presto-memory/src/main/java/io/prestosql/plugin/memory/MemoryMetadata.java/MemoryMetadata/listTableColumns
class MemoryMetadata:    @Override
    public synchronized Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSession session, SchemaTablePrefix prefix)
    {
        return tables.values().stream()
                .filter(table -> prefix.matches(table.getSchemaTableName()))
                .collect(toMap(TableInfo::getSchemaTableName, handle -> handle.getMetadata().getColumns()));
    }