Hi, I think you need to read this: https://www.postgresql.org/docs/current/static/storage-file-layout.html On 11/27/2017 04:19 PM, Martin Mueller wrote: > Apologies if I asked this question before. > > I’m a newcomer to Postgres, having migrated from Mysql. Information > about tables seems harder to get at in Postgres. That data directory > on my machine is suspiciously large—well over 100 GB. The directory > Postgres/var-9.5/base/ contains a number of subdirectories with > Arabic numerals. Each of those directories stores data for a single database. Each object (including databases) has a 32-bit identifier, mapping it to object on the filesystem. databases: SELECT oid, datname FROM pg_database; tables etc.: SELECT relfilenode, relname FROM pg_class; > Directory 16385 has a subdirectory 17463 with a size of 1.07 GB. That's not a subdirectory, but a datafile segment. > But there are also 17 subdirectories with names from 17463.1 to > 17.463.17. There are also other entries with similar forms of > duplication and suspiciously identical file sizes of 1.07GB. > Again, those are files, not subdirectories. Large datafiles are split into 1GB segments, so for example 10GB table with relfilenode 17463 will be stored in files 17463, 17463.1, 17463.2, ..., 17463.9 > Is this normal behavior? Where in the postgres documentation do I > read up on this? Postgres strikes me as superior to MySQl, especially > with regard to string functions and regular expressions, but it’s > harder to look under the hood. https://www.postgresql.org/docs/current/static/storage-file-layout.html > How, for instance, do I figure out what number corresponds to the > table that I know as ‘earlyprinttuples > SELECT relfilenode FROM pg_class WHERE relname = 'earlyprinttuples'; regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
