Antalya 26.1 : Fix Alter table operations(add, modify, drop, rename) support for Iceberg#1594
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subkanthi wants to merge 15 commits intoantalya-26.1from
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Antalya 26.1 : Fix Alter table operations(add, modify, drop, rename) support for Iceberg#1594subkanthi wants to merge 15 commits intoantalya-26.1from
subkanthi wants to merge 15 commits intoantalya-26.1from
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subkanthi
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subkanthi
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…d columns to a separate function, added unit tests
subkanthi
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subkanthi
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Apr 2, 2026
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| void assertInitializedDL() const | ||
| { | ||
| BaseStorageConfiguration::assertInitialized(); |
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This was removed in upstream
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Testing: |
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| Poco::JSON::Array::Ptr identifier_fields = new Poco::JSON::Array; | ||
| schema_for_rest->set("identifier-field-ids", identifier_fields); | ||
| } |
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Overwriting identifier-field-ids with an empty array discards any existing row identity configuration for tables created outside ClickHouse. In buildUpdateMetadataRequestBody, schema_for_rest is cloned from the new schema but then unconditionally reset, so an ALTER against a REST-catalog Iceberg table with non-empty identifier fields will silently clear them in the committed schema update. This can break downstream equality-delete/merge workflows that depend on those IDs.
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Addressed, added logic to update identifier-field-ids only if its already set.
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| if (!catalog->updateMetadata(namespace_name, table_name, catalog_filename, metadata)) | ||
| { | ||
| LOG_WARNING(log, "Iceberg alter: catalog update failed for '{}'", catalog_filename); | ||
| continue; | ||
| } |
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After successfully writing the new metadata file, a catalog commit failure currently does continue, which re-enters the loop and applies the same alter operation again on top of already-updated metadata. For ADD COLUMN, this path can produce duplicate field entries (the add generator does not guard against existing names), and for other operations it can cause spurious failures because the first write already changed the schema version. This failure mode is triggered whenever updateMetadata returns false after a successful metadata write (e.g., transient REST error).
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Addressed. If the catalog updateMetadata fails throw an exception.
…, fixed retry logic in Mutations.cpp for catalog updateMetadata
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| Poco::JSON::Object::Ptr cloneJsonObject(const Poco::JSON::Object::Ptr & obj) |
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wow, is this really the best way to clone it? I havent checked th rest of the code yet, but I am curious to understand why this is needed
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ok, I understand why you need it. I also see poco does not offer a deep copy APi, so this is ok
| return result; | ||
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| Poco::JSON::Object::Ptr request_body = new Poco::JSON::Object; |
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I wonder how they (poco lib) manage the life cycle of such objects
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From poco docs Poco::JSON::Object::Ptr is a type alias for a Poco::SharedPtr managing a Poco::JSON::Object .
Its a reference counting smart pointer
| if (!schema_for_rest->has("identifier-field-ids")) | ||
| schema_for_rest->set("identifier-field-ids", new Poco::JSON::Array); | ||
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| if (old_schema_id >= 0) |
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I assume this means: is this not the first schema?
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I honestly dont know he specs, so I cant really give an opinion on the below fields
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yes correct, the logic is const Int32 old_schema_id = new_schema_id - 1; if a current schema exists, then add it to the assert-current-schema-id in the request
{
"identifier": {
"namespace": ["sales", "events"],
"name": "orders"
},
"requirements": [
{ "type": "assert-table-uuid", "uuid": "<table-uuid-from-loadTable>" },
{ "type": "assert-current-schema-id", "current-schema-id": 3 }
],
"updates": [
{
"action": "rename-column",
"name": "old_name",
"new-name": "new_name"
}
]
}
| // "operation" : "replace", | ||
| // "summary" : "replace snapshot 1 with snapshot 2" | ||
| // } | ||
| if (new_snapshot->has("parent-snapshot-id")) |
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Again, I dont know the specs, but to my understand it is impossible that old_schema_id < 0 while parent_snapshot_id != -1. Please educate me
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The else part https://github.com/Altinity/ClickHouse/pull/1594/changes/BASE..4f37d22fc562d75bdad4f41d414125a966520964#diff-a70dee27f63a76254ba9d7e7f9dc632d5cdee3d19be91663d04686247582e6faL1308 is from pre-existing code and is not related to updating schemas, is used for insert/append snapshot. I just moved the code to a separate function as its both related to updating the REST API request.
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Nvm, I confused the if blocks
| request_body->set("updates", updates); | ||
| } | ||
| const auto built = buildUpdateMetadataRequestBody(namespace_name, table_name, new_snapshot); | ||
| if (built.status == UpdateMetadataRequestBodyResult::Status::Skip) |
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Is there a reason to follow this "err as return value" pattern? Usually we just throw exceptions with clear messages and those are propagated back to the user or logged somewhere
| metadata_object->getArray(Iceberg::f_schemas)->add(current_schema); | ||
| } | ||
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| void MetadataGenerator::generateRenameColumnMetadata(const String & column_name, const String & new_column_name) |
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It doesnt look like it generates or outputs anything, I would personally name it differently like set or update
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This is a bugfix of the original upstream PR, kept the same name generateRenameColumnMetadata
void generateAddColumnMetadata(const String & column_name, DataTypePtr type);
void generateDropColumnMetadata(const String & column_name);
void generateModifyColumnMetadata(const String & column_name, DataTypePtr type);
void generateRenameColumnMetadata(const String & column_name, const String & new_column_name);
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This was the original upstream PR https://github.com/ClickHouse/ClickHouse/pull/97455/changes#diff-58d3a6dbeceacc359645fc8bcac193781a4c82ecccfb67a9362db280df353154R339, which implemented these functions, its probably better to keep the function names the same.
| throw Exception(ErrorCodes::BAD_ARGUMENTS, "Iceberg alter supports exactly one command at a time, got {}", params.size()); | ||
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| size_t i = 0; | ||
| while (i++ < MAX_TRANSACTION_RETRIES) |
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I would honestly avoid such unrelated changes, unless we ship it to upstream and then backport
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this is a bug, because i is post-incremented and here it will start with 1.
if (i == MAX_TRANSACTION_RETRIES)
throw Exception(ErrorCodes::LIMIT_EXCEEDED, "Too many unsuccessed retries to alter iceberg table");
| return; | ||
| } | ||
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| bool file_exists = object_storage->exists(StoredObject(storage_metadata_name)); |
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I dont understand why we need two branches, one in case we wrote the hint and one in case we did not
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| if (catalog->updateMetadata(namespace_name, table_name, catalog_filename, metadata)) | ||
| { | ||
| LOG_INFO(log, "Iceberg alter: adopted existing metadata file '{}' and updated catalog", storage_metadata_name); | ||
| return; |
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When writeMetadataFileAndVersionHint fails because the target file already exists, this branch returns success as soon as catalog->updateMetadata(...) succeeds. For Glue catalogs, GlueCatalog::updateMetadata (see src/Databases/DataLake/GlueCatalog.cpp) only repoints metadata_location and does not validate that the existing file contains this ALTER’s schema changes, so a concurrent writer’s file can be "adopted" and the user gets a successful ALTER that was never applied.
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| if (!catalog->updateMetadata(namespace_name, table_name, catalog_filename, metadata)) | ||
| { | ||
| throw Exception( | ||
| ErrorCodes::DATALAKE_DATABASE_ERROR, | ||
| "Iceberg alter: catalog commit failed for '{}' after metadata file was written successfully", |
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A failed catalog->updateMetadata(...) immediately throws and exits the transaction loop, so MAX_TRANSACTION_RETRIES is effectively skipped for catalog conflicts/transient failures after metadata write. In practice, concurrent schema updates (e.g. REST commit conflict responses) will fail on first conflict instead of retrying from fresh metadata, unlike the mutation path’s retry behavior.
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Apr 22, 2026
…ter post-write branches Addresses review feedback on PR #1594: R1480: replace err-as-return-value pattern in buildUpdateMetadataRequestBody with standard exception/null semantics. - Return nullptr for the "no snapshot, nothing to commit" skip case. - Throw DB::Exception(DATALAKE_DATABASE_ERROR) with a specific message for malformed metadata (missing current-schema-id, no schema object matching current-schema-id). - RestCatalog::updateMetadata keeps its bool return for ICatalog compatibility but now logs the full HTTPException displayText on commit failure instead of silently swallowing it. - Drop UpdateMetadataRequestBodyResult struct; callers consume the Poco::JSON::Object::Ptr directly. - Update gtest_rest_catalog_update_metadata: use EXPECT_FALSE(body) for skip, EXPECT_THROW(..., DB::Exception) for malformed inputs, ASSERT_TRUE(body) for success, and assert on the requirements/updates payload shape. R768: collapse the two-branch post-write logic in Mutations.cpp alter retry loop into a single flow driven by wrote_ok and file_exists: - wrote_ok=true -> commit to catalog, fatal if catalog rejects. - wrote_ok=false && file_exists -> orphan-adopt: attempt catalog commit; on failure continue to next retry (do not throw). - wrote_ok=false && !file_exists -> retry with a new version. Adds a comment explaining why orphan-adopt is preferred over writing a new version. Made-with: Cursor
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… code. Signed-off-by: Kanthi Subramanian <subkanthi@gmail.com>
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arthurpassos
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Left some comment. Otherwise lgtm
| compression_method, | ||
| data_lake_settings[DataLakeStorageSetting::iceberg_use_version_hint]); | ||
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| // If the write helper reported failure but the metadata file nonetheless landed on |
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Are you sure this is a good idea? What if it indeed failed to write, but some other writer shipped a file with the same name? If the filenames contain some sort of UUID, then it is ok.
But I actually don't understand why you need to go this far. If you didn't get a response, ins't it easier to just fail the operation and retry?
| // "operation" : "replace", | ||
| // "summary" : "replace snapshot 1 with snapshot 2" | ||
| // } | ||
| if (new_snapshot->has("parent-snapshot-id")) |
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Nvm, I confused the if blocks
| catalog_filename); | ||
| continue; | ||
| } | ||
| if (!wrote_ok) |
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Should you even consider updating the catalog if you failed to write the metadata file?
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| void StorageObjectStorage::alter(const AlterCommands & params, ContextPtr context, AlterLockHolder & /*alter_lock_holder*/) | ||
| { | ||
| configuration->update(object_storage, context, /* if_not_updated_before */ true); |
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Shouldn't it be like this?
if (update_configuration_on_read_write)
{
configuration->update(
object_storage,
local_context,
/* if_not_updated_before */ false);
}
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Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Fixes Alter table ADD/DROP/RENAME/MODIFY column for Iceberg tables.
Documentation entry for user-facing changes
Solved ClickHouse#86024.
Fixed logic of updating metadata JSON as per Iceberg REST API Spec.
Added unit/integration tests.
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