reindex

REINDEX()			 SQL Commands			    REINDEX()



NAME
       REINDEX - rebuild indexes


SYNOPSIS
       REINDEX { DATABASE | TABLE | INDEX } name [ FORCE ]


DESCRIPTION
       REINDEX	rebuilds  an  index  based  on	the data stored in the table,
       replacing the old copy of the index. There are two main reasons to use
       REINDEX:

       · An  index  has	 become corrupted, and no longer contains valid data.
	 Although in theory this should never happen, in practice indexes may
	 become	 corrupted due to software bugs or hardware failures. REINDEX
	 provides a recovery method.

       · The index in question contains a lot of dead index  pages  that  are
	 not  being  reclaimed.	 This  can occur with B-tree indexes in Post-
	 greSQL under certain access patterns.	REINDEX	 provides  a  way  to
	 reduce	 the  space consumption of the index by writing a new version
	 of the index without the dead pages. See [XRef	 to  ROUTINE-REINDEX]
	 for more information.


PARAMETERS
       DATABASE
	      Recreate all system indexes of a specified database. Indexes on
	      user tables are not processed. Also, indexes on  shared  system
	      catalogs are skipped except in stand-alone mode (see below).

       TABLE  Recreate	all  indexes of a specified table. If the table has a
	      secondary ‘‘TOAST’’ table, that is reindexed as well.

       INDEX  Recreate a specified index.

       name   The name of the specific database, table, or index to be	rein-
	      dexed. Table and index names may be schema-qualified.

       FORCE  This is an obsolete option; it is ignored if specified.

NOTES
       If  you suspect corruption of an index on a user table, you can simply
       rebuild that index, or all indexes on the table, using  REINDEX	INDEX
       or  REINDEX  TABLE. Another approach to dealing with a corrupted user-
       table index is just to drop and recreate	 it.  This  may	 in  fact  be
       preferable  if  you  would  like	 to maintain some semblance of normal
       operation on the table meanwhile. REINDEX acquires exclusive  lock  on
       the  table,  while CREATE INDEX only locks out writes not reads of the
       table.

       Things are more difficult if you need to recover from corruption of an
       index on a system table. In this case it’s important for the system to
       not have used any of the suspect indexes	 itself.   (Indeed,  in	 this
       sort of scenario you may find that server processes are crashing imme-
       diately at start-up, due to reliance on	the  corrupted	indexes.)  To
       recover	safely,	 the server must be started with the -P option, which
       prevents it from using indexes for system catalog lookups.

       One way to do this is to shut down the postmaster and start  a  stand-
       alone  PostgreSQL  server  with	the -P option included on its command
       line.  Then, REINDEX DATABASE, REINDEX TABLE, or REINDEX INDEX can  be
       issued,	depending  on  how much you want to reconstruct. If in doubt,
       use REINDEX DATABASE to select reconstruction of all system indexes in
       the  database. Then quit the standalone server session and restart the
       regular server.	See the postgres(1) reference page for more  informa-
       tion about how to interact with the stand-alone server interface.

       Alternatively,  a  regular  server  session  can	 be  started  with -P
       included in its command line  options.	The  method  for  doing	 this
       varies  across clients, but in all libpq-based clients, it is possible
       to set the PGOPTIONS environment variable to -P	before	starting  the
       client. Note that while this method does not require locking out other
       clients, it may still be wise to prevent other users  from  connecting
       to the damaged database until repairs have been completed.

       If  corruption is suspected in the indexes of any of the shared system
       catalogs (pg_database, pg_group,	 or  pg_shadow),  then	a  standalone
       server must be used to repair it. REINDEX will not process shared cat-
       alogs in multiuser mode.

       For all indexes except the shared system catalogs, REINDEX  is  crash-
       safe  and  transaction-safe.  REINDEX  is  not  crash-safe  for shared
       indexes, which is why this case is disallowed during normal operation.
       If  a  failure  occurs while reindexing one of these catalogs in stan-
       dalone mode, it will not be possible to	restart	 the  regular  server
       until  the  problem  is rectified. (The typical symptom of a partially
       rebuilt shared index is ‘‘index is not a btree’’ errors.)

       Prior to PostgreSQL 7.4, REINDEX TABLE did not  automatically  process
       TOAST  tables,  and so those had to be reindexed by separate commands.
       This is still possible, but redundant.

EXAMPLES
       Recreate the indexes on the table my_table:

       REINDEX TABLE my_table;


       Rebuild a single index:

       REINDEX INDEX my_index;


       Rebuild all system indexes in a particular database, without  trusting
       them to be valid already:

       $ export PGOPTIONS="-P"
       $ psql broken_db
       broken_db=> REINDEX DATABASE broken_db;
       broken_db=> \q


COMPATIBILITY
       There is no REINDEX command in the SQL standard.



SQL - Language Statements	  2008-01-03			    REINDEX()