使数据库中的所有表 UNLOGGED

Question

I want to decrease local test execution time by making all tables UNLOGGED . I want to write sql script, which will run after all conversion and make them UNLOGGED . But I found problem - tables relate each other with FK , so postgresql prohibit make table UNLOGGED (through ALTER ) if it related from other table which is not UNLOGGED yet.

Is there better way then list all ALTER in correct order - I have more then 150 tables? For example, apply it on database level.

Answer 1

You have to ALTER them in right order I'm afraid. You can select https://www.postgresql.org/docs/current/static/catalog-pg-constraint.html and loop for referencing tables first and then alter the rest:

begin;
do
$$
declare
 _r record;
 _t text;
begin
 for _r in (
    select relname,conrelid
    from pg_constraint
    join pg_class c on c.oid = conrelid
    where confkey is not null
    order by conrelid desc
    -- Order by oid with logic that you should start from latest added objects to earliest - of course it does not garantee anything
 ) loop
    _t := format('alter table %I set unlogged',_r.relname);
    raise info '%',_t;
    execute _t;
 end loop;

  for _r in (select tablename from pg_tables where tablename like 's%' and schemaname = 'public') loop
    _t := format('alter table %I set unlogged',_r.tablename);
    raise info '%',_t;
    execute _t;
 end loop;

end;
$$
;
rollback;

By all means it will fail if you have recursive FK:

t=# create table s134(i int primary key, e int);
CREATE TABLE
t=# create table s135(i int references s134(i), e int primary key);
CREATE TABLE
t=# alter table s134 add constraint c1 foreign key (e) references s135(e);
ALTER TABLE
t=# alter table s134 set unlogged;
ERROR:  could not change table "s134" to unlogged because it references logged table "s135"
t=# alter table s135 set unlogged;
ERROR:  could not change table "s135" to unlogged because it references logged table "s134"

But you would not achieve that any way I believe.

Also don't forget that after unclean shutdown or failure unlogged tables will be truncated.

And lastly you say "after all conversion" - if you create, convert etc, maybe you should just create them unlogged?..

Answer 2

I would drop and re-create all foreign keys. You can automate this.

The following query will generate the necessary DDL statements for all foreign keys. You need to save the output of that into a file, which you can later use to restore all foreign keys.

select format('alter table %I.%I add constraint %I ',  ns.nspname, tb.relname, conname)|| 
       pg_get_constraintdef(c.oid, true)||';' as ddl
from pg_constraint c
  join pg_class tb on tb.oid = c.conrelid
  join pg_namespace ns on ns.oid = tb.relnamespace
where ns.nspname not in ('pg_catalog', 'information_schema')
  and ns.nspname not like 'pg_temp%'
  and c.contype in ('f')

Then generate a script to drop all constraints:

select format('alter table %I.%I drop constraint %I cascade;', ns.nspname, tb.relname, c.conname) as ddl
from pg_constraint c
  join pg_class tb on tb.oid = c.conrelid
  join pg_namespace ns on ns.oid = tb.relnamespace
where ns.nspname not in ('pg_catalog', 'information_schema')
  and ns.nspname not like 'pg_temp%'
  and c.contype in ('f');

Of course you have to run the query to generate the FKs before you drop them ;)

Answer 3

I had difficulties with the accepted answer, because it relies on a heuristic (which may not apply) to get the ordering correct. I have reworked the suggested answer using a (somewhat verbose) recursive query which allows one to get an exact ordering required. I have not tested it with recursive FKs, I suspect that the recursive query will not terminate. Note that I have restricted the query to apply to tables in the public schema, modify to suit your own needs.

Unlog all tables:

do
$$
    declare
        _r record;
        _t text;
    begin
        for _r in (
            WITH RECURSIVE constraints AS (
                SELECT
                    tc.table_schema
                     , tc.table_name
                     , kcu.column_name
                     , ccu.table_name AS foreign_table_name
                FROM
                    information_schema.table_constraints AS tc
                        LEFT OUTER JOIN information_schema.key_column_usage AS kcu
                                        ON tc.constraint_name = kcu.constraint_name
                                            AND tc.table_schema = kcu.table_schema
                        LEFT OUTER JOIN information_schema.constraint_column_usage AS ccu
                                        ON ccu.constraint_name = tc.constraint_name
                                            AND ccu.table_schema = tc.table_schema
                WHERE (tc.constraint_type IS NULL OR tc.constraint_type = 'FOREIGN KEY'))
               , tables_and_constraints AS (
                SELECT
                    t.table_schema
                     , t.table_name
                     , c.foreign_table_name
                FROM information_schema.tables AS t
                         LEFT JOIN constraints AS c USING (table_name)
                WHERE t.table_type <> 'VIEW')
               , dependent_table_constraints AS (
                SELECT tc.table_schema
                     , tc.table_name
                     , tc.foreign_table_name
                     , 0 AS depth
                FROM tables_and_constraints AS tc
                WHERE foreign_table_name IS NULL
                UNION
                SELECT tc.table_schema
                     , tc.table_name
                     , tc.foreign_table_name
                     , dtc.depth + 1
                FROM tables_and_constraints AS tc
                         INNER JOIN dependent_table_constraints AS dtc ON tc.foreign_table_name = dtc.table_name
            ) SELECT table_name, max(depth) as depth FROM dependent_table_constraints
            WHERE table_schema = 'public'
            GROUP BY table_name
            ORDER BY depth DESC
        ) loop
                _t := format('ALTER TABLE %I SET UNLOGGED',_r.table_name);
                raise info '%',_t;
                execute _t;
            end loop;
    end;
$$
;

Relog all tables:

do
$$
    declare
        _r record;
        _t text;
    begin
        for _r in (
            WITH RECURSIVE constraints AS (
                SELECT
                    tc.table_schema
                     , tc.table_name
                     , kcu.column_name
                     , ccu.table_name AS foreign_table_name
                FROM
                    information_schema.table_constraints AS tc
                        LEFT OUTER JOIN information_schema.key_column_usage AS kcu
                                        ON tc.constraint_name = kcu.constraint_name
                                            AND tc.table_schema = kcu.table_schema
                        LEFT OUTER JOIN information_schema.constraint_column_usage AS ccu
                                        ON ccu.constraint_name = tc.constraint_name
                                            AND ccu.table_schema = tc.table_schema
                WHERE (tc.constraint_type IS NULL OR tc.constraint_type = 'FOREIGN KEY'))
               , tables_and_constraints AS (
                SELECT
                    t.table_schema
                     , t.table_name
                     , c.foreign_table_name
                FROM information_schema.tables AS t
                         LEFT JOIN constraints AS c USING (table_name)
                WHERE t.table_type <> 'VIEW')
               , dependent_table_constraints AS (
                SELECT tc.table_schema
                     , tc.table_name
                     , tc.foreign_table_name
                     , 0 AS depth
                FROM tables_and_constraints AS tc
                WHERE foreign_table_name IS NULL
                UNION
                SELECT tc.table_schema
                     , tc.table_name
                     , tc.foreign_table_name
                     , dtc.depth + 1
                FROM tables_and_constraints AS tc
                         INNER JOIN dependent_table_constraints AS dtc ON tc.foreign_table_name = dtc.table_name
            ) SELECT table_name, max(depth) as depth FROM dependent_table_constraints
            WHERE table_schema = 'public'
            GROUP BY table_name
            ORDER BY depth ASC
        ) loop
                _t := format('ALTER TABLE %I SET LOGGED',_r.table_name);
                raise info '%',_t;
                execute _t;
            end loop;
    end;
$$
;