-- CREATE VIEW citus_shard_key_candidates AS
WITH fkeys AS (
        select distinct on (freloid, confkey)
            c.oid as reloid, cf.oid as freloid,
            (select string_agg(attname, ',')
            from pg_attribute a
            where a.attrelid = r.conrelid
                and array[a.attnum::integer] <@ conkey::integer[]
            ) as conkey,
            (select string_agg(attname, ',')
            from pg_attribute a
            where a.attrelid = r.confrelid
                and array[a.attnum::integer] <@ confkey::integer[]
            ) as confkey
    from pg_catalog.pg_constraint r
            JOIN pg_class c on r.conrelid = c.oid
            JOIN pg_namespace n on c.relnamespace = n.oid
            JOIN pg_class cf on r.confrelid = cf.oid
            JOIN pg_namespace nf on cf.relnamespace = nf.oid
            JOIN pg_depend d on d.classid = 'pg_constraint'::regclass
                            and d.objid = r.oid
                            and d.refobjsubid = 0
    where r.contype = 'f'
            AND c.relkind in ('r', 'f', 'p')
            AND cf.relkind in ('r', 'f', 'p')
            AND n.nspname !~ '^pg_' and n.nspname <> 'information_schema'
            AND nf.nspname !~ '^pg_' and nf.nspname <> 'information_schema'
            AND c.relkind = 'r' and c.relpersistence = 'p'
            AND cf.relkind = 'r' and cf.relpersistence = 'p'
)
select n.nspname as schema_name, c.relname as table_name,
       CASE WHEN pkeys.attname IS NULL THEN 'reference' ELSE 'distributed' END AS citus_table_type,
       pkeys.attname as distribution_key,
       CASE
         WHEN pkeys.attname IS NOT NULL
         THEN json_agg(json_object(array['table', 'column'], array[fkeys_d.reloid::regclass::text, fkeys_d.conkey]))
         WHEN COUNT(fkeys_r.reloid) > 0
         THEN json_agg(json_object(array['table', 'column'], array[fkeys_r.freloid::regclass::text, fkeys_r.confkey]))
       END as related_columns
  from pg_catalog.pg_class c
       join pg_catalog.pg_namespace n on c.relnamespace = n.oid
       join pg_roles auth ON auth.oid = c.relowner
       left join lateral (
           select indrelid, indexrelid, a.attname
             from pg_index x
             join pg_class i on i.oid = x.indexrelid
             join pg_attribute a on a.attrelid = c.oid and attnum = indkey[0]
            where x.indrelid = c.oid
              and (indisprimary or indisunique)
              and array_length(indkey::integer[], 1) = 1
              and atttypid in ('smallint'::regtype,
                               'int'::regtype,
                               'bigint'::regtype)
         order by not indisprimary, not indisunique
            limit 1
       ) as pkeys on true
  left join fkeys AS fkeys_d ON (fkeys_d.freloid = c.oid)
  left join fkeys AS fkeys_r ON (fkeys_r.reloid = c.oid)
 where relkind = 'r' and c.relpersistence = 'p'
   and n.nspname !~ '^pg_' and n.nspname <> 'information_schema'
   and not exists
     (
       select 1
         from pg_depend d
        where d.classid = 'pg_class'::regclass
          and d.objid = c.oid
          and d.deptype = 'e'
     )
   and not exists (select 1 from pg_dist_partition where logicalrelid = c.oid)
group by 1,2,3,4
order by citus_table_type, n.nspname, c.relname;