F.34. pg_surgery — perform low-level surgery on relation data

F.34. pg_surgery — perform low-level surgery on relation data
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F.34. pg_surgery — perform low-level surgery on relation data #

F.34.1. Functions
F.34.2. Authors

+ 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. +

F.34.1. 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)
+
+

F.34.2. Authors #

+ Ashutosh Sharma <ashu.coek88@gmail.com> +

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