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[fix](wal) Fix WAL replay loading 0 rows due to columns being marked as missing #62658

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Merged
hello-stephen merged 1 commit into from
Apr 21, 2026
+12 −4
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[fix](wal) Fix WAL replay loading 0 rows due to columns being marked as missing #62658

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16 changes: 12 additions & 4 deletions be/src/load/group_commit/wal/wal_reader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,16 +41,16 @@ Status WalReader::init_reader(const TupleDescriptor* tuple_descriptor) {

// ---- Unified init_reader(ReaderInitContext*) overrides ----

Status WalReader::_open_file_reader(ReaderInitContext* /*ctx*/) {
Status WalReader::_open_file_reader(ReaderInitContext* ctx) {
auto* wal_ctx = checked_context_cast<WalInitContext>(ctx);
_tuple_descriptor = wal_ctx->output_tuple_descriptor;
Comment on lines +44 to +46
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Copilot AI Apr 21, 2026

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wal_ctx->output_tuple_descriptor is dereferenced later via _tuple_descriptor->slots() (both in _do_get_next_block and in _get_columns_impl). If it is ever null, this will crash and/or silently reintroduce the “all columns missing” behavior. Please add an explicit validation here (return an error Status with a clear message) instead of relying on implicit invariants.

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RETURN_IF_ERROR(_state->exec_env()->wal_mgr()->get_wal_path(_wal_id, _wal_path));
_wal_reader = std::make_shared<doris::WalFileReader>(_wal_path);
RETURN_IF_ERROR(_wal_reader->init());
return Status::OK();
}

Status WalReader::_do_init_reader(ReaderInitContext* base_ctx) {
auto* ctx = checked_context_cast<WalInitContext>(base_ctx);
_tuple_descriptor = ctx->output_tuple_descriptor;
Status WalReader::_do_init_reader(ReaderInitContext* /*base_ctx*/) {
return Status::OK();
}

Expand Down Expand Up @@ -131,6 +131,14 @@ Status WalReader::_get_columns_impl(std::unordered_map<std::string, DataTypePtr>
} catch (const std::invalid_argument& e) {
return Status::InvalidArgument("Invalid format, {}", e.what());
}
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Please add a regression test for this path. This patch fixes the on_before_init_reader() / get_columns() ordering bug, but the nearby scanner-based WAL tests in be/test/format/wal/wal_manager_test.cpp are currently disabled, and this PR does not add replacement coverage. Without a FileScanner + FORMAT_WAL test (or equivalent replay coverage), this exact all columns marked missing -> replay writes NULL/defaults regression can slip back in unnoticed.

// Report WAL columns so on_before_init_reader does not mark them as missing.
if (_tuple_descriptor) {
for (auto* slot_desc : _tuple_descriptor->slots()) {
if (_column_pos_map.contains(slot_desc->col_unique_id())) {
name_to_type->emplace(slot_desc->col_name(), slot_desc->get_data_type_ptr());
}
}
}
Comment on lines +134 to +141
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Copilot AI Apr 21, 2026

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This change alters how WAL schema is reported to TableFormatReader::on_before_init_reader() (via _get_columns_impl), which was previously causing runtime “missing column” behavior. Please add/enable a unit/regression test that reproduces the 0-rows WAL replay issue and asserts the reader no longer marks present WAL columns as missing (e.g., via missing_cols() or by verifying the output block row count is preserved).

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return Status::OK();
}

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