Re: Effective query for listing flags in use by messages in a folder

drop table if EXISTS message;
create table message(    folder_id integer not NULL,    msg varchar NOT NULL,    is_seen boolean NOT NULL default false,    is_replied boolean not null default false,    is_forwarded boolean not null default false,    is_deleted boolean not null default false,    is_draft boolean not null default false,    is_flagged boolean not null default false
);

INSERT INTO message(folder_id, msg, is_seen, is_replied, is_forwarded, is_deleted, is_draft, is_flagged)
values(1, 'msg a', FALSE, FALSE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg b', TRUE, FALSE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg c', TRUE, FALSE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg d', TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg e', TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg f', FALSE, FALSE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg g', FALSE, FALSE, FALSE, FALSE, FALSE, FALSE)    , (1, 'msg h', TRUE, FALSE, FALSE, TRUE, FALSE, FALSE)
;

create index message_folder_id_deleted_idx ON message(folder_id) where is_deleted = TRUE;
create index message_folder_id_forwarded_idx ON message(folder_id) where is_forwarded = TRUE;
create index message_folder_id_replied_idx ON message(folder_id) where is_replied = TRUE;
create index message_folder_id_seen_idx ON message(folder_id) where is_seen = TRUE;
create index message_folder_id_flagged_idx ON message(folder_id) where is_flagged = TRUE;
create index message_folder_id_draft_idx ON message(folder_id) where is_draft = TRUE;

select 'is_deleted' as falgs from (select * from message where folder_id = 1 AND is_deleted limit 1) as q
UNION
select 'is_forwarded' from (select * from message where folder_id = 1 AND is_forwarded limit 1) as q
UNION
select 'is_replied' from (select * from message where folder_id = 1 AND is_replied limit 1) as q
UNION
select 'is_seen' from (select * from message where folder_id = 1 AND is_seen limit 1) as q
UNION
select 'is_flagged' from (select * from message where folder_id = 1 AND is_flagged limit 1) as q
UNION
select 'is_draft' from (select * from message where folder_id = 1 AND is_draft limit 1) as q
;