I found that GridDB FDW does not operate correctly. Could you please help me to fix it? I have a scenario as below which
set local min_parallel_table_scan_size = 0;
set local parallel_setup_cost = 0;
-- Extract bucket and batch counts from an explain analyze plan. In
-- general we can't make assertions about how many batches (or
-- buckets) will be required because it can vary, but we can in some
-- special cases and we can check for growth.
create or replace function find_hash(node json)
returns json language plpgsql
as
$$
declare
x json;
child json;
begin
if node->>'Node Type' = 'Hash' then
return node;
else
for child in select json_array_elements(node->'Plans')
loop
x := find_hash(child);
if x is not null then
return x;
end if;
end loop;
return null;
end if;
end;
$$;
create or replace function hash_join_batches(query text)
returns table (original int, final int) language plpgsql
as
$$
declare
whole_plan json;
hash_node json;
begin
for whole_plan in
execute 'explain (analyze, format ''json'') ' || query
loop
hash_node := find_hash(json_extract_path(whole_plan, '0', 'Plan'));
original := hash_node->>'Original Hash Batches';
final := hash_node->>'Hash Batches';
return next;
end loop;
end;
$$;`
The hash_join_batches function does not operate correctly because the merge join algorithm is selected by the query select count(*) from simple r join simple s using (id); instead of the hash join algorithm.
After I tried SET ENABLE_MERGEJOIN TO off, hash join algorithm is selected, but issue still exist.
