Dominique Devienne schrieb am 10.01.2025 um 10:41: > On Fri, Jan 10, 2025 at 10:13 AM Vladlen Popolitov > <v.popoli...@postgrespro.ru> wrote: >> If you really need 1-byte integer, you can use "char" type. Cast it >> to/from int. See comment at the end of the page >> https://www.postgresql.org/docs/17/datatype-character.html > > Hi. What would be the best online doc to learn about the physical > storage / format for rows/pages/btree, etc... To understand alignment, > packing, varint or not, all those things. I'm quite familiar with the > [SQLite format][1], having read that doc dozens of times, and I'd like > a better low-level understanding for PostgreSQL as well. TIA, --DD
The alignment requirement of each type is available in pg_type https://www.postgresql.org/docs/current/catalog-pg-type.html The physical layout on disk is described here: https://www.postgresql.org/docs/current/storage.html And the "Postgres intenrals" site might be helpful as well: https://www.interdb.jp/pg/pgsql01.html There are various (blog) posts on how to optimize space considering alignment * https://stackoverflow.com/a/7431468 * https://www.enterprisedb.com/blog/rocks-and-sand The "postgres_dba" toolset has a little SQL script to evaluate the space savings: https://github.com/NikolayS/postgres_dba/blob/master/sql/p1_alignment_padding.sql
