bitmap [0] and physical values [0, 10, 20]: only row 0 is NULL, while rows 1 and 2 incorrectly read prior rows.
Expected behavior
An offset larger than the remaining partition length is out of range for every row, so every LEAD result must be NULL (or the provided default value).
Actual behavior
Rows after the first return data from earlier rows because of signed integer overflow.
Impact
This is silent query-result corruption for a valid BIGINT offset. It does not return an error or panic, so callers can consume incorrect analytical results without noticing.
Description
LEADreturns values from earlier rows instead ofNULLwhen its offset isINT64_MAXand the current row index is greater than zero.On latest
main(234a93f81ce52b4457c7595e455eca4bba3bc680), the window operator computes the source row as:For
offset = math.MaxInt64,j + int(offset)overflows whenj > 0. The result becomes negative, bypasses thesrcRow >= endcheck, and is passed toUnionOne. The vector access then silently reads earlier rows.Reproduction
Equivalent SQL shape:
With input
[10, 20, 30], the operator currently produces null bitmap[0]and physical values[0, 10, 20]: only row 0 is NULL, while rows 1 and 2 incorrectly read prior rows.Expected behavior
An offset larger than the remaining partition length is out of range for every row, so every
LEADresult must beNULL(or the provided default value).Actual behavior
Rows after the first return data from earlier rows because of signed integer overflow.
Impact
This is silent query-result corruption for a valid BIGINT offset. It does not return an error or panic, so callers can consume incorrect analytical results without noticing.