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schema_tables: refactor scylla_tables(schema_features)

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The `scylla_tables` function gives a different schema definition
for the `system_schema.scylla_tables` table, depending on whether
certain schema features are enabled or not.

The way it was implemented, we had to write `θ(2^n)` amount
of code and comments to handle `n` features.

Refactor it so that the amount of code we have to write to handle `n`
features is `θ(n)`.
This commit is contained in:
Kamil Braun
2023-09-07 13:25:00 +02:00
parent 2d561eecbc
commit dc4e20d835
1 changed files with 16 additions and 12 deletions
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28
db/schema_tables.cc
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@@ -330,31 +330,35 @@ schema_ptr tables() {
// Holds Scylla-specific table metadata.
schema_ptr scylla_tables(schema_features features) {
static auto make = [] (bool has_cdc_options, bool has_per_table_partitioners) -> schema_ptr {
static thread_local schema_ptr schemas[2][2]{};
bool has_cdc_options = features.contains(schema_feature::CDC_OPTIONS);
bool has_per_table_partitioners = features.contains(schema_feature::PER_TABLE_PARTITIONERS);
schema_ptr& s = schemas[has_cdc_options][has_per_table_partitioners];
if (!s) {
auto id = generate_legacy_id(NAME, SCYLLA_TABLES);
auto sb = schema_builder(NAME, SCYLLA_TABLES, std::make_optional(id))
.with_column("keyspace_name", utf8_type, column_kind::partition_key)
.with_column("table_name", utf8_type, column_kind::clustering_key)
.with_column("version", uuid_type)
.set_gc_grace_seconds(schema_gc_grace);
// 0 - false, false
// 1 - true, false
// 2 - false, true
// 3 - true, true
int offset = 0;
// Each bit in `offset` denotes a different schema feature,
// so different values of `offset` are used for different combinations of features.
uint16_t offset = 0;
if (has_cdc_options) {
sb.with_column("cdc", map_type_impl::get_instance(utf8_type, utf8_type, false));
++offset;
offset |= 0b1;
}
if (has_per_table_partitioners) {
sb.with_column("partitioner", utf8_type);
offset += 2;
offset |= 0b10;
}
sb.with_version(system_keyspace::generate_schema_version(id, offset));
return sb.build();
};
static thread_local schema_ptr schemas[2][2] = { {make(false, false), make(false, true)}, {make(true, false), make(true, true)} };
return schemas[features.contains(schema_feature::CDC_OPTIONS)][features.contains(schema_feature::PER_TABLE_PARTITIONERS)];
s = sb.build();
}
return s;
}
// The "columns" table lists the definitions of all columns in all tables