I've got the following table:
CREATE TABLE gorfs.inode_segments ( st_ino "gorfs"."ino_t" NOT NULL, -- Inode number the segment belongs to. alongside segment_index, it forms the table's primary key to ensure uniqueness per relevant scope segment_index "gorfs"."pathname_component" NOT NULL, -- See st_no's column description for further details. The meaning of this column varies based on the host inode type:... st_ino_target "gorfs"."ino_t", -- Target inode number. Meaningful for directory inode segments (objects in the directory) full_path "gorfs"."absolute_pathname", -- Exploded absolute canonical path for quick lookups. Meaningful only for directory inode segments (objects in the directory) segment_data "bytea", -- Actual data segment. Meaningful only for S_IFLNK and S_IFREG.... CONSTRAINT pk_inode_segments PRIMARY KEY ("st_ino", "segment_index"), CONSTRAINT fk_host_inode_must_exist FOREIGN KEY (st_ino) REFERENCES gorfs.inodes (st_ino) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION, CONSTRAINT fk_target_inode_must_exist FOREIGN KEY (st_ino_target) REFERENCES gorfs.inodes (st_ino) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION, CONSTRAINT uc_no_duplicate_full_paths UNIQUE ("full_path"), CONSTRAINT cc_only_root_can_be_its_own_parent CHECK ("st_ino_target" IS NULL OR "st_ino"::bigint <> "st_ino_target"::bigint OR "st_ino"::bigint = 2) )
The column "segment_data" has all the attachments from the customers, like photos, documents, audio, etc.
To improve the performance, we'll be migrating all the data from the segment_data column to a NFS server.
Full database size: 2 TB
Using PostgreSQL 9.2
Table gorfs.inode_segments size: 1698 GB (Command: SELECT pg_size_pretty( pg_total_relation_size('gorfs.inode_segments'));)
Basically we'll be using: UPDATE gorfs.inode_segments SET segment_data = NULL WHERE batch_number = 0
We won't be migrating all the data on the segment_data column by once, it will be done gradually (over few weeks).
Just by setting "NULL" into that column, will I get free space on the database? Will I have to run any command such VACUUM/VACUUM FULL/ANALYZE/PG_DUMP?