pg\_surgery {#pgsurgery}
===========

pg\_surgery

The `pg_surgery` module provides various functions to perform surgery on
a damaged relation. These functions are unsafe by design and using them
may corrupt (or further corrupt) your database. For example, these
functions can easily be used to make a table inconsistent with its own
indexes, to cause `UNIQUE` or `FOREIGN KEY` constraint violations, or
even to make tuples visible which, when read, will cause a database
server crash. They should be used with great caution and only as a last
resort.

Functions
---------

`heap_force_kill(regclass, tid[]) returns void`

:   `heap_force_kill` marks "used" line pointers as "dead" without
    examining the tuples. The intended use of this function is to
    forcibly remove tuples that are not otherwise accessible. For
    example:

        test=> select * from t1 where ctid = '(0, 1)';
        ERROR:  could not access status of transaction 4007513275
        DETAIL:  Could not open file "pg_xact/0EED": No such file or directory.

        test=# select heap_force_kill('t1'::regclass, ARRAY['(0, 1)']::tid[]);
         heap_force_kill 
        -----------------
         
        (1 row)

        test=# select * from t1 where ctid = '(0, 1)';
        (0 rows)

`heap_force_freeze(regclass, tid[]) returns void`

:   `heap_force_freeze` marks tuples as frozen without examining the
    tuple data. The intended use of this function is to make accessible
    tuples which are inaccessible due to corrupted visibility
    information, or which prevent the table from being successfully
    vacuumed due to corrupted visibility information. For example:

        test=> vacuum t1;
        ERROR:  found xmin 507 from before relfrozenxid 515
        CONTEXT:  while scanning block 0 of relation "public.t1"

        test=# select ctid from t1 where xmin = 507;
         ctid  
        -------
         (0,3)
        (1 row)

        test=# select heap_force_freeze('t1'::regclass, ARRAY['(0, 3)']::tid[]);
         heap_force_freeze 
        -------------------
         
        (1 row)

        test=# select ctid from t1 where xmin = 2;
         ctid
        -------
         (0,3)
        (1 row)

Authors
-------

Ashutosh Sharma <ashu.coek88@gmail.com>
