Github user dongjoon-hyun commented on the issue:
https://github.com/apache/spark/pull/14086
Now, the PR have a ability to allow `truncate` option only if `TRUNCATE
TABLE` default is not cascading. For the unknown or
known-to-be-cascading-default DBMS (Postgres), `truncate` option is ignored.
Spark Dialects | CASCADING TRUNCATE DEFAULT | `truncate` OPTION SUPPORT
---------------|-----------------------------------|-------------------------------
MySQLDialect | X | O
PostgresDialect | O | X
DB2Dialect | X | O
MsSqlServerDialect | X | O
DerbyDialect | X | O
OracleDialect | X | O
H2Dialect | X | O
During searching, I found this [DBMS
Comparison](http://www.sql-workbench.net/dbms_comparison.html) (Last updated:
2016-05-16)
It looks consistent with each DBMS's docs. Please note that the approach of
this PR gives two steps of choice for users.
- First step, users can choose `truncate` option for their own risk.
- Second step, although the `truncate` option is true, we do not use
`TRUNCATE TABLE` for unknown DBMSs or known-to-be-different DBMS.
Always, the fallback operation is the existing `DROP TABLE`.
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