| Hi, I’m facing of a comportement I don’t understand on indexes, here a quick example to reproduce my problem test=# select version(); version ---------------------------------------------------------------------------------------------------------------------------------- PostgreSQL 12.4 (Debian 12.4-1.pgdg90+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit (1 row) test=# create table plop (col_a int, col_b int, col_c int); CREATE TABLE test=# create unique index on plop (col_a); CREATE INDEX test=# create index on plop(col_b); CREATE INDEX test=# insert into plop (col_a, col_b) select generate_series(1, 10000), generate_series(1, 10000); INSERT 0 10000 test=# SELECT schemaname, tablename, pg_size_pretty(SIZE) AS size_pretty, pg_size_pretty(total_size) AS total_size_pretty FROM (SELECT *, pg_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS SIZE, pg_total_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS total_size FROM pg_tables) AS TABLES where tablename = 'plop'; schemaname | tablename | size_pretty | total_size_pretty ------------+-----------+-------------+------------------- public | plop | 360 kB | 864 kB (1 row) test=# update plop set col_c = floor(random() * 10 + 1)::int; UPDATE 10000 test=# SELECT schemaname, tablename, pg_size_pretty(SIZE) AS size_pretty, pg_size_pretty(total_size) AS total_size_pretty FROM (SELECT *, pg_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS SIZE, pg_total_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS total_size FROM pg_tables) AS TABLES where tablename = 'plop'; schemaname | tablename | size_pretty | total_size_pretty ------------+-----------+-------------+------------------- public | plop | 792 kB | 2160 kB (1 row) test=# reindex table plop; REINDEX test=# SELECT schemaname, tablename, pg_size_pretty(SIZE) AS size_pretty, pg_size_pretty(total_size) AS total_size_pretty FROM (SELECT *, pg_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS SIZE, pg_total_relation_size(quote_ident(schemaname) || '.' || quote_ident(tablename)) AS total_size FROM pg_tables) AS TABLES where tablename = 'plop'; schemaname | tablename | size_pretty | total_size_pretty ------------+-----------+-------------+------------------- public | plop | 792 kB | 1304 kB (1 row) I don’t understand why after the update where I only update a non indexed column the indexes size is growing. Is it something someone can explain ? Regards, Guillaume |
