SELECT count(*) AS columnar_table_count FROM cstore.cstore_data_files \gset CREATE TABLE t(a int, b int) USING cstore_tableam; SELECT count(*) FROM cstore.cstore_stripes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t'; count ------- 0 (1 row) INSERT INTO t SELECT i, i * i FROM generate_series(1, 10) i; INSERT INTO t SELECT i, i * i FROM generate_series(11, 20) i; INSERT INTO t SELECT i, i * i FROM generate_series(21, 30) i; SELECT sum(a), sum(b) FROM t; sum | sum -----+------ 465 | 9455 (1 row) SELECT count(*) FROM cstore.cstore_stripes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t'; count ------- 3 (1 row) -- vacuum full should merge stripes together VACUUM FULL t; SELECT sum(a), sum(b) FROM t; sum | sum -----+------ 465 | 9455 (1 row) SELECT count(*) FROM cstore.cstore_stripes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t'; count ------- 1 (1 row) -- test the case when all data cannot fit into a single stripe SET cstore.stripe_row_count TO 1000; INSERT INTO t SELECT i, 2 * i FROM generate_series(1,2500) i; SELECT sum(a), sum(b) FROM t; sum | sum ---------+--------- 3126715 | 6261955 (1 row) SELECT count(*) FROM cstore.cstore_stripes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t'; count ------- 4 (1 row) VACUUM FULL t; SELECT sum(a), sum(b) FROM t; sum | sum ---------+--------- 3126715 | 6261955 (1 row) SELECT count(*) FROM cstore.cstore_stripes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t'; count ------- 3 (1 row) -- VACUUM FULL doesn't reclaim dropped columns, but converts them to NULLs ALTER TABLE t DROP COLUMN a; SELECT stripe, attr, block, minimum_value IS NULL, maximum_value IS NULL FROM cstore.cstore_skipnodes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t' ORDER BY 1, 2, 3; stripe | attr | block | ?column? | ?column? --------+------+-------+----------+---------- 1 | 1 | 0 | f | f 1 | 2 | 0 | f | f 2 | 1 | 0 | f | f 2 | 2 | 0 | f | f 3 | 1 | 0 | f | f 3 | 2 | 0 | f | f (6 rows) VACUUM FULL t; SELECT stripe, attr, block, minimum_value IS NULL, maximum_value IS NULL FROM cstore.cstore_skipnodes a, pg_class b WHERE a.relfilenode=b.relfilenode AND b.relname='t' ORDER BY 1, 2, 3; stripe | attr | block | ?column? | ?column? --------+------+-------+----------+---------- 1 | 1 | 0 | t | t 1 | 2 | 0 | f | f 2 | 1 | 0 | t | t 2 | 2 | 0 | f | f 3 | 1 | 0 | t | t 3 | 2 | 0 | f | f (6 rows) -- Make sure we cleaned-up the transient table metadata after VACUUM FULL commands SELECT count(*) - :columnar_table_count FROM cstore.cstore_data_files; ?column? ---------- 1 (1 row) -- do this in a transaction so concurrent autovacuum doesn't interfere with results BEGIN; SAVEPOINT s1; SELECT count(*) FROM t; count ------- 2530 (1 row) SELECT pg_size_pretty(pg_relation_size('t')); pg_size_pretty ---------------- 32 kB (1 row) INSERT INTO t SELECT i FROM generate_series(1, 10000) i; SELECT pg_size_pretty(pg_relation_size('t')); pg_size_pretty ---------------- 112 kB (1 row) SELECT count(*) FROM t; count ------- 12530 (1 row) ROLLBACK TO SAVEPOINT s1; -- not truncated by VACUUM or autovacuum yet (being in transaction ensures this), -- so relation size should be same as before. SELECT pg_size_pretty(pg_relation_size('t')); pg_size_pretty ---------------- 112 kB (1 row) COMMIT; -- vacuum should truncate the relation to the usable space VACUUM VERBOSE t; INFO: statistics for "t": total file size: 114688, total data size: 10754 total row count: 2530, stripe count: 3, average rows per stripe: 843 block count: 3, containing data for dropped columns: 0, none compressed: 3, pglz compressed: 0 INFO: "t": truncated 14 to 4 pages DETAIL: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s SELECT pg_size_pretty(pg_relation_size('t')); pg_size_pretty ---------------- 32 kB (1 row) SELECT count(*) FROM t; count ------- 2530 (1 row) -- add some stripes with different compression types and create some gaps, -- then vacuum to print stats BEGIN; SET cstore.block_row_count TO 1000; SET cstore.stripe_row_count TO 2000; SET cstore.compression TO "pglz"; SAVEPOINT s1; INSERT INTO t SELECT i FROM generate_series(1, 1500) i; ROLLBACK TO SAVEPOINT s1; INSERT INTO t SELECT i / 5 FROM generate_series(1, 1500) i; SET cstore.compression TO "none"; SAVEPOINT s2; INSERT INTO t SELECT i FROM generate_series(1, 1500) i; ROLLBACK TO SAVEPOINT s2; INSERT INTO t SELECT i / 5 FROM generate_series(1, 1500) i; COMMIT; VACUUM VERBOSE t; INFO: statistics for "t": total file size: 49152, total data size: 18808 total row count: 5530, stripe count: 5, average rows per stripe: 1106 block count: 7, containing data for dropped columns: 0, none compressed: 5, pglz compressed: 2 SELECT count(*) FROM t; count ------- 5530 (1 row) -- check that we report blocks with data for dropped columns ALTER TABLE t ADD COLUMN c int; INSERT INTO t SELECT 1, i / 5 FROM generate_series(1, 1500) i; ALTER TABLE t DROP COLUMN c; VACUUM VERBOSE t; INFO: statistics for "t": total file size: 65536, total data size: 31372 total row count: 7030, stripe count: 6, average rows per stripe: 1171 block count: 11, containing data for dropped columns: 2, none compressed: 9, pglz compressed: 2 -- vacuum full should remove blocks for dropped columns -- note that, a block will be stored in non-compressed for if compression -- doesn't reduce its size. SET cstore.compression TO "pglz"; VACUUM FULL t; VACUUM VERBOSE t; INFO: statistics for "t": total file size: 49152, total data size: 15728 total row count: 7030, stripe count: 4, average rows per stripe: 1757 block count: 8, containing data for dropped columns: 0, none compressed: 2, pglz compressed: 6 DROP TABLE t; -- Make sure we cleaned the metadata for t too SELECT count(*) - :columnar_table_count FROM cstore.cstore_data_files; ?column? ---------- 0 (1 row)