OceanBase Database in Oracle mode imposes limitations on expressions of function-based indexes. This topic lists the system functions that are not supported for function-based indexes.
System functions not related to users
System functions not related to users are all prohibited in function-based indexes.
Other system functions
The following system functions are prohibited in function-based indexes.
| AT LOCAL | AT TIME ZONE | CARDINALITY | CHARSET |
| COERCIBILITY | COLLATION | CONNECT_BY_PATH | CURRENT_DATE |
| CURRENT_TIMESTAMP | DBTIMEZONE | DECODE | DEFAULT |
| DUMP | EXTRACT | HOST_IP | IS_SERVING_TENANT |
| LAST_TRACE_ID | LNNVL | LOCALTIMESTAMP | OB_VERSION |
| REGEXP_COUNT | REGEXP_INSTR | REGEXP_LIKE | REGEXP_REPLACE |
| REGEXP_SUBSTR | ROWNUM | RPC_PORT | ROWID_TO_CHAR |
| ROWIDIDTONCHAR | SCN_TO_TIMESTAMP | SESSIONTIMEZONE | SYS_CONTEXT |
| SYS_GUID | SYSDATE | SYSTIMESTAMP | TIMESTAMP_TO_SCN |
| UID | USER | USERENV | VALUES |