As it turns out, each sstable carries its own schema in its serialization header (Statistics component). This schema is incomplete -- the names of the key columns are not stored, just their type. Static and regular columns do have names and types stored however. This bare-bones schema is enough to parse and display the content of the sstable. Another thing missing is schema options (the stuff after the `WITH` keyword, except the clustering order). The only options stored are the compression options (in the CompressionInfo component), this is actually needed to read the Data component.
This series adds a new method to `tools/schema_loader.cc` to extract the schema stored in the sstable itself. This new schema load method is used as the last fall-back for obtaining the schema, in case scylla-sstable is trying to autodetect the schema of the sstable. Although, right now this bare-bones schema is enough for everything scylla-sstable does, it is more future proof to stick to the "full" schema if possible, so this new method is the last resort for now.
Fixes: https://github.com/scylladb/scylladb/issues/17869
Fixes: https://github.com/scylladb/scylladb/issues/18809
New functionality, no backport needed.
Closesscylladb/scylladb#19169
* github.com:scylladb/scylladb:
tools/scylla-sstable: log loaded schema with trace level
tools/scylla-sstable: load schema from the sstable as fallback
tools/schema_loader: introduce load_schema_from_sstable()
test/lib/random_schema: remove assert on min number of regular columns
sstables: introduce load_metadata()
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