presto-redis/src/main/java/io/prestosql/plugin/redis/RedisMetadata.java/RedisMetadata/listTableColumns
class RedisMetadata:    @Override
    public Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSession session, SchemaTablePrefix prefix)
    {
        requireNonNull(prefix, "prefix is null");

        ImmutableMap.Builder<SchemaTableName, List<ColumnMetadata>> columns = ImmutableMap.builder();

        List<SchemaTableName> tableNames;
        if (!prefix.getTable().isPresent()) {
            tableNames = listTables(session, prefix.getSchema());
        }
        else {
            tableNames = ImmutableList.of(prefix.toSchemaTableName());
        }

        for (SchemaTableName tableName : tableNames) {
            ConnectorTableMetadata tableMetadata = getTableMetadata(tableName);
            // table can disappear during listing operation
            if (tableMetadata != null) {
                columns.put(tableName, tableMetadata.getColumns());
            }
        }
        return columns.build();
    }