REINDEX(7)		PostgreSQL 9.2.24 Documentation		    REINDEX(7)



NAME
       REINDEX - rebuild indexes

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

DESCRIPTION
       REINDEX rebuilds an index using the data stored in the index's table,
       replacing the old copy of the index. There are several scenarios in
       which to use REINDEX:

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

       o   An index has become "bloated", that is it contains many empty or
	   nearly-empty pages. This can occur with B-tree indexes in
	   PostgreSQL under certain uncommon 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
	   Section 23.2, "Routine Reindexing", in the documentation for more
	   information.

       o   You have altered a storage parameter (such as fillfactor) for an
	   index, and wish to ensure that the change has taken full effect.

       o   An index build with the CONCURRENTLY option failed, leaving an
	   "invalid" index. Such indexes are useless but it can be convenient
	   to use REINDEX to rebuild them. Note that REINDEX will not perform
	   a concurrent build. To build the index without interfering with
	   production you should drop the index and reissue the CREATE INDEX
	   CONCURRENTLY command.

PARAMETERS
       INDEX
	   Recreate the specified index.

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

       DATABASE
	   Recreate all indexes within the current database. Indexes on shared
	   system catalogs are also processed. This form of REINDEX cannot be
	   executed inside a transaction block.

       SYSTEM
	   Recreate all indexes on system catalogs within the current
	   database. Indexes on shared system catalogs are included. Indexes
	   on user tables are not processed. This form of REINDEX cannot be
	   executed inside a transaction block.

       name
	   The name of the specific index, table, or database to be reindexed.
	   Index and table names can be schema-qualified. Presently, REINDEX
	   DATABASE and REINDEX SYSTEM can only reindex the current database,
	   so their parameter must match the current database's name.

       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.

       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 might find that server processes are crashing
       immediately 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 server and start a single-user
       PostgreSQL server with the -P option included on its command line.
       Then, REINDEX DATABASE, REINDEX SYSTEM, REINDEX TABLE, or REINDEX INDEX
       can be issued, depending on how much you want to reconstruct. If in
       doubt, use REINDEX SYSTEM to select reconstruction of all system
       indexes in the database. Then quit the single-user server session and
       restart the regular server. See the postgres(1) reference page for more
       information about how to interact with the single-user 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
       might still be wise to prevent other users from connecting to the
       damaged database until repairs have been completed.

       REINDEX is similar to a drop and recreate of the index in that the
       index contents are rebuilt from scratch. However, the locking
       considerations are rather different.  REINDEX locks out writes but not
       reads of the index's parent table. It also takes an exclusive lock on
       the specific index being processed, which will block reads that attempt
       to use that index. In contrast, DROP INDEX momentarily takes an
       exclusive lock on the parent table, blocking both writes and reads. The
       subsequent CREATE INDEX locks out writes but not reads; since the index
       is not there, no read will attempt to use it, meaning that there will
       be no blocking but reads might be forced into expensive sequential
       scans.

       Reindexing a single index or table requires being the owner of that
       index or table. Reindexing a database requires being the owner of the
       database (note that the owner can therefore rebuild indexes of tables
       owned by other users). Of course, superusers can always reindex
       anything.

       Prior to PostgreSQL 8.1, REINDEX DATABASE processed only system
       indexes, not all indexes as one would expect from the name. This has
       been changed to reduce the surprise factor. The old behavior is
       available as REINDEX SYSTEM.

       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
       Rebuild a single index:

	   REINDEX INDEX my_index;

       Rebuild all the indexes on the table my_table:

	   REINDEX TABLE my_table;

       Rebuild all indexes in a particular database, without trusting the
       system indexes 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.



PostgreSQL 9.2.24		  2017-11-06			    REINDEX(7)