uros-b commented on code in PR #57564:
URL: https://github.com/apache/spark/pull/57564#discussion_r3657947529
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala:
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@@ -525,6 +535,16 @@ abstract class JdbcDialect extends Serializable with
Logging {
}
}
+ /**
+ * Truncates `expr` toward zero, so that a cast from a fractional type to an
integral type that
+ * is pushed down matches Spark, which truncates rather than rounds.
Dialects for databases that
+ * round such casts override this with the database's truncating function.
The default returns
+ * `expr` unchanged, for databases whose cast already truncates like Spark.
+ * @param expr The SQL string of the value being cast.
+ * @return The SQL string to cast instead of `expr`.
+ */
+ def truncateFractionalValue(expr: String): String = expr
Review Comment:
JdbcDialect is `@DeveloperApi`, so a breaking change is technically
permitted, but the established practice for this trait is to add new hooks as
concrete methods with a safe default (e.g. see getFetchSize,
isSyntaxErrorBestEffort, isObjectNotFoundException,
isNotSelectableObjectException). So yeah, keep the deafult and just add
`@Since("4.3.0")` if you're targeting the last 4.x version (or 5.0.0 if you're
targeting master only).
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