feat(snowflake)!: updates for Snowflake to DuckDB transpilation of TO_TIMESTAMP functions

[fivetran-kwoodbeck]

This fixes a variety of issues in transpilation of Snowflake's TO_TIMESTAMP and TRY_TO_TIMESTAMP family of functions to DuckDB, fixing several edge cases and adding support for missing variants.

Snowflake Parser (snowflake.py)

• Added TRY_TO_TIMESTAMP_LTZ/NTZ/TZ parser mappings for safe timestamp conversion variants
• Fixed numeric-looking strings with format: TO_TIMESTAMP('20240115103045', 'YYYYMMDDHH24MISS') was incorrectly parsed as unix timestamp instead of using the format string
• Fixed negative unix timestamps: Added exp.Neg handling so TO_TIMESTAMP(-86400) parses correctly
• Added missing AM/PM format mapping: AM/PM → %p in TIME_MAPPING for 12-hour time parsing
• Added target_type tracking: UnixToTime and StrToTime expressions now track the target timestamp type (TIMESTAMP, TIMESTAMPLTZ, TIMESTAMPNTZ, TIMESTAMPTZ)

DuckDB Generator (duckdb.py)

• Fixed NTZ timezone handling: DuckDB's TO_TIMESTAMP(n) returns TIMESTAMPTZ, but Snowflake's returns TIMESTAMP (NTZ interpreted as UTC). Now uses AT TIME ZONE 'UTC' to extract UTC time as naive timestamp
• Added TIMESTAMPLTZ type mapping: Maps to TIMESTAMPTZ in DuckDB
• Fixed LTZ/TZ format string handling: strtotime_sql now casts to TIMESTAMPTZ for LTZ/TZ variants (both TRY and non-TRY)

Expressions (expressions.py)

• Added target_type to UnixToTime.arg_types to track desired output type

Test Queries

Note: See the Jira ticket for the full suite of tests.

Snowflake	DuckDB
TO_TIMESTAMP(1704067200)	TO_TIMESTAMP(1704067200) AT TIME ZONE 'UTC'
TO_TIMESTAMP('20240115', 'YYYYMMDD')	STRPTIME('20240115', '%Y%m%d')
TO_TIMESTAMP('10:30 PM', 'HH12:MI AM')	STRPTIME('10:30 PM', '%I:%M %p')
TRY_TO_TIMESTAMP_LTZ('2024-01-15')	TRY_CAST('2024-01-15' AS TIMESTAMPTZ)
TO_TIMESTAMP_LTZ('...', 'fmt')	CAST(STRPTIME('...', '%fmt') AS TIMESTAMPTZ)

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:feature/transpile-to_timestamp, sqlglot version: feature/transpile-to_timestamp)
• baseline (main, sqlglot version: 28.5.1.dev45)

⚠️ Limited to dialects: duckdb, snowflake

By Dialect

dialect	main	sqlglot:feature/transpile-to_timestamp	difference	links
duckdb -> duckdb	4003/4003 passed (100.0%)	4003/4003 passed (100.0%)	No change	full result / delta
snowflake -> duckdb	626/1085 passed (57.7%)	628/1085 passed (57.9%)	⬆ improved by 0.2%	full result / delta
snowflake -> snowflake	981/1085 passed (90.4%)	981/1085 passed (90.4%)	No change	full result / delta

Overall

main: 6173 total, 5610 passed (pass rate: 90.9%), sqlglot version: 28.5.1.dev45

sqlglot:feature/transpile-to_timestamp: 6173 total, 5612 passed (pass rate: 90.9%), sqlglot version: feature/transpile-to_timestamp

Difference: No change

[VaggelisD]

Nice work @fivetran-kwoodbeck! Leaving a few comments from my first pass: