I'm working with a quite flat table schema (think: mySQL ;)),
and I want to divide it into two tables.
Lets start with how it looks now:
CREATE TABLE old_table ( id serial PRIMARY KEY, body text, path_a varchar(1024), gendate_a date, path_bb varchar(1024),
gendate_bbdate, path_ccc varchar(1024), gendate_ccc date
);
I want to have:
CREATE TABLE new_table ( id serial PRIMARY KEY, body text
);
CREATE TABLE new_table_paths ( id integer NOT NULL REFERENCES (new_table), pathtype NOT NULL varchar(10), path
varchar(1024),gendate date, PRIMARY KEY(id,pathtype)
);
...what I'm looking for is how to, most efficiently
write a join between new_table and new_table_paths
so it looks like old_table (for compatibility (for other
people)).
I'm thinking about a trigger on schema-table
(with pathtypes), which would automagically update
view whenever schema-table is updated (new pathtype
(like 'a', 'bb', 'ccc')) is added/removed); but this is
implementation.
Now, for the join.
I can write:
SELECT * FROM (SELECT id, path AS path_a FROM new_table_paths WHERE id
= <<NUM>> AND pathtype = 'a') AS a NATURAL FULL OUTER JOIN (SELECT id,
path AS path_bb FROM new_table_paths WHERE id = <<NUM>> AND pathtype =
'bb') AS bb; [ and so on... ]
And its fast; however if I move WHERE id = <<NUM>> outside selects
(for views), it first "materializes" old layout, and then selects
id... total waste.
SELECT * FROM (SELECT id, path AS path_a FROM new_table_paths WHERE
pathtype = 'a') AS a NATURAL FULL OUTER JOIN (SELECT id, path AS
path_bb FROM new_table_paths WHERE pathtype = 'bb') AS bb WHERE id =
<<NUM>>;
I wonder if you know other way to write this join so it has good performace?
Once again, I need a SELECT since I want a VIEW. :-)
Regards, Dawid
