fix(duckdb)!: LAST_DAY with a WEEK(<day>) part silently returns the last day of the month - #8016
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…st day of the month
_last_day_sql read the unit via expression.text("unit"), which returns ''
for BigQuery's WeekStart node, so LAST_DAY(d, WEEK(SUNDAY)) fell into the
MONTH default and emitted a plain LAST_DAY(d) with no warning, e.g.
2008-11-30 instead of 2008-11-15 for LAST_DAY(DATE '2008-11-10', WEEK(SUNDAY)).
The week branch is generalized to any start day (the old Snowflake
formula is the start-day-Monday case and its output is unchanged), which
also makes ISOWEEK work instead of warning. The generic lastday_sql now
warns for WeekStart units instead of silently dropping them.
georgesittas
requested review from
Copilot,
fivetran-kwoodbeck,
geooo109 and
treysp
July 31, 2026 23:21
Contributor
SQLGlot Integration Test Results✅ All tests passedComparing: Overallmain: 192411 total, 153555 passed (pass rate: 79.8%) sqlglot:jo/duckdb-last-day-week: 188349 total, 150251 passed (pass rate: 79.8%) Transitions: Dialect pair changes: 0 previous results not found, 1 current results not found ✅ All tests passed |
georgesittas
changed the title
geooo109
approved these changes
Aug 3, 2026
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LAST_DAYweek units to DuckDB using the source dialect's week start day,instead of always assuming Monday-start weeks (e.g. BigQuery's
WEEK(SUNDAY),ISOWEEK)WEEKtoWEEK(SUNDAY)at parse time (asDATE_DIFFalready does),so
LAST_DAY(d, WEEK)no longer produces Sunday instead of SaturdayLAST_DAYonly supports months