JingsongLi commented on code in PR #1019:
URL: https://github.com/apache/paimon-rust/pull/1019#discussion_r4176868485
##########
crates/paimon/src/spec/schema.rs:
##########
@@ -584,6 +584,25 @@ impl TableSchema {
})?;
fields[idx] =
fields[idx].clone().with_description(Some(new_comment));
}
+ SchemaChange::UpdateColumnDefaultValue {
+ field_names,
+ new_default_value,
+ } => {
+ let name = top_level_field(&field_names)?;
+ let idx =
+ field_index(&fields, name).ok_or_else(||
crate::Error::ColumnNotExist {
+ full_name: full_name.to_string(),
+ column: name.to_string(),
+ })?;
+ // The default value is recorded on the field as a string
and is
+ // cast/validated where it is consumed (the read path),
exactly as
+ // a default set at create time; this arm only records the
new
+ // spelling. Mirrors Java `SchemaManager` rebuilding the
field with
+ // the new default value.
+ fields[idx] = fields[idx]
Review Comment:
[P2] Validate the new default before publishing the schema
A real FileSystemCatalog Format Table probe changes an INT default from 42
to bad: alter_table returns Ok and advances schema 1 to 2, but the next
new_write fails with Unsupported default value bad, even before input is
written. This handler lets an invalid configuration disable future writes. Java
[SchemaManagerUtils](https://github.com/apache/paimon/blob/master/paimon-core/src/main/java/org/apache/paimon/schema/SchemaManagerUtils.java)
calls validateDefaultValue(field.type(), update.newDefaultValue()) in this
branch before rebuilding the field. Validate against the column type before
applying/persisting the change so a rejected alteration leaves the previous
schema usable.
##########
crates/paimon/src/spec/schema_change.rs:
##########
@@ -80,6 +80,12 @@ pub enum SchemaChange {
field_names: Vec<String>,
new_comment: String,
},
+ /// A SchemaChange to update the field's default value.
+ #[serde(rename_all = "camelCase")]
+ UpdateColumnDefaultValue {
+ field_names: Vec<String>,
+ new_default_value: String,
Review Comment:
[P2] Support Java null defaults when clearing an existing default
The Java-compatible payload
{"action":"updateColumnDefaultValue","fieldNames":["v"],"newDefaultValue":null}
fails Rust deserialization with invalid type: null, expected a string. Java
[DefaultValueUtils](https://github.com/apache/paimon/blob/master/paimon-common/src/main/java/org/apache/paimon/utils/DefaultValueUtils.java)
accepts null, and its schema-change handler passes it to DataField, removing
the existing default. This String field and the unconditional Some in
apply_changes prevent that operation. Model the value as optional and preserve
None through application, with set/clear wire and catalog tests.
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