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schema_tables: turn view schema fixing code into a sanity check

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The purpose of `maybe_fix_legacy_secondary_index_mv_schema` was to deal
with legacy materialized view schemas used for secondary indexes,
schemas which were created before the notion of "computed columns" was
introduced. Back then, secondary index schemas would use a regular
"token" column. Later it became a computed column and old schemas would
be migrated during rolling upgrade.

The migration code was introduced in 2019
(db8d4a0cc6) and then fixed in 2020
(d473bc9b06).

The fix was present in Enterprise 2022.1 and in OSS 4.5. So, assuming
that users don't try crazy things like upgrading from 2021.X to 2023.X
(which we do not support), all clusters will have already executed the
migration code once they upgrade to 2023.X, meaning we can get rid of
it.

The main motivation of this patch is to get rid of the
`db::schema_tables::merge_schema` call in `parse_schema_tables`. In Raft
mode this was the only call to `merge_schema` outside "group 0 code" and
in fact it is unsafe -- it uses locally generated mutations with locally
generated timestamp (`api::new_timestamp()`), so if we actually did it,
we would permanently diverge the group 0 state machine across nodes
(the schema pulling code is disabled in Raft mode). Fortunately, this
should be dead code by now, as explained in the previous paragraph.

The migration code is now turned into a sanity check, if the users
try something crazy, they will get an error instead of silent data
corruption.
This commit is contained in:
Kamil Braun
2023-10-11 14:48:23 +02:00
parent f02ac9a9e7
commit 3976808b12
6 changed files with 37 additions and 65 deletions
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24
db/view/view.cc
View File

@@ -575,7 +575,6 @@ private:
const partition_key& _base_key;
const clustering_or_static_row& _update;
const std::optional<clustering_or_static_row>& _existing;
const bool _backing_secondary_index;
public:
value_getter(const schema& base, const partition_key& base_key, const clustering_or_static_row& update, const std::optional<clustering_or_static_row>& existing, bool backing_secondary_index)
@@ -583,7 +582,6 @@ public:
, _base_key(base_key)
, _update(update)
, _existing(existing)
, _backing_secondary_index(backing_secondary_index)
{
}
@@ -616,22 +614,18 @@ public:
private:
vector_type handle_computed_column(const column_definition& cdef) {
bytes computed_value;
if (!cdef.is_computed()) {
//FIXME(sarna): this legacy code is here for backward compatibility and should be removed
// once "computed_columns feature" is supported by every node
if (!_backing_secondary_index) {
throw std::logic_error(format("Column {} doesn't exist in base and this view is not backing a secondary index", cdef.name_as_text()));
}
computed_value = legacy_token_column_computation().compute_value(_base, _base_key);
} else {
auto& computation = cdef.get_computation();
if (auto* collection_computation = dynamic_cast<const collection_column_computation*>(&computation)) {
return handle_collection_column_computation(collection_computation);
}
computed_value = computation.compute_value(_base, _base_key);
throw std::logic_error{format(
"Detected legacy non-computed token column {} in view for table {}.{}",
cdef.name_as_text(), _base.ks_name(), _base.cf_name())};
}
auto& computation = cdef.get_computation();
if (auto* collection_computation = dynamic_cast<const collection_column_computation*>(&computation)) {
return handle_collection_column_computation(collection_computation);
}
auto computed_value = computation.compute_value(_base, _base_key);
return {managed_bytes_view(linearized_values.emplace_back(std::move(computed_value)))};
}