cloud-fan commented on a change in pull request #26806: [SPARK-30183][SQL]
Disallow to specify reserved properties in CREATE NAMESPACE syntax
URL: https://github.com/apache/spark/pull/26806#discussion_r363833688
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File path: docs/sql-migration-guide.md
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@@ -264,6 +264,8 @@ license: |
- Since Spark 3.0, the function `percentile_approx` and its alias
`approx_percentile` only accept integral value with range in `[1, 2147483647]`
as its 3rd argument `accuracy`, fractional and string types are disallowed,
e.g. `percentile_approx(10.0, 0.2, 1.8D)` will cause `AnalysisException`. In
Spark version 2.4 and earlier, if `accuracy` is fractional or string value, it
will be coerced to an int value, `percentile_approx(10.0, 0.2, 1.8D)` is
operated as `percentile_approx(10.0, 0.2, 1)` which results in `10.0`.
+ - Since Spark 3.0, the words `location` and `comment` become reserved
database properties, it will fail with `ParseException` if we use them as
members of `DBPROTERTIES` in `CREATE DATABASE` and `ALTER DATABASE ... SET
PROPERTIES(...)`. We need their specific clauses to specify them, e.g. `CREATE
DATABASE test COMMENT 'any comment' LOCATION 'some path'`. We can set
`spark.sql.legacy.property.nonReserved` to `true` to ignore the
`ParseException`, in this case, these properties will be silently removed, e.g
`SET DBPROTERTIES('location'='/tmp')` will affect nothing. In Spark version 2.4
and earlier, these properties are neither reserved nor have side effects, e.g.
`SET DBPROTERTIES('location'='/tmp')` will not change the location of the
database but only create a headless property just like `'a'='b'`.
Review comment:
nit:
```
Since Spark 3.0, `location` and `comment` become reserved database
properties. Commands
will fail if we specify reserved properties in `CREATE DATABASE ...
DBPROTERTIES ` and
`ALTER DATABASE ... SET PROPERTIES`. ...
```
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