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Eliminate possible race between ALTER_METADATA and MERGE_PARTS

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v2: move metadata version check after checking that the part is not covering part
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
This commit is contained in:
Azat Khuzhin 2023-12-11 17:47:22 +01:00
parent 7efe413575
commit a12df35be4
3 changed files with 16 additions and 7 deletions
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16
src/Storages/MergeTree/MergeFromLogEntryTask.cpp
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@ -43,6 +43,8 @@ ReplicatedMergeMutateTaskBase::PrepareResult MergeFromLogEntryTask::prepare()
LOG_TRACE(log, "Executing log entry to merge parts {} to {}",
fmt::join(entry.source_parts, ", "), entry.new_part_name);
StorageMetadataPtr metadata_snapshot = storage.getInMemoryMetadataPtr();
int32_t metadata_version = metadata_snapshot->getMetadataVersion();
const auto storage_settings_ptr = storage.getSettings();
if (storage_settings_ptr->always_fetch_merged_part)
@ -129,6 +131,18 @@ ReplicatedMergeMutateTaskBase::PrepareResult MergeFromLogEntryTask::prepare()
};
}
int32_t part_metadata_version = source_part_or_covering->getMetadataVersion();
if (part_metadata_version > metadata_version)
{
LOG_DEBUG(log, "Source part metadata version {} is newer then the table metadata version {}. ALTER_METADATA is still in progress.",
part_metadata_version, metadata_version);
return PrepareResult{
.prepared_successfully = false,
.need_to_check_missing_part_in_fetch = false,
.part_log_writer = {}
};
}
parts.push_back(source_part_or_covering);
}
@ -176,8 +190,6 @@ ReplicatedMergeMutateTaskBase::PrepareResult MergeFromLogEntryTask::prepare()
/// It will live until the whole task is being destroyed
table_lock_holder = storage.lockForShare(RWLockImpl::NO_QUERY, storage_settings_ptr->lock_acquire_timeout_for_background_operations);
StorageMetadataPtr metadata_snapshot = storage.getInMemoryMetadataPtr();
auto future_merged_part = std::make_shared<FutureMergedMutatedPart>(parts, entry.new_part_format);
if (future_merged_part->name != entry.new_part_name)
{

6
src/Storages/StorageReplicatedMergeTree.cpp
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@ -1745,14 +1745,12 @@ bool StorageReplicatedMergeTree::checkPartChecksumsAndAddCommitOps(
if (replica_part_header.getColumnsHash() != local_part_header.getColumnsHash())
{
/// Currently there are two (known) cases when it may happen:
/// Currently there are only one (known) cases when it may happen:
/// - KILL MUTATION query had removed mutation before all replicas have executed assigned MUTATE_PART entries.
/// Some replicas may skip this mutation and update part version without actually applying any changes.
/// It leads to mismatching checksum if changes were applied on other replicas.
/// - ALTER_METADATA and MERGE_PARTS were reordered on some replicas.
/// It may lead to different number of columns in merged parts on these replicas.
throw Exception(ErrorCodes::CHECKSUM_DOESNT_MATCH, "Part {} from {} has different columns hash "
"(it may rarely happen on race condition with KILL MUTATION or ALTER COLUMN).", part_name, replica);
"(it may rarely happen on race condition with KILL MUTATION).", part_name, replica);
}
replica_part_header.getChecksums().checkEqual(local_part_header.getChecksums(), true);

1
tests/queries/0_stateless/02943_rmt_alter_metadata_merge_checksum_mismatch.reference
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@ -1 +0,0 @@
all_0_2_2_1 RegularMerge MergeParts CHECKSUM_DOESNT_MATCH