Clear PostgreSQL database for all content

Question

I want to remove all content from a database without dropping and re-creating the database.

I figured out that dropping all schemas, re-creating 'public' and dropping all temporary tables is a good start. Am I getting rid of all content compared to a "virgin" database or missing something?

const systemSchemas = ['pg_toast', 'pg_temp_1', 'pg_toast_temp_1', 'pg_catalog', 'information_schema']

return Database.connect(connectionString, db => {

  // DROP schemas except systemSchemas
  const schemas = await db.queryRows(`SELECT nspname AS name FROM pg_catalog.pg_namespace ORDER BY nspname`).map(row => row.name).filter(name => {
    return systemSchemas.includes(name) === false
  })
  await Promise.resolve(schemas).each(name => db.query(`DROP SCHEMA "${name}" CASCADE`))

  // DROP temporary tables
  const sql = `SELECT c.relname AS name FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE n.nspname like 'pg_temp_%' AND pg_catalog.pg_table_is_visible(c.oid) AND c.relpersistence = 't'`
  return db.queryRows(sql).each(row => db.query(`DROP TABLE IF EXISTS "${row.name}"`))

  // CREATE public schema
  return db.query(`CREATE SCHEMA public`)
  .then(() => db.query(`GRANT ALL ON SCHEMA public TO postgres`))
  .then(() => db.query(`GRANT ALL ON SCHEMA public TO public`))
})

klin · Accepted Answer · 2017-03-09 12:59:10Z

4

You cannot exclude just pg_temp_1 and pg_toast_temp_1 because there may be more temporary schemas. It seems that it is sufficient to drop all non-system schemas including temporary ones, so you should exclude only pg_catalog, information_schema and pg_toast and not try to drop temporary tables.

Note that you can do this in a single DO Postgres command:

do $$
declare
    schema_name text;
begin
    for schema_name in
        select nspname
        from pg_catalog.pg_namespace 
        where nspname not in ('pg_catalog', 'information_schema', 'pg_toast')
    loop
        execute format('drop schema %s cascade', schema_name);
    end loop;
    create schema public;
    grant all on schema public to postgres;
    grant all on schema public to public;
    comment on schema public is 'standard public schema';
end;
$$;

answered Mar 9, 2017 at 12:59

klin

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1 Comment

Jacob Over a year ago

Great! Thank you.

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