xixipi-lining opened a new pull request, #596:
URL: https://github.com/apache/iceberg-go/pull/596
### Summary
This PR introduces initial schema evolution capabilities, allowing users to
modify table schemas through a fluent API. This work was originally started by
@Shreyas220 in PR #430, but due to time constraints, I'm continuing the
implementation.
### Key Features
- **Add Columns**: Support for adding primitive types, structs, lists, and
maps
- **Delete Columns**: Remove fields from the schema
- **Update Columns**: Modify field properties including name, type,
nullability, and documentation
- **Move Columns**: Reorder fields with operations like `MoveFirst`,
`MoveBefore`, and `MoveAfter`
- **Rename Columns**: Change field names
- **Basic Validation**: Type checking and compatibility validation
### API Usage
```go
// Create a transaction and update schema
txn := table.NewTransaction()
updateSchema := txn.UpdateSchema(true, false) // caseSensitive=true,
allowIncompatibleChanges=false
// Add a new column
updateSchema.AddColumn([]string{"gender"}, iceberg.PrimitiveTypes.String,
"User gender", false, nil)
// Add nested column in struct
updateSchema.AddColumn([]string{"address", "country"},
iceberg.PrimitiveTypes.String, "Country code", false,
iceberg.StringLiteral("US"))
// Add complex nested structure
updateSchema.AddColumn([]string{"profile"}, &iceberg.StructType{
FieldList: []iceberg.NestedField{
{Name: "bio", Type: iceberg.PrimitiveTypes.String, Required: false},
{Name: "avatar", Type: iceberg.PrimitiveTypes.String, Required:
false},
},
}, "User profile", false, nil)
// Add list type
updateSchema.AddColumn([]string{"tags"}, &iceberg.ListType{
Element: iceberg.PrimitiveTypes.String,
ElementRequired: false,
}, "User tags", false, nil)
// Rename a column
updateSchema.RenameColumn([]string{"age"}, "user_age")
// Update column properties
updateSchema.UpdateColumn([]string{"name"}, ColumnUpdate{
Required: iceberg.Optional[bool]{Valid: true, Val: true},
Doc: iceberg.Optional[string]{Valid: true, Val: "User's full name"},
})
// Move column to first position
updateSchema.MoveFirst([]string{"id"})
// Move column before another column
updateSchema.MoveBefore([]string{"name"}, []string{"age"})
// Delete a column
updateSchema.DeleteColumn([]string{"old_field"})
// Chain multiple operations
updateSchema.
AddColumn([]string{"email"}, iceberg.PrimitiveTypes.String, "Email
address", true, nil).
RenameColumn([]string{"phone"}, "phone_number").
MoveAfter([]string{"email"}, []string{"name"}).
DeleteColumn([]string{"deprecated_field"})
// Preview changes without committing
newSchema, err := updateSchema.Apply()
if err != nil {
// Handle validation errors
return err
}
// Commit the changes
err := updateSchema.Commit()
if err != nil {
return err
}
// Commit the entire transaction
updatedTable, err := txn.Commit(ctx)
```
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