-- A write buffer larger than maintenance_work_mem is promoted through a sort that spills to disk, in key order, and
-- the immutable segment answers like the write buffer did.
CREATE EXTENSION pg_sift;
SET sift.async_maintenance = off;
SET maintenance_work_mem = '1MB';
SET enable_seqscan = off;
CREATE TABLE ps (id serial, body text) WITH (autovacuum_enabled = off);
CREATE INDEX ps_idx ON ps USING sift (body) WITH (write_buffer_limit = 1048576);
INSERT INTO ps (body)
SELECT string_agg('t' || ((g * 7 + j * 13) % 2003) || ' u' || (g % 31) || ' common', ' ') FROM generate_series(1, 6000) g, generate_series(1, 40) j GROUP BY g ORDER BY g;
DELETE FROM ps WHERE id % 10 = 0;
SELECT kind, ndocs FROM sift.segments('ps_idx') ORDER BY gen;
  kind  | ndocs 
--------+-------
 buffer |  6000
(1 row)

SELECT count(*) FROM ps WHERE body @@> 'common';
 count 
-------
  5400
(1 row)

SELECT count(*) FROM ps WHERE body @@> 't5 AND u3';
 count 
-------
     3
(1 row)

SELECT count(*) FROM ps WHERE body @@> 't1000 OR t1999';
 count 
-------
   216
(1 row)

SELECT sift.promote('ps_idx');
 promote 
---------
       1
(1 row)

SELECT kind, ndocs FROM sift.segments('ps_idx') ORDER BY gen;
   kind    | ndocs 
-----------+-------
 buffer    |     0
 immutable |  6000
(2 rows)

SELECT count(*) FROM ps WHERE body @@> 'common';
 count 
-------
  5400
(1 row)

SELECT count(*) FROM ps WHERE body @@> 't5 AND u3';
 count 
-------
     3
(1 row)

SELECT count(*) FROM ps WHERE body @@> 't1000 OR t1999';
 count 
-------
   216
(1 row)

SELECT sift.verify('ps_idx', true);
 verify 
--------
 
(1 row)

DROP TABLE ps;
DROP EXTENSION pg_sift;