REINDEX(7)                                                SQL Commands                                                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 sev-
       eral 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 prac-
         tice indexes can become corrupted due to software bugs or hardware failures. REINDEX provides a recovery method.

       o An  index  has  become  ``bloated'',  that  it is 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 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 skipped except in stand-
              alone mode (see below). This form of REINDEX cannot be executed inside a transaction block.

       SYSTEM Recreate all indexes on system catalogs within the current database.  Indexes on user tables  are  not  processed.
              Also,  indexes on shared system catalogs are skipped except in stand-alone mode (see below).  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 impor-
       tant 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 vari-
       able 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.

       If  corruption  is  suspected  in the indexes of any of the shared system catalogs (which are pg_authid, pg_auth_members,
       pg_database, pg_pltemplate, pg_shdepend, pg_shdescription, and pg_tablespace), then a standalone server must be  used  to
       repair it. REINDEX will not process shared catalogs 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 standalone mode, it will not be possible to restart the regular server until the problem is rec-
       tified. (The typical symptom of a partially rebuilt shared index is ``index is not a btree'' errors.)

       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 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.



SQL - Language Statements                                  2011-09-22                                                 REINDEX(7)