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use crate::catalog::table::Column;
use crate::diff::operations::ColumnAction;
/// Diff a single column
pub fn diff(old: Option<&Column>, new: Option<&Column>) -> Vec<ColumnAction> {
match (old, new) {
// 1) brand-new column
(None, Some(n)) => {
vec![ColumnAction::Add { column: n.clone() }]
}
// 2) dropped column
(Some(o), None) => {
vec![ColumnAction::Drop {
name: o.name.clone(),
}]
}
// 3) existed in both → type, default, or not null changed?
(Some(o), Some(n)) => {
let mut changes = Vec::new();
if o.data_type != n.data_type {
changes.push(ColumnAction::AlterType {
name: n.name.clone(),
new_type: n.data_type.clone(),
});
}
if o.generated != n.generated {
match (&o.generated, &n.generated) {
(Some(_), None) => {
changes.push(ColumnAction::DropGenerated {
name: n.name.clone(),
});
}
(None, Some(_)) => {
changes.push(ColumnAction::Drop {
name: n.name.clone(),
});
changes.extend(diff(None, Some(n)));
}
(Some(old_expr), Some(new_expr)) if old_expr != new_expr => {
changes.push(ColumnAction::Drop {
name: n.name.clone(),
});
changes.extend(diff(None, Some(n)));
}
_ => {}
}
}
// Check for changes in IDENTITY
match (o.identity, n.identity) {
(None, Some(kind)) => {
changes.push(ColumnAction::AddIdentity {
name: n.name.clone(),
kind,
});
}
(Some(_), None) => {
changes.push(ColumnAction::DropIdentity {
name: n.name.clone(),
});
}
(Some(old_kind), Some(new_kind)) if old_kind != new_kind => {
changes.push(ColumnAction::SetIdentityKind {
name: n.name.clone(),
kind: new_kind,
});
}
_ => {}
}
// Check for changes in DEFAULT
match (&o.default, &n.default) {
(Some(_), None) => {
changes.push(ColumnAction::DropDefault {
name: n.name.clone(),
});
}
(None, Some(d)) => {
changes.push(ColumnAction::SetDefault {
name: n.name.clone(),
default: d.clone(),
});
}
_ => {}
}
// Check for changes in NOT NULL constraint
match (o.not_null, n.not_null) {
(false, true) => {
changes.push(ColumnAction::SetNotNull {
name: n.name.clone(),
});
}
(true, false) => {
changes.push(ColumnAction::DropNotNull {
name: n.name.clone(),
});
}
_ => {}
}
// Note: Column comments are handled separately in the table diff
// since they require schema/table context for the CommentOperation
changes
}
// (None, None) impossible
_ => Vec::new(),
}
}