xylaaaaa opened a new pull request, #60169:
URL: https://github.com/apache/doris/pull/60169
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
Currently, Doris does not support `ALTER TABLE ... MODIFY COLUMN` for
complex type columns (STRUCT/ARRAY/MAP) in Iceberg external tables. This PR
adds support for safe schema evolution of complex types in Iceberg tables.
**Supported operations:**
| Complex Type | Allowed Operations | Prohibited Operations |
|--------------|-------------------|----------------------|
| STRUCT | Append new fields, safe type promotion for existing fields |
Field rename/delete |
| ARRAY | Element type safe promotion | Incompatible element type change |
| MAP | Value type safe promotion | Key type change |
**Safe type promotions supported in nested types:**
- `INT` → `BIGINT`, `LARGEINT`
- `TINYINT` → `SMALLINT`, `INT`, `BIGINT`, `LARGEINT`
- `SMALLINT` → `INT`, `BIGINT`, `LARGEINT`
- `BIGINT` → `LARGEINT`
- `FLOAT` → `DOUBLE`
- `VARCHAR(n)` → `VARCHAR(m)` where m > n
**Constraints:**
- All new nested fields must be nullable
- Cannot change optional to required
- Complex type default values only support NULL
### Release note
Support ALTER TABLE MODIFY COLUMN for complex types (STRUCT/ARRAY/MAP) in
Iceberg external tables, including appending struct fields and safe type
promotions.
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [x] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
**Manual test steps:**
```sql
-- Create Iceberg table with complex types
CREATE TABLE iceberg_catalog.test_db.iceberg_tbl (
id BIGINT,
user_info STRUCT<name:STRING, scores:ARRAY<INT>, age:INT>,
dt STRING
);
-- Test 1: STRUCT append field (should succeed)
ALTER TABLE iceberg_catalog.test_db.iceberg_tbl
MODIFY COLUMN user_info STRUCT<name:STRING, scores:ARRAY<INT>, age:INT,
email:STRING>;
-- Test 2: STRUCT nested ARRAY element type promotion (should succeed)
ALTER TABLE iceberg_catalog.test_db.iceberg_tbl
MODIFY COLUMN user_info STRUCT<name:STRING, scores:ARRAY<BIGINT>, age:INT,
email:STRING>;
-- Test 3: STRUCT field rename (should fail)
ALTER TABLE iceberg_catalog.test_db.iceberg_tbl
MODIFY COLUMN user_info STRUCT<full_name:STRING, scores:ARRAY<BIGINT>,
age:INT, email:STRING>;
-- Expected error: Cannot rename struct field from 'name' to 'full_name'
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