aokolnychyi commented on code in PR #50593:
URL: https://github.com/apache/spark/pull/50593#discussion_r2047989560
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/ColumnDefinition.scala:
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@@ -194,17 +194,32 @@ object ColumnDefinition {
/**
* A fake expression to hold the column/variable default value expression and
its original SQL text.
*/
-case class DefaultValueExpression(child: Expression, originalSQL: String)
+case class DefaultValueExpression(
+ child: Expression,
+ originalSQL: String,
+ exposeCurrentDefaultAsExprV2: Boolean)
extends UnaryExpression with Unevaluable {
override def dataType: DataType = child.dataType
+ override def stringArgs: Iterator[Any] = Iterator(child, originalSQL)
override protected def withNewChildInternal(newChild: Expression):
Expression =
copy(child = newChild)
// Convert the default expression to ColumnDefaultValue, which is required
by DS v2 APIs.
def toV2(statement: String, colName: String): ColumnDefaultValue = child
match {
case Literal(value, dataType) =>
- new ColumnDefaultValue(originalSQL, LiteralValue(value, dataType))
+ val literalV2 = LiteralValue(value, dataType)
+ val exprV2 = if (exposeCurrentDefaultAsExprV2) literalV2 else null
+ new ColumnDefaultValue(originalSQL, exprV2, literalV2)
case _ =>
throw QueryCompilationErrors.defaultValueNotConstantError(statement,
colName, originalSQL)
}
}
+
+object DefaultValueExpression {
+ def apply(expr: Expression, originalSQL: String): DefaultValueExpression = {
+ // only expose V2 expressions as current defaults if all Catalyst
expressions are evaluable
+ // Catalyst expressions like CURRENT_USER or CURRENT_DATE will require
special handling
+ val exposeCurrentDefaultAsExprV2 =
!expr.exists(_.isInstanceOf[FoldableUnevaluable])
Review Comment:
I believe `Unevaluable` extends `FoldableUnevaluable`, which is very
confusing. The idea is that we can optimize and squash all expressions as long
as they are not like `CURRENT_USER()`, `CURRENT_CATALOG()`, `NOW`, etc. This is
intentional as we don't want to pass a complicated expression to connectors.
Take a look at the example from tests:
```
sql(
s"""
|CREATE TABLE $tableName (
| id INT,
| salary INT DEFAULT (100 + 23),
| dep STRING DEFAULT ('h' || 'r'),
| active BOOLEAN DEFAULT CAST(1 AS BOOLEAN)
|) USING foo
|""".stripMargin)
```
It is fine to fold these expressions and pass the result literal to the
connector as a write default. If we pass a simplified version of the
expression, there is a higher chance the connector will support that expression.
The following can't be safely squashed into a literal, however:
```
sql(s"CREATE TABLE $tableName (id INT, cat STRING DEFAULT current_catalog())
USING foo")
```
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