cloud-fan commented on code in PR #56238:
URL: https://github.com/apache/spark/pull/56238#discussion_r3338593172
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TableOutputResolver.scala:
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@@ -284,6 +284,31 @@ object TableOutputResolver extends SQLConfHelper with
Logging {
}
}
+ /**
+ * Builds the [[NamedExpression]] for a missing column filled with its
default value, applying a
+ * write-side CHAR/VARCHAR length check so that non-foldable defaults (e.g.
`current_user()`)
+ * that exceed the column length are caught at runtime. Uses `getRawType` so
it works for both
+ * V1 and V2 tables. Shared by the by-name and by-position default-fill
paths.
+ *
+ * `applyColumnMetadata` strips the default's outer alias and re-wraps it
with the required
+ * metadata, so the length check is applied to the default value itself (the
alias child).
Review Comment:
Minor doc-accuracy nit: this sentence attributes the alias unwrap to
`applyColumnMetadata`, but in the CHAR/VARCHAR path the helper itself unwraps
the alias (`case a: Alias => a.child` below) *before* the length check, and
`applyColumnMetadata` then runs on the `StaticInvoke` (no longer an `Alias`),
so it never strips the default's alias here. The unwrap is needed precisely
because otherwise `stringLengthCheck` would wrap the `Alias` and
`applyColumnMetadata` would *not* strip it. Behavior is correct; only the
explanation is backwards. Suggested rewrite:
```suggestion
* We unwrap the default's outer alias before the length check so the
check wraps the
* default value itself, not the alias; `applyColumnMetadata` then re-adds
the required
* alias and metadata afterward.
```
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