after creating a table wiki_data_part with partition by list (category);
and creating partitions like CREATE TABLE wiki_data_part_a PARTITION OF wiki_data_part FOR VALUES IN ('ang.q',...,'arc'); CREATE TABLE wiki_data_part_b PARTITION OF wiki_data_part FOR VALUES IN ('bs.s',...,'bg.n');
copy table wiki_data_part from ...;
analyze wiki_data_part;
explain select * from wiki_data_part where category='en'