Our db clearing takes like 5ms (large schema from mature company, not a toy). We start by restoring a production schema dump which ensures our test db / devdb schema is basically identical to what we run in production. Any migrations you are working on in your branch get added to the restore of the prod schema after it runs. Building a schema from ORM definitions is what you do if you don't care about your life or time. Clearing the test db takes something similar. This is fine, using template db's is a good way to make a scratch copy of a local database to test migrations (rsync is better if you are technical enough to use it to restore after destructive changes).
Timings:
- create testdb: 9ms
- restore prod schema: 500ms (done once per test process)
- clear test data in 96 tables between tests that write to db (5ms)
The fastest way to clear a test db is to run a query to get every schema/table name, then run ";".join("`DELETE FROM {schema}.{tablename};" for schema, table in my_tables) after putting the db in replica mode. This takes single digit ms a lot of the time even with a decent amount of test data. I've done it every which way and this is by far the fastest way to clear data between tests.
-- This will work on basically any postgresql database with basically any schema so just use it.
test_db_2235191=# CREATE OR REPLACE PROCEDURE public.delete_all_table_data()
LANGUAGE plpgsql
AS $procedure$
DECLARE
target record;
previous_replication_role text;
BEGIN
previous_replication_role :=
current_setting('session_replication_role');
PERFORM set_config('session_replication_role', 'replica', true);
BEGIN
FOR target IN
SELECT namespace.nspname AS schema_name,
relation.relname AS table_name
FROM pg_catalog.pg_class AS relation
JOIN pg_catalog.pg_namespace AS namespace
ON namespace.oid = relation.relnamespace
WHERE relation.relkind = 'r'
AND namespace.nspname NOT LIKE 'pg\_%' ESCAPE '\'
AND namespace.nspname <> 'information_schema'
ORDER BY namespace.nspname, relation.relname
LOOP
RAISE NOTICE 'Deleting %.%',
target.schema_name,
target.table_name;
EXECUTE format(
'DELETE FROM %I.%I',
target.schema_name,
target.table_name
);
END LOOP;
EXCEPTION
WHEN OTHERS THEN
PERFORM set_config(
'session_replication_role',
previous_replication_role,
true
);
RAISE;
END;
PERFORM set_config(
'session_replication_role',
previous_replication_role,
true
);
END;
$procedure$;
CREATE PROCEDURE
Time: 0.840 ms
test_db_2235191=# CALL public.delete_all_table_data();
NOTICE: ... (notices removed for 96 tables)
CALL
Time: 5.855 ms
Timings:
The fastest way to clear a test db is to run a query to get every schema/table name, then run ";".join("`DELETE FROM {schema}.{tablename};" for schema, table in my_tables) after putting the db in replica mode. This takes single digit ms a lot of the time even with a decent amount of test data. I've done it every which way and this is by far the fastest way to clear data between tests.https://www.postgresql.org/docs/current/wal-async-commit.htm...