feat(duckdb)!: Add transpilation support for DATE_DIFF function

[fivetran-amrutabhimsenayachit]

The WEEK unit in DATEDIFF produces different results between Snowflake and DuckDB due to fundamentally different calculation methodologies:

Snowflake: Counts the number of week boundaries crossed.

DuckDB: Performs floor(days_diff / 7) - integer division.

TRANSPILATION:
python3 -c "import sqlglot; print(sqlglot.transpile(\"SELECT DATEDIFF(WEEK, '2020-01-15', '2023-06-20') AS diff_weeks, DATEDIFF(WEEK, '2024-12-13', '2024-12-17') AS week_monday_cross, DATEDIFF(WEEK, '2024-12-15', '2024-12-16') AS week_same_week\", read='snowflake', write='duckdb')[0])"
SELECT DATE_DIFF('WEEK', CAST('2020-01-15' AS DATE), CAST('2023-06-20' AS DATE)) AS diff_weeks, DATE_DIFF('WEEK', CAST('2024-12-13' AS DATE), CAST('2024-12-17' AS DATE)) AS week_monday_cross, DATE_DIFF('WEEK', CAST('2024-12-15' AS DATE), CAST('2024-12-16' AS DATE)) AS week_same_week

DUCKDB:
duckdb -c "SELECT DATE_DIFF('WEEK', CAST('2020-01-15' AS DATE), CAST('2023-06-20' AS DATE)) AS diff_weeks, DATE_DIFF('WEEK', CAST('2024-12-13' AS DATE), CAST('2024-12-17' AS DATE)) AS week_monday_cross, DATE_DIFF('WEEK', CAST('2024-12-15' AS DATE), CAST('2024-12-16' AS DATE)) AS week_same_week"
┌────────────┬───────────────────┬────────────────┐
│ diff_weeks │ week_monday_cross │ week_same_week │
│   int64    │       int64       │     int64      │
├────────────┼───────────────────┼────────────────┤
│    178     │         0         │       0        │
└────────────┴───────────────────┴────────────────┘

To fix this, enable date_part_boundary for Snowflake DATEDIFF.

TRANSPILATION:
python3 -c "import sqlglot; print(sqlglot.transpile(\"SELECT DATEDIFF(WEEK, '2020-01-15', '2023-06-20') AS diff_weeks, DATEDIFF(WEEK, '2024-12-13', '2024-12-17') AS week_monday_cross, DATEDIFF(WEEK, '2024-12-15', '2024-12-16') AS week_same_week\", read='snowflake', write='duckdb')[0])"

SELECT DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2020-01-15' AS DATE)), DATE_TRUNC('WEEK', CAST('2023-06-20' AS DATE))) AS diff_weeks, DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2024-12-13' AS DATE)), DATE_TRUNC('WEEK', CAST('2024-12-17' AS DATE))) AS week_monday_cross, DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2024-12-15' AS DATE)), DATE_TRUNC('WEEK', CAST('2024-12-16' AS DATE))) AS week_same_week

DUCKDB:
"SELECT DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2020-01-15' AS DATE)), DATE_TRUNC('WEEK', CAST('2023-06-20' AS DATE))) AS diff_weeks, DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2024-12-13' AS DATE)), DATE_TRUNC('WEEK', CAST('2024-12-17' AS DATE))) AS week_monday_cross, DATE_DIFF('WEEK', DATE_TRUNC('WEEK', CAST('2024-12-15' AS DATE)), DATE_TRUNC('WEEK', CAST('2024-12-16' AS DATE))) AS week_same_week"
┌────────────┬───────────────────┬────────────────┐
│ diff_weeks │ week_monday_cross │ week_same_week │
│   int64    │       int64       │     int64      │
├────────────┼───────────────────┼────────────────┤
│    179     │         1         │       1        │
└────────────┴───────────────────┴────────────────┘

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:RD-1069363-datediff, sqlglot version: RD-1069363-datediff)
• baseline (main, sqlglot version: 28.5.1.dev15)

⚠️ Limited to dialects: snowflake

By Dialect

dialect	main	sqlglot:RD-1069363-datediff	difference	links
snowflake -> duckdb	622/1085 passed (57.3%)	624/1085 passed (57.5%)	⬆ improved by 0.2%	full result / delta
snowflake -> snowflake	975/1085 passed (89.9%)	975/1085 passed (89.9%)	No change	full result / delta

Overall

main: 2170 total, 1597 passed (pass rate: 73.6%), sqlglot version: 28.5.1.dev15

sqlglot:RD-1069363-datediff: 2170 total, 1599 passed (pass rate: 73.7%), sqlglot version: RD-1069363-datediff

Difference: ⬆ improved by 0.1%