IndexFunction:
| "LOWER"
| "UPPER"
| "TRIM"
| "LTRIM"
| "RTRIM"
| "SUBSTRING"
| "SUBSTR"
| "LENGTH"
| "CONCAT"
| "COALESCE"
| "NULLIF"
| "ABS"
| "CEIL"
| "FLOOR"
| "ROUND"
| "SQRT"
| "POWER"
| "MOD"
| "NOW"
| "CURRENT_DATE"
| "CURRENT_TIME"
| "CURRENT_TIMESTAMP"
| "DATE"
| "TIME"
| "YEAR"
| "MONTH"
| "DAY"
| "HOUR"
| "MINUTE"
| "SECOND"
| "EXTRACT"
| "TO_CHAR"
| "TO_DATE"
| "TO_TIMESTAMP"
| "JSON_EXTRACT"
| "JSONB_EXTRACT"
| "CAST"
| "CONVERT"
Supported SQL functions for index expressions